Develop Reference

How to make collapsable ConstraintLayout? [duplicate]

I have a View and a RecyclerView housed in a LinearLayout. What I want to achieve is something like this:
https://material.google.com/patterns/scrolling-techniques.html#scrolling-techniques-behavior
Basically when I scroll the RecyclerView up, the View collapses. It expands if I scroll the RecyclerView down.
I've tried various methods but the animation stutters if the finger jerks around a scroll position. It only animates well if the finger does a deliberate scroll movement in one direction. How do I do this correctly?

You have to use Coordinator Layout with the CollapsingToolbarLayout
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipToPadding="false">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar_layout"
android:layout_width="match_parent"
android:layout_height="210dp"
android:stateListAnimator="#animator/appbar_always_elevated" //I put this here because I want to have shadow when is open, but you have to create the xml file.
android:background="#color/WHITE">
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/collapsing_toolbar_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:collapsedTitleTextAppearance="#style/TextAppearance.AppCompat.Widget.ActionBar.Title.Inverse"
app:expandedTitleMarginStart="72dp"
app:expandedTitleTextAppearance="#style/TextAppearance.AppCompat.Widget.ActionBar.Title.Inverse"
app:layout_scrollFlags="scroll|exitUntilCollapsed"> //HERE you should take a look what you want your collapse bar do.
<Here you put the content for you collapse bar, like a ImageView>
<android.support.v7.widget.Toolbar //This is the size of your fixed bar when you collapse, even here you can put a back button, for example
android:id="#+id/app_bar"
android:layout_width="match_parent"
android:layout_height="40dp"
app:layout_collapseMode="pin" />
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<android.support.v4.widget.SwipeRefreshLayout
android:id="#+id/main_home_list_swipe"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior" >
<android.support.v7.widget.RecyclerView
android:id="#+id/main_home_list"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</android.support.design.widget.CoordinatorLayout >
Obs: the comments will give errors if you put on a xml file. Is on propose so you will remember to read hahahah

Try this:-
I also want this kind of animation on custom view and i have achieved it this way.
public class TestActivity extends AppCompatActivity {
private static final int HIDE_THRESHOLD = 20;
//this is you custom layout it is any thing.
LinearLayout customLayout;
private int scrolledDistance = 0;
private boolean controlsVisible = true;
private RecyclerView recyclerView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.your_layout);
recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
scrolledDistance = dy;
if (scrolledDistance > HIDE_THRESHOLD && controlsVisible) {
hideViews();
controlsVisible = false;
} else if (scrolledDistance < -HIDE_THRESHOLD && !controlsVisible) {
showViews();
controlsVisible = true;
}
}
});
}
private void hideViews() {
customLayout.animate().translationY(-customLayout.getHeight()).setInterpolator(new AccelerateInterpolator(2));
}
private void showViews() {
customLayout.animate().translationY(0).setInterpolator(new DecelerateInterpolator(2));
}
}
Edit - 1
for ScrollView try this listener
scrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
#Override
public void onScrollChanged() {
if (scrolledDistance > HIDE_THRESHOLD && controlsVisible) {
hideViews();
controlsVisible = false;
scrolledDistance = 0;
} else if (scrolledDistance < -HIDE_THRESHOLD && !controlsVisible) {
showViews();
controlsVisible = true;
scrolledDistance = 0;
}
}
});
Hope it also helps you...

To achieve toolbar to expand and collapse smoothly you can apply translate animation or use CoordinatorLayout with AppBarLayout and Toolbar.
Animation : First you have to detect scroll up and scroll down on your RecyclerView. To do so you can set “setOnScrollListener” on your RecyclerView. Once you have both scroll up and scroll down, simply apply animation.
Code:
rvHomeList.setOnScrollListener(new RecyclerView.OnScrollListener() {
int verticalOffset;
boolean scrollingUp;
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
if (scrollingUp) {
Log.e("onScrollStateChanged", "UP");
if (verticalOffset > llTop.getHeight()) {
toolbarAnimateHide();
}
} else {
Log.e("onScrollStateChanged", "down");
if (llTop.getTranslationY() < llTop.getHeight() * -0.6 && verticalOffset > llTop.getHeight()) {
toolbarAnimateHide();
} else {
toolbarAnimateShow(verticalOffset);
}
}
}
}
#Override
public final void onScrolled(RecyclerView recyclerView, int dx, int dy) {
verticalOffset += dy;
scrollingUp = dy > 0;
int toolbarYOffset = (int) (dy - llTop.getTranslationY());
llTop.animate().cancel();
if (scrollingUp) {
Log.e("onScrolled", "UP");
if (toolbarYOffset < llTop.getHeight()) {
llTop.setTranslationY(-toolbarYOffset);
} else {
llTop.setTranslationY(-llTop.getHeight());
}
} else {
Log.e("onScrolled", "down");
if (toolbarYOffset < 0) {
llTop.setTranslationY(0);
} else {
llTop.setTranslationY(-toolbarYOffset);
}
}
}
});
Animation Methods:
private void toolbarAnimateShow(final int verticalOffset) {
if (!isShowing) {
isShowing = true;
llTop.animate()
.translationY(0)
.setInterpolator(new LinearInterpolator())
.setDuration(180)
.setListener(new AnimatorListenerAdapter() {
#Override
public void onAnimationStart(Animator animation) {
llTop.setVisibility(View.VISIBLE);
isShowing = false;
}
});
}
}
private void toolbarAnimateHide() {
if (!isHidding) {
isHidding = true;
llTop.animate()
.translationY(-llTop.getHeight())
.setInterpolator(new LinearInterpolator())
.setDuration(180)
.setListener(new AnimatorListenerAdapter() {
#Override
public void onAnimationEnd(Animator animation) {
llTop.setVisibility(View.GONE);
isHidding = false;
}
});
}
}
CoordinatorLayout with AppBarLayout and Toolbar: By using coordinatorLayout with appBarLayout and toolbar, and set the scroll flag used within the attribute app:layout_scrollFlags to achieve the scroll effect. It must be enabled for any scroll effects to take into effect. This flag must be enabled along with enterAlways, enterAlwaysCollapsed, exitUntilCollapsed, or snap.
enterAlways: The view will become visible when scrolling up. This flag is useful in cases when scrolling from the bottom of a list and wanting to expose the Toolbar as soon as scrolling up takes place.
enterAlwaysCollapsed: Normally, when only enterAlways is used, the Toolbar will continue to expand as you scroll down.Assuming enterAlways is declared and you have specified a minHeight, you can also specify enterAlwaysCollapsed. When this setting is used, your view will only appear at this minimum height. Only when scrolling reaches to the top will the view expand to its full height
exitUntilCollapsed: When the scroll flag is set, scrolling down will normally cause the entire content to move.By specifying a minHeight and exitUntilCollapsed, the minimum height of the Toolbar will be reached before the rest of the content begins to scroll and exit from the screen
snap: Using this option will determine what to do when a view only has been partially reduced. If scrolling ends and the view size has been reduced to less than 50% of its original, then this view to return to its original size. If the size is greater than 50% of its sized, it will disappear completely.
Code:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/llBase"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/white"
android:orientation="vertical">
<android.support.design.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1">
<android.support.design.widget.AppBarLayout
android:id="#+id/appbarContainer"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="#dimen/_40sdp"
android:gravity="center"
android:theme="#style/ThemeOverlay.AppCompat.Light"
app:layout_scrollFlags="scroll|enterAlways">
<include
layout="#layout/top_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</android.support.v7.widget.Toolbar>
</android.support.design.widget.AppBarLayout>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
<RelativeLayout
android:id="#+id/rlMain"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"/>
</RelativeLayout>
</android.support.design.widget.CoordinatorLayout>
</LinearLayout>

You need to use CoordinatorLayout to achieve what you want.
You could find all needed information in this tutorial.

Android - How to add parallax effect as bottom sheet covers another view

Using BottomSheetBehavior from the google design library, it looks like the default behavior is for the bottom sheet to "cover" other views in the same CoordinatorLayout as it expands. I can anchor something like a FAB (or other view with an appropriately defined CoordinatorLayout.Behavior) to the top of the sheet and have it slide up as the sheet expands, which is nice, but what I want is to have a view "collapse" as the bottom sheet expands, showing a parallax effect.
This effect in Google Maps is similar to what I'm looking for; it starts as a parallax effect, and then switches back to just having the bottom sheet "cover" the map once a certain scroll position is reached:
One thing I tried (though I suspected from the start it wouldn't work), was setting the upper view's height programmatically in the onSlide call of my BottomSheetBehavior.BottomSheetCallback. This was somewhat successful, but the movement wasn't nearly as smooth as in Google Maps.
If anyone has an idea how the effect is accomplished I would appreciate it a lot!

After a bit more experimenting/research I realized from this post
How to make custom CoordinatorLayout.Behavior with parallax scrolling effect for google MapView? that a big part of my problem was not understanding the parallax effect, which translates views rather than shrinking them. Once I realized that, it was trivial to create a custom behavior that would apply the parallax to my main view when the bottom sheet expanded:
public class CollapseBehavior<V extends ViewGroup> extends CoordinatorLayout.Behavior<V>{
public CollapseBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
public boolean onDependentViewChanged(CoordinatorLayout parent, V child, View dependency) {
if (isBottomSheet(dependency)) {
BottomSheetBehavior behavior = ((BottomSheetBehavior) ((CoordinatorLayout.LayoutParams) dependency.getLayoutParams()).getBehavior());
int peekHeight = behavior.getPeekHeight();
// The default peek height is -1, which
// gets resolved to a 16:9 ratio with the parent
final int actualPeek = peekHeight >= 0 ? peekHeight : (int) (((parent.getHeight() * 1.0) / (16.0)) * 9.0);
if (dependency.getTop() >= actualPeek) {
// Only perform translations when the
// view is between "hidden" and "collapsed" states
final int dy = dependency.getTop() - parent.getHeight();
ViewCompat.setTranslationY(child, dy/2);
return true;
}
}
return false;
}
private static boolean isBottomSheet(#NonNull View view) {
final ViewGroup.LayoutParams lp = view.getLayoutParams();
if (lp instanceof CoordinatorLayout.LayoutParams) {
return ((CoordinatorLayout.LayoutParams) lp)
.getBehavior() instanceof BottomSheetBehavior;
}
return false;
}
}
Then in my layout XML, I set the app:layout_behavior of my main view to be com.mypackage.CollapseBehavior and the app:layout_anchor to be my bottom sheet view so that the onDependentViewChanged callback would trigger. This effect was much smoother than trying to resize the view. I suspect returning to my initial strategy of using a BottomSheetBehavior.BottomSheetCallback would also work similarly to this solution.
Edit: per request, the relevant XML is below. I add a MapFragment into #+id/map_container at runtime, though this should also work with anything you drop into that container like a static image. The LocationListFragment could likewise be replaced with any view or fragment, so long as it still has the BottomSheetBehavior
<android.support.design.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/fragment_coordinator">
<FrameLayout
android:id="#+id/map_container"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="top"
app:layout_anchor="#+id/list_container"
app:layout_behavior="com.mypackage.behavior.CollapseBehavior"/>
<fragment
android:name="com.mypackage.fragment.LocationListFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/list_container"
app:layout_behavior="android.support.design.widget.BottomSheetBehavior"/>
</android.support.design.widget.CoordinatorLayout>

Patrick Grayson's post was very helpful. In my case though, I did need something that resized the map. I adopted the solution above to resize instead of translate. Perhaps others may be looking for a similar solution.
public class CollapseBehavior<V extends ViewGroup> extends CoordinatorLayout.Behavior<V> {
private int pixels = NO_RESIZE_BUFFER; // default value, in case getting a value from resources, bites the dust.
private static final int NO_RESIZE_BUFFER = 200; //The amount of dp to not have the bottom sheet ever push away.
public CollapseBehavior(Context context, AttributeSet attrs)
{
super(context, attrs);
pixels = (int)convertDpToPixel(NO_RESIZE_BUFFER,context);
}
#Override
public boolean onDependentViewChanged(CoordinatorLayout parent, V child, View dependency) {
// child is the map
// dependency is the bottomSheet
if(isBottomSheet(dependency))
{
BottomSheetBehavior behavior = ((BottomSheetBehavior) ((CoordinatorLayout.LayoutParams)dependency.getLayoutParams()).getBehavior());
int peekHeight;
if (behavior != null) {
peekHeight = behavior.getPeekHeight();
}
else
return true;
if(peekHeight > 0) { // Dodge the case where the sheet is hidden.
if (dependency.getTop() >= peekHeight) { // Otherwise we'd completely overlap the map
if(dependency.getTop() >= pixels) { // On resize when we have more than our NO_RESIZE_BUFFER of dp left.
if(dependency.getTop() > 0) { // Don't want to map to be gone completely.
CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) child.getLayoutParams();
params.height = dependency.getTop();
child.setLayoutParams(params);
}
return true;
}
}
}
}
return false;
}
private static float convertDpToPixel(float dp, Context context)
{
float densityDpi = context.getResources().getDisplayMetrics().densityDpi;
return dp * (densityDpi / DisplayMetrics.DENSITY_DEFAULT);
}
private static boolean isBottomSheet(#NonNull View view)
{
final ViewGroup.LayoutParams lp = view.getLayoutParams();
if(lp instanceof CoordinatorLayout.LayoutParams)
{
return ((CoordinatorLayout.LayoutParams) lp).getBehavior() instanceof BottomSheetBehavior;
}
return false;
}
}
And the layout...
<FrameLayout
android:id="#+id/flMap"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="top"
android:layout_margin="0dp"
app:layout_anchor="#+id/persistentBottomSheet"
app:layout_behavior="com.yoursite.yourapp.CollapseBehavior">
<fragment
android:id="#+id/mapDirectionSummary"
android:name="com.google.android.gms.maps.SupportMapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.yoursite.yourapp.YourActivity" />
</FrameLayout>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/persistentBottomSheet"
app:behavior_peekHeight="#dimen/bottom_sheet_peek_height"
app:behavior_hideable="false"
app:layout_behavior="android.support.design.widget.BottomSheetBehavior"
tools:context="com.yoursite.yourapp.YourActivity">
<!-- Whatever you want on the bottom sheet. -->
</android.support.constraint.ConstraintLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="8dp"
app:cardElevation="8dp"
app:cardBackgroundColor="#324">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="56dp"
android:background="?attr/colorPrimary"
android:theme="#style/ThemeOverlay.AppCompat.ActionBar"
app:popupTheme="#style/Theme.AppCompat.Light">
<EditText
android:id="#+id/txtSearch"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#android:color/transparent"
android:ems="10"
android:inputType="text"
android:maxLines="1" />
</android.support.v7.widget.Toolbar>
</android.support.v7.widget.CardView>
</LinearLayout>

How to avoid blocking of scrolling itself when using setNestedScrollingEnabled(false)?

Background
We have quite a complex layout that has CollapsingToolbarLayout in it, together with a RecyclerView at the bottom.
In certain cases, we temporarily disable the expanding/collapsing of the CollapsingToolbarLayout, by calling setNestedScrollingEnabled(boolean) on the RecyclerView.
The problem
This usually works fine.
However, on some (bit rare) cases, slow scrolling on the RecyclerView gets semi-blocked, meaning it tries to scroll back when scrolling down. It's as if it has 2 scrolling that fight each other (scroll up and scroll down):
The code to trigger this is as such:
res/layout/activity_scrolling.xml
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="com.example.user.myapplication.ScrollingActivity">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar"
android:layout_width="match_parent"
android:layout_height="#dimen/app_bar_height"
android:fitsSystemWindows="true"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/toolbar_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:layout_collapseMode="pin"
app:popupTheme="#style/AppTheme.PopupOverlay"/>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<android.support.v7.widget.RecyclerView
android:id="#+id/nestedView"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_anchor="#id/app_bar"
app:layout_anchorGravity="bottom|end">
<Button
android:id="#+id/disableNestedScrollingButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="disable"/>
<Button
android:id="#+id/enableNestedScrollingButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="enable"
/>
</LinearLayout>
</android.support.design.widget.CoordinatorLayout>
ScrollingActivity.java
public class ScrollingActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_scrolling);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
final RecyclerView nestedView = (RecyclerView) findViewById(R.id.nestedView);
findViewById(R.id.disableNestedScrollingButton).setOnClickListener(new OnClickListener() {
#Override
public void onClick(final View v) {
nestedView.setNestedScrollingEnabled(false);
}
});
findViewById(R.id.enableNestedScrollingButton).setOnClickListener(new OnClickListener() {
#Override
public void onClick(final View v) {
nestedView.setNestedScrollingEnabled(true);
}
});
nestedView.setLayoutManager(new LinearLayoutManager(this));
nestedView.setAdapter(new Adapter() {
#Override
public ViewHolder onCreateViewHolder(final ViewGroup parent, final int viewType) {
return new ViewHolder(LayoutInflater.from(parent.getContext()).inflate(
android.R.layout.simple_list_item_1,
parent,
false)) {
};
}
#Override
public void onBindViewHolder(final ViewHolder holder, final int position) {
((TextView) holder.itemView.findViewById(android.R.id.text1)).setText("item " + position);
}
#Override
public int getItemCount() {
return 100;
}
});
}
}
What I've tried
At first I thought it's because of something else (I thought it's a weird combination with DrawerLayout), but then I've found a minimal sample to show it, and it's just as I thought: it's all because of the setNestedScrollingEnabled.
I tried to report about this on Google's website (here), hoping it will get fixed if it's a real bug. If you wish to try it out, or watch the videos of the issue, go there, as I can't upload them all here (too large and too many files).
I've also tried to use special flags as instructed on other posts (examples: here, here, here, here and here) , but none helped. In fact each of them had an issue, whether it's staying in expanded mode, or scrolling in a different way than what I do.
The questions
Is this a known issue? Why does it happen?
Is there a way to overcome this?
Is there perhaps an alternative to calling this function of setNestedScrollingEnabled ? One without any issues of scrolling or locking the state of the CollapsingToolbarLayout ?

This is an alternate approach to achieving the same goal as this answer. While that answer used Reflection, this answer does not, but the reasoning remains the same.
Why is this happening?
The problem is that RecyclerView sometimes uses a stale value for the member variable mScrollOffset. mScrollOffset is set in only two places in RecyclerView: dispatchNestedPreScroll and dispatchNestedScroll. We are only concerned with dispatchNestedPreScroll. This method is invoked by RecyclerView#onTouchEvent when it handles MotionEvent.ACTION_MOVE events.
The following is from the documentation for dispatchNestedPreScroll.
dispatchNestedPreScroll
boolean dispatchNestedPreScroll (int dx,
int dy,
int[] consumed,
int[] offsetInWindow)
Dispatch one step of a nested scroll in progress before this view consumes any portion of it.
Nested pre-scroll events are to nested scroll events what touch intercept is to touch. dispatchNestedPreScroll offers an opportunity for the parent view in a nested scrolling operation to consume some or all of the scroll operation before the child view consumes it.
...
offsetInWindow int: Optional. If not null, on return this will contain the offset in local view coordinates of this view from before this operation to after it completes. View implementations may use this to adjust expected input coordinate tracking.
offsetInWindow is actually an int[2] with the second index representing the y shift to be applied to the RecyclerView due to nested scrolling.
RecyclerView#DispatchNestedPrescroll resolves to a method with the same name in NestedScrollingChildHelper.
When RecyclerView calls dispatchNestedPreScroll,
mScrollOffset is used as the offsetInWindow argument. So any changes made to offsetInWindow directly updates mScrollOffset. dispatchNestedPreScroll updates mScrollOffset as long as nested scrolling is in effect. If nested scrolling is not in effect, then mScrollOffset is not updated and proceeds with the value that was last set by dispatchNestedPreScroll. Thus, when nested scrolling is turned off, the value of mScrollOffset becomes immediately stale but RecyclerView continues to use it.
The correct value of mScrollOffset[1] upon return from dispatchNestedPreScroll is the amount to adjust for input coordinate tracking (see above). In RecyclerView the following lines adjusts the y touch coordinate:
mLastTouchY = y - mScrollOffset[1];
If mScrollOffset[1] is, let's say, -30 (because it is stale and should be zero) then mLastTouchY will be off by +30 pixels (--30=+30). The effect of this miscalculation is that it will appear that the touch occurred further down the screen than it really did. So, a slow downward scroll will actually scrolls up and an upward scroll will scroll faster. (If a downward scroll is fast enough to overcome this 30px barrier, then downward scrolling will occur but more slowly than it should.) Upward scrolling will be overly quick since the app thinks more space has been covered.
mScrollOffset will continue as a stale variable until nested scrolling is turned on and dispatchNestedPreScroll once again reports the correct value in mScrollOffset.
Approach
Since mScrollOffset[1] has a stale value under certain circumstances, the goal is to set it to the correct value under those circumstances. This value should be zero when nested scrolling is not taking place, i.e., When the AppBar is expanded or collapsed. Unfortunately, mScrollOffset is local to RecyclerView and there is no setter for it. To gain access to mScrollOffset without resorting to Reflection, a custom RecyclerView is created that overrides dispatchNestedPreScroll. The fourth agument is offsetInWindow which is the variable we need to change.
A stale mScrollOffset occurs whenever nested scrolling is disabled for the RecyclerView. An additional condition we will impose is that the AppBar must be idle so we can safely say that mScrollOffset[1] should be zero. This is not an issue since the CollapsingToolbarLayout specifies snap in the scroll flags.
In the sample app, ScrollingActivity has been modified to record when the AppBar is expanded and closed. A callback has also been created (clampPrescrollOffsetListener) that will return true when our two conditions are met. Our overridden dispatchNestedPreScroll will invoke this callback and clamp mScrollOffset[1] to zero on a true response.
The updated source file for ScrollingActivity is presented below as is the custom RecyclerView - MyRecyclerView.
The XML layout file must be changed to reflect the custom MyRecyclerView.
ScrollingActivity
public class ScrollingActivity extends AppCompatActivity
implements MyRecyclerView.OnClampPrescrollOffsetListener {
private CollapsingToolbarLayout mCollapsingToolbarLayout;
private AppBarLayout mAppBarLayout;
private MyRecyclerView mNestedView;
// This variable will be true when the app bar is completely open or completely collapsed.
private boolean mAppBarIdle = true;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_scrolling);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
mNestedView = (MyRecyclerView) findViewById(R.id.nestedView);
mAppBarLayout = (AppBarLayout) findViewById(R.id.app_bar);
mCollapsingToolbarLayout = (CollapsingToolbarLayout) findViewById(R.id.toolbar_layout);
// Set the listener for the patch code.
mNestedView.setOnClampPrescrollOffsetListener(this);
// Listener to determine when the app bar is collapsed or fully open (idle).
mAppBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
#Override
public final void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
mAppBarIdle = verticalOffset == 0
|| verticalOffset <= appBarLayout.getTotalScrollRange();
}
});
findViewById(R.id.disableNestedScrollingButton).setOnClickListener(new OnClickListener() {
#Override
public void onClick(final View v) {
// If the AppBar is fully expanded or fully collapsed (idle), then disable
// expansion and apply the patch; otherwise, set a flag to disable the expansion
// and apply the patch when the AppBar is idle.
setExpandEnabled(false);
}
});
findViewById(R.id.enableNestedScrollingButton).setOnClickListener(new OnClickListener() {
#Override
public void onClick(final View v) {
setExpandEnabled(true);
}
});
mNestedView.setLayoutManager(new LinearLayoutManager(this));
mNestedView.setAdapter(new Adapter() {
#Override
public ViewHolder onCreateViewHolder(final ViewGroup parent, final int viewType) {
return new ViewHolder(LayoutInflater.from(parent.getContext()).inflate(
android.R.layout.simple_list_item_1,
parent,
false)) {
};
}
#Override
public void onBindViewHolder(final ViewHolder holder, final int position) {
((TextView) holder.itemView.findViewById(android.R.id.text1)).setText("item " + position);
}
#Override
public int getItemCount() {
return 100;
}
});
}
private void setExpandEnabled(boolean enabled) {
mNestedView.setNestedScrollingEnabled(enabled);
}
// Return "true" when the app bar is idle and nested scrolling is disabled. This is a signal
// to the custom RecyclerView to clamp the y prescroll offset to zero.
#Override
public boolean clampPrescrollOffsetListener() {
return mAppBarIdle && !mNestedView.isNestedScrollingEnabled();
}
private static final String TAG = "ScrollingActivity";
}
MyRecyclerView
public class MyRecyclerView extends RecyclerView {
private OnClampPrescrollOffsetListener mPatchListener;
public MyRecyclerView(Context context) {
super(context);
}
public MyRecyclerView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public MyRecyclerView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
// Just a call to super plus code to force offsetInWindow[1] to zero if the patchlistener
// instructs it.
#Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
boolean returnValue;
int currentOffset;
returnValue = super.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
currentOffset = offsetInWindow[1];
Log.d(TAG, "<<<<dispatchNestedPreScroll: " + currentOffset);
if (mPatchListener.clampPrescrollOffsetListener() && offsetInWindow[1] != 0) {
Log.d(TAG, "<<<<dispatchNestedPreScroll: " + currentOffset + " -> 0");
offsetInWindow[1] = 0;
}
return returnValue;
}
public void setOnClampPrescrollOffsetListener(OnClampPrescrollOffsetListener patchListener) {
mPatchListener = patchListener;
}
public interface OnClampPrescrollOffsetListener {
boolean clampPrescrollOffsetListener();
}
private static final String TAG = "MyRecyclerView";
}

Actually, you might be looking at the problem in the wrong way.
The only thing you need is to set the Toolbar flags accordingly. You don't really anything else so I would say that your layout should be simplified to:
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="com.example.user.myapplication.ScrollingActivity">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar"
android:layout_width="match_parent"
android:layout_height="#dimen/app_bar_height"
android:fitsSystemWindows="true"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="#style/AppTheme.PopupOverlay"
app:title="Title" />
</android.support.design.widget.AppBarLayout>
<android.support.v7.widget.RecyclerView
android:id="#+id/nestedView"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_anchor="#id/app_bar"
app:layout_anchorGravity="bottom|end">
<Button
android:id="#+id/disableNestedScrollingButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="disable"/>
<Button
android:id="#+id/enableNestedScrollingButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="enable"
/>
</LinearLayout>
</android.support.design.widget.CoordinatorLayout>
Then when you wish to disable the collapsing just set your toolbar flags:
// To disable collapsing
AppBarLayout.LayoutParams params = (AppBarLayout.LayoutParams) toolbar.getLayoutParams();
params.setScrollFlags(AppBarLayout.LayoutParams.SCROLL_FLAG_SNAP);
toolbar.setLayoutParams(params);
And to enable
// To enable collapsing
AppBarLayout.LayoutParams params = (AppBarLayout.LayoutParams) toolbar.getLayoutParams();
params.setScrollFlags(AppBarLayout.LayoutParams.SCROLL_FLAG_SCROLL|AppBarLayout.LayoutParams.SCROLL_FLAG_ENTER_ALWAYS);
toolbar.setLayoutParams(params);
Hold a reference to the layout params if you are changing instead of getting it all the time.
If you need to have the CollapsingToolbarLayout get from and set the LayoutParams to that View instead, update the flags the same way but now adding the appBarLayout.setExpanded(true/false)
Note: Using the setScrollFlags clears all previous flags, so be careful and set all required flags when using this method.

As #Moinkhan points out, you could try wrapping the RecyclerView and next elements in a NestedScrollView like this, this should resolve your problem of scrolling alongside with your collapsing toolbar layout:
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="com.example.user.myapplication.ScrollingActivity">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar"
android:layout_width="match_parent"
android:layout_height="#dimen/app_bar_height"
android:fitsSystemWindows="true"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/toolbar_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:layout_collapseMode="pin"
app:popupTheme="#style/AppTheme.PopupOverlay"/>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="fill_vertical"
android:fillViewport="true"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:id="#+id/nestedView"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"/>
</RelativeLayout>
</android.support.v4.widget.NestedScrollView>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_anchor="#id/app_bar"
app:layout_anchorGravity="bottom|end">
<Button
android:id="#+id/disableNestedScrollingButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="disable"/>
<Button
android:id="#+id/enableNestedScrollingButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="enable"
/>
</LinearLayout>
</android.support.design.widget.CoordinatorLayout>
In case the contents of the recyclerview are not displayed you can follow this thread to solve that issue How to use RecyclerView inside NestedScrollView?.
Hope it helps.

inside the recycler view, to scrolling smooth
android:nestedScrollingEnabled="false"
to overlap the cardView in the toolbar
app:behavior_overlapTop = "24dp"
Try this code for CollapsingToolbar:
<android.support.design.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/background"
android:fitsSystemWindows="true">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar"
android:layout_width="match_parent"
android:layout_height="#dimen/app_bar_height"
android:fitsSystemWindows="true"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/toolbar_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:layout_collapseMode="pin"
app:popupTheme="#style/AppTheme.PopupOverlay"
app:title="Title" />
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:background="#android:color/transparent"
app:behavior_overlapTop="#dimen/behavior_overlap_top"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
<LinearLayout
android:id="#+id/linearLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v7.widget.RecyclerView
android:id="#+id/recycler_view
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="#dimen/text_min_padding"
android:nestedScrollingEnabled="false"
android:scrollbarSize="2dp"
android:scrollbarStyle="outsideInset"
android:scrollbarThumbVertical="#color/colorAccent"
android:scrollbars="vertical" />
</LinearLayout>
</android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinatorLayout>
Screenshot

I had to solve a similar issue and did it using a custom behaviour on the AppBarLayout. Everything works great.
By overriding onStartNestedScroll in the custom behaviour it is possible to block to collapsing toolbar layout from expanding or collapsing while keeping the scroll view (NestedScrollView) in my case, working as expected. I explained the details here, hope it helps.
private class AppBarLayoutBehavior : AppBarLayout.Behavior() {
var canDrag = true
var acceptsNestedScroll = true
init {
setDragCallback(object : AppBarLayout.Behavior.DragCallback() {
override fun canDrag(appBarLayout: AppBarLayout): Boolean {
// Allow/Do not allow dragging down/up to expand/collapse the layout
return canDrag
}
})
}
override fun onStartNestedScroll(parent: CoordinatorLayout,
child: AppBarLayout,
directTargetChild: View,
target: View,
nestedScrollAxes: Int,
type: Int): Boolean {
// Refuse/Accept any nested scroll event
return acceptsNestedScroll
}}

Use following code, it works fine for me:
lockAppBarClosed();
ViewCompat.setNestedScrollingEnabled(recyclerView, false); // to lock the CollapsingToolbarLayout
and implement the following methods:
private void setAppBarDragging(final boolean isEnabled) {
CoordinatorLayout.LayoutParams params =
(CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
AppBarLayout.Behavior behavior = new AppBarLayout.Behavior();
behavior.setDragCallback(new AppBarLayout.Behavior.DragCallback() {
#Override
public boolean canDrag(AppBarLayout appBarLayout) {
return isEnabled;
}
});
params.setBehavior(behavior);
}
public void unlockAppBarOpen() {
appBarLayout.setExpanded(true, false);
appBarLayout.setActivated(true);
setAppBarDragging(false);
}
public void lockAppBarClosed() {
appBarLayout.setExpanded(false, false);
appBarLayout.setActivated(false);
setAppBarDragging(false);
}

I believe that this problem is related to the collapsing toolbar snapping into place (either closed or open) and leaving a vertical offset variable (mScrollOffset[1] in RecyclerView) with a non-zero value that subsequently biases the scroll - slowing or reversing the scroll in one direction and speeding it up in the other. This variable only seems to be set in NestedScrollingChildHelper if nested scrolling is enabled. So, whatever value mScrollOffset[1] has goes unchanged once nest scrolling is disabled.
To reliably reproduce this issue, you can cause the toolbar to snap into place then immediately click disable. See this video for a demonstration. I believe, that the magnitude of the issue varies by how much "snapping" occurs.
If I drag the toolbar to the fully open or closed position and don't let it "snap", then I have not been able to reproduce this problem and mScrollOffset[1] is set to zero which I think is the right value. I have also reproduced the problem by removing snap from the layout_scrollFlags of the collapsing toolbar in the layout and placing the toolbar in a partially open state.
If you want to play around with this, you can put your demo app into debug mode and observe the value of mScrollOffset[1] in RecyclerView#onTouchEvent. Also take a look at NestedScrollingChildHelper's dispatchNestedScroll and dispatchNestedPreScroll methods to see how the offset is set only when nested scrolling is enabled.
So, how to fix this? mScrollOffset is private toRecyclerView and it is not immediately obvious how to subclass anything to change the value of mScrollOffset[1]. That would leave Reflection, but that may not be desirable to you. Maybe another reader has an idea about how to approach this or knows of some secret sauce. I will repost if anything occurs to me.
Edit: I have provided a new ScrollingActivity.java class that overcomes this issue. It does use reflection and applies a patch to set mScrollOffset[1] of RecyclerView to zero when the disable scroll button has been pressed and the AppBar is idle. I have done some preliminary testing and it is working. Here is the gist. (See updated gist below.)
Second edit: I was able to get the toolbar to snap in funny ways and get stuck in the middle without the patch, so it doesn't look like the patch is causing that particular issue. I can get the toolbar to bounce from fully open to collapsed by scrolling down fast enough in the unpatched app.
I also took another look at what the patch is doing and I think that it will behave itself: The variable is private and referred to only in one place after scrolling is turned off. With scrolling enabled, the variable is always reset before use. The real answer is for Google to fix this problem. Until they do, I think this may be the closest you can get to an acceptable work-around with this particular design. (I have posted an updated gist that addresses potential issues with a quick click-around leaving switches in a potential unsuitable state.)
Regardless, the underlying issue has been identified and you have a reliable way to reproduce the problem, so you can more easily verify other proposed solutions.
I hope this helps.

I want to present a nice alternative, mainly based on the one here :
AppBarLayoutEx.kt
class AppBarLayoutEx : AppBarLayout {
private var isAppBarExpanded = true
private val behavior = AppBarLayoutBehavior()
private var onStateChangedListener: (Boolean) -> Unit = {}
var enableExpandAndCollapseByDraggingToolbar: Boolean
get() = behavior.canDrag
set(value) {
behavior.canDrag = value
}
var enableExpandAndCollapseByDraggingContent: Boolean
get() = behavior.acceptsNestedScroll
set(value) {
behavior.acceptsNestedScroll = value
}
constructor(context: Context) : super(context)
constructor(context: Context, attrs: AttributeSet) : super(context, attrs)
init {
addOnOffsetChangedListener(
AppBarLayout.OnOffsetChangedListener { _, verticalOffset ->
isAppBarExpanded = verticalOffset == 0
onStateChangedListener(isAppBarExpanded)
})
}
override fun setLayoutParams(params: ViewGroup.LayoutParams?) {
super.setLayoutParams(params)
(params as CoordinatorLayout.LayoutParams).behavior = behavior
}
fun toggleExpandedState() {
setExpanded(!isAppBarExpanded, true)
}
fun setOnExpandAndCollapseListener(onStateChangedListener: (Boolean) -> Unit) {
this.onStateChangedListener = onStateChangedListener
}
private class AppBarLayoutBehavior : AppBarLayout.Behavior() {
var canDrag = true
var acceptsNestedScroll = true
init {
setDragCallback(object : AppBarLayout.Behavior.DragCallback() {
override fun canDrag(appBarLayout: AppBarLayout) = canDrag
})
}
override fun onStartNestedScroll(parent: CoordinatorLayout, child: AppBarLayout, directTargetChild: View,
target: View, nestedScrollAxes: Int, type: Int) = acceptsNestedScroll
}
}
Usage: besides using it in the layout XML file, you can disable/enable the expanding of it using:
appBarLayout.enableExpandAndCollapseByDraggingToolbar = true/false
appBarLayout.enableExpandAndCollapseByDraggingContent = true/false

Android toolbar elevation when scrolling

I try to implement a search bar like in google maps android app:
When the recycler view is in its initial state, the toolbar has no elevation. Only when the users starts scrolling the elevation becomes visible. And the search bar (toolbar) never collapses. Here is what I tried to replicate this:
<android.support.design.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<android.support.v7.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<android.support.design.widget.AppBarLayout
android:id="#+id/appBarLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="64dp">
<!-- content -->
</android.support.v7.widget.Toolbar>
</android.support.design.widget.AppBarLayout>
</android.support.design.widget.CoordinatorLayout>
And here you can see the result:
So the problem with my solution is, that the elevation of the toolbar is always visible. But I want it to appear only when the recycler view scrolls behind it. Is there anything from the design support library that enables such behavior as seen in the google maps app?
I am using
com.android.support:appcompat-v7:23.2.0
com.android.support:design:23.2.0

The accepted answer is outdated. Now there is inbuilt functionality to do this. I am pasting the whole layout code so it will help you to understand.
You just need to use CoordinatorLayout with AppBarLayout. This design pattern is called Lift On Scroll and can be implemented by setting app:liftOnScroll="true" on your AppBarLayout.
Note: the liftOnScroll attribute requires that you apply the #string/appbar_scrolling_view_behavior layout_behavior to your scrolling view (e.g., NestedScrollView, RecyclerView, etc.).
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:background="#color/default_background">
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:liftOnScroll="true">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#color/default_background" />
</com.google.android.material.appbar.AppBarLayout>
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/list_recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="#+id/appbar"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
android:orientation="vertical" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
Refered this documentation https://github.com/material-components/material-components-android/blob/master/docs/components/AppBarLayout.md

EDIT As pointed out in the comments, my answer is now outdated, see https://stackoverflow.com/a/58272283/4291272
Whether you are using a CoordinatorLayout or not, a RecyclerView.OnScrollListener seems like the right way to go as far as the elevation is concerned. However, from my experience recyclerview.getChild(0).getTop() is not reliable and should not be used for determining the scrolling state. Instead, this is what's working:
private static final int SCROLL_DIRECTION_UP = -1;
// ...
// Put this into your RecyclerView.OnScrollListener > onScrolled() method
if (recyclerview.canScrollVertically(SCROLL_DIRECTION_UP)) {
// Remove elevation
toolbar.setElevation(0f);
} else {
// Show elevation
toolbar.setElevation(50f);
}
Be sure to assign a LayoutManager to your RecyclerView or the call of canScrollVertically may cause a crash!

This is a good question but none of the existing answers are good enough. Calling getTop() is absolutely not recommended as it's very unreliable. If you look at newer versions of Google apps that follow Material Design Refresh (2018) guidelines, they hide the elevation at the beginning and immediately add it as user scrolls down and hide it again as user scrolls and reaches the top again.
I managed to achieve the same effect using the following:
val toolbar: android.support.v7.widget.Toolbar? = activity?.findViewById(R.id.toolbar);
recyclerView?.addOnScrollListener(object: RecyclerView.OnScrollListener() {
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy);
if(toolbar == null) {
return;
}
if(!recyclerView.canScrollVertically(-1)) {
// we have reached the top of the list
toolbar.elevation = 0f
} else {
// we are not at the top yet
toolbar.elevation = 50f
}
}
});
This works perfectly with vertical recycler views (even with tab view or other recycler views inside them);
A couple of important notes:
Here I'm doing this inside a fragment hence activity?.findViewById...
If your Toolbar is nested inside an AppBarLayout, then instead of applying elevation to Toolbar, you should apply it to the AppBarLayout.
You should add android:elevation="0dp" and app:elevation="0dp" attributes to your Toolbar or AppBarLayout so that the recycler view doesn't have elevation at the beginning.

I have a RecyclerView in my fragment. I could achieve similar effect using code below:
It is not the Smartest way and you can wait for better answers.
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Initial Elevation
final Toolbar toolbar = (Toolbar) getActivity().findViewById(R.id.toolbar);
if(toolbar!= null)
toolbar.setElevation(0);
// get initial position
final int initialTopPosition = mRecyclerView.getTop();
// Set a listener to scroll view
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if(toolbar!= null && mRecyclerView.getChildAt(0).getTop() < initialTopPosition ) {
toolbar.setElevation(50);
} else {
toolbar.setElevation(0);
}
}
});
}

I found this when page when I wanted to do something similar, but for a more complex View Hierarchy.
After some research, I was able to get the same effect using a custom behavior. This works for any view in a coordinator layout (given that there's a nested scroll element such as RecyclerView or NestedScrollView)
Note: This only works on API 21 and above as ViewCompat.setElevation does not seem to have any effect pre lollipop and AppBarLayout#setTargetElevation is deprecated
ShadowScrollBehavior.java
public class ShadowScrollBehavior extends AppBarLayout.ScrollingViewBehavior
implements View.OnLayoutChangeListener {
int totalDy = 0;
boolean isElevated;
View child;
public ShadowScrollBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
public boolean layoutDependsOn(CoordinatorLayout parent, View child,
View dependency) {
parent.addOnLayoutChangeListener(this);
this.child = child;
return super.layoutDependsOn(parent, child, dependency);
}
#Override
public boolean onStartNestedScroll(#NonNull CoordinatorLayout coordinatorLayout,
#NonNull View child, #NonNull View directTargetChild,
#NonNull View target, int axes, int type) {
// Ensure we react to vertical scrolling
return axes == ViewCompat.SCROLL_AXIS_VERTICAL ||
super.onStartNestedScroll(coordinatorLayout, child, directTargetChild,
target, axes, type);
}
#Override
public void onNestedPreScroll(#NonNull CoordinatorLayout coordinatorLayout,
#NonNull View child, #NonNull View target,
int dx, int dy, #NonNull int[] consumed, int type) {
totalDy += dy;
if (totalDy <= 0) {
if (isElevated) {
ViewGroup parent = (ViewGroup) child.getParent();
if (parent != null) {
TransitionManager.beginDelayedTransition(parent);
ViewCompat.setElevation(child, 0);
}
}
totalDy = 0;
isElevated = false;
} else {
if (!isElevated) {
ViewGroup parent = (ViewGroup) child.getParent();
if (parent != null) {
TransitionManager.beginDelayedTransition(parent);
ViewCompat.setElevation(child, dp2px(child.getContext(), 4));
}
}
if (totalDy > target.getBottom())
totalDy = target.getBottom();
isElevated = true;
}
super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type);
}
private float dp2px(Context context, int dp) {
Resources r = context.getResources();
float px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, r.getDisplayMetrics());
return px;
}
#Override
public void onLayoutChange(View view, int i, int i1, int i2, int i3, int i4, int i5, int i6, int i7) {
totalDy = 0;
isElevated = false;
ViewCompat.setElevation(child, 0);
}
}
my_activity_layout.xml
<android.support.design.widget.CoordinatorLayout
android:fitsSystemWindows="true"
android:layout_height="match_parent"
android:layout_width="match_parent">
<android.support.v7.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_height="match_parent"
android:layout_width="match_parent" />
<android.support.design.widget.AppBarLayout
android:id="#+id/appBarLayout"
android:layout_height="wrap_content"
android:layout_width="match_parent"
app:layout_behavior="com.myapp.ShadowScrollBehavior">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_height="64dp"
android:layout_width="match_parent">
<!-- content -->
</android.support.v7.widget.Toolbar>
</android.support.design.widget.AppBarLayout>
</android.support.design.widget.CoordinatorLayout>

If you use CoordinatorLayout you dont need any extra code to make this work by yourself just some setup on style and layout XML, check this:
Your app style should use a MaterialCompoment style, like src/main/res/values/styles.xml.
Setup you AppBarLayout:
Use any MaterialCompoments style for this component like: Widget.MaterialComponents.AppBarLayout.Surface.
Set app:liftOnScroll="true" to enable the automatic elevation based on scroll.
Setup your scrolling view:
Set app:layout_behavior="#string/appbar_scrolling_view_behavior.
https://github.com/danielgomezrico/spike-appbarlayout-toolbar-automatic-elevation

Android - footer scrolls off screen when used in CoordinatorLayout

I have an AppBarLayout that scrolls off screen when scrolling a RecyclerView.
Below the RecyclerView there is a RelativeLayout that is a footer.
The footer is shown only after scrolling up - it behave like it has
layout_scrollFlags="scroll|enterAlways"
but it doesn't have any scroll flags - is it a bug or am I doing something wrong? I want it to be always visible
before scroll
after scroll
Update
opened a google issue on this - it was marked 'WorkingAsIntended' this still doesn't help because I want a working solution of a footer inside a fragment.
Update 2
you can find the activity and the fragment xmls here -
note that if line 34 in activity.xml - the line containing app:layout_behavior="#string/appbar_scrolling_view_behavior" is commented out the text end is visible from the start - otherwise, it is visible only after scrolling up

I use a simplified version of Learn OpenGL ES's solution (https://stackoverflow.com/a/33396965/778951) -- which improves on Noa's solution (https://stackoverflow.com/a/31140112/1317564). It works fine for my simple quick-return toolbar above a TabLayout with footer buttons in each tab's ViewPager content.
Just set the FixScrollingFooterBehavior as the layout_behavior on the View/ViewGroup you want to keep aligned at the bottom of the screen.
Layout:
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?android:attr/actionBarSize"
android:minHeight="?android:attr/actionBarSize"
app:title="Foo"
app:layout_scrollFlags="scroll|enterAlways|snap"
/>
<android.support.design.widget.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabMode="fixed"/>
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="#+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="com.spreeza.shop.ui.widgets.FixScrollingFooterBehavior"
/>
</android.support.design.widget.CoordinatorLayout>
Behavior:
public class FixScrollingFooterBehavior extends AppBarLayout.ScrollingViewBehavior {
private AppBarLayout appBarLayout;
public FixScrollingFooterBehavior() {
super();
}
public FixScrollingFooterBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
public boolean onDependentViewChanged(CoordinatorLayout parent, View child, View dependency) {
if (appBarLayout == null) {
appBarLayout = (AppBarLayout) dependency;
}
final boolean result = super.onDependentViewChanged(parent, child, dependency);
final int bottomPadding = calculateBottomPadding(appBarLayout);
final boolean paddingChanged = bottomPadding != child.getPaddingBottom();
if (paddingChanged) {
child.setPadding(
child.getPaddingLeft(),
child.getPaddingTop(),
child.getPaddingRight(),
bottomPadding);
child.requestLayout();
}
return paddingChanged || result;
}
// Calculate the padding needed to keep the bottom of the view pager's content at the same location on the screen.
private int calculateBottomPadding(AppBarLayout dependency) {
final int totalScrollRange = dependency.getTotalScrollRange();
return totalScrollRange + dependency.getTop();
}
}

Update
The solution below doesn't work for 5.1 as it works in 5 - instead of getTop use getTranslationY in any of the calculations you do.
layout.getTop()-->(int)layout.getTranslationY()
appbar.getTop()+toolbar.getHeight()-->(int)(appbar.getTranslationY()+toolbar.getHeight())
Update 2
with the new support library - 22.2.1 - there is no diff between 5.1 and prev versions, you should only use getTop and ignore the previous update in this answer
Original solution
After looking into many directions turns out the solution is actually simple - add paddingBottom to the fragment and adjust it as the page scrolls.
The padding is needed to cover for the changes in the toolbar y position - the coordinator layout is moving the entire page up and down as the toolbar disappears and reappears.
This can be achieved by extending AppBarLayout.ScrollingViewBehavior and setting this as the behavior of the fragment element of the activity.
Here are the basics of the code - it works for an activity with only a toolbar - you can replace it with appbar.getTop() + toolbar.getHeight() and this will work better if your appbar includes tabs.
activity.xml
<android.support.design.widget.CoordinatorLayout
android:id="#+id/main"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:elevation="3dp"
app:elevation="3dp">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:layout_scrollFlags="scroll|enterAlways"
/>
</android.support.design.widget.AppBarLayout>
<fragment
android:id="#+id/fragment"
android:name="com.example.noa.footer2.MainActivityFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="com.example.noa.footer2.MyBehavior"
tools:layout="#layout/fragment"/>
</android.support.design.widget.CoordinatorLayout>
fragment.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="48dp"
android:background="#android:color/holo_green_dark"
tools:context=".MainActivityFragment">
<android.support.v7.widget.RecyclerView
android:id="#+id/list"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#null"/>
<View
android:layout_width="match_parent"
android:layout_height="100dp"
android:layout_alignParentBottom="true"
android:background="#android:color/holo_red_light"/>
</RelativeLayout>
MainActivityFragment#onActivityCreated
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
CoordinatorLayout.LayoutParams lp = (LayoutParams) getView().getLayoutParams();
MyBehavior behavior = (MyBehavior) lp.getBehavior();
behavior.setLayout(getView());
}
MyBehavior
public class MyBehavior extends AppBarLayout.ScrollingViewBehavior {
private View layout;
public MyBehavior() {
}
public MyBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
public boolean onDependentViewChanged(CoordinatorLayout parent, View child, View dependency) {
boolean result = super.onDependentViewChanged(parent, child, dependency);
if (layout != null) {
layout.setPadding(layout.getPaddingLeft(), layout.getPaddingTop(), layout
.getPaddingRight(), layout.getTop());
}
return result;
}
public void setLayout(View layout) {
this.layout = layout;
}
}

I started out with Noa's solution (https://stackoverflow.com/a/31140112/1317564) and it worked for finger drags, but I was running into trouble with flings. After spending some time to trace the method calls and trying out different ideas, here is the solution I ended up with:
// Workaround for https://code.google.com/p/android/issues/detail?id=177195
// Based off of solution originally found here: https://stackoverflow.com/a/31140112/1317564
#SuppressWarnings("unused")
public class CustomScrollingViewBehavior extends AppBarLayout.ScrollingViewBehavior {
private AppBarLayout appBarLayout;
private boolean onAnimationRunnablePosted = false;
#SuppressWarnings("unused")
public CustomScrollingViewBehavior() {
}
#SuppressWarnings("unused")
public CustomScrollingViewBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, View child, View directTargetChild, View target, int nestedScrollAxes) {
if (appBarLayout != null) {
// We need to check from when a scroll is started, as we may not have had the chance to update the layout at
// the start of a scroll or fling event.
startAnimationRunnable(child, appBarLayout);
}
return super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, nestedScrollAxes);
}
#Override
public boolean onMeasureChild(CoordinatorLayout parent, final View child, int parentWidthMeasureSpec, int widthUsed,
int parentHeightMeasureSpec, int heightUsed) {
if (appBarLayout != null) {
final int bottomPadding = calculateBottomPadding(appBarLayout);
if (bottomPadding != child.getPaddingBottom()) {
// We need to update the padding in onMeasureChild as otherwise we won't have the correct padding in
// place when the view is flung, and the changes done in onDependentViewChanged will only take effect on
// the next animation frame, which means it will be out of sync with the new scroll offset. This is only
// needed when the view is flung -- when dragged with a finger, things work fine with just
// implementing onDependentViewChanged().
child.setPadding(child.getPaddingLeft(), child.getPaddingTop(), child.getPaddingRight(), bottomPadding);
}
}
return super.onMeasureChild(parent, child, parentWidthMeasureSpec, widthUsed, parentHeightMeasureSpec, heightUsed);
}
#Override
public boolean onDependentViewChanged(CoordinatorLayout parent, final View child, final View dependency) {
if (appBarLayout == null)
appBarLayout = (AppBarLayout) dependency;
final boolean result = super.onDependentViewChanged(parent, child, dependency);
final int bottomPadding = calculateBottomPadding(appBarLayout);
final boolean paddingChanged = bottomPadding != child.getPaddingBottom();
if (paddingChanged) {
// If we've changed the padding, then update the child and make sure a layout is requested.
child.setPadding(child.getPaddingLeft(),
child.getPaddingTop(),
child.getPaddingRight(),
bottomPadding);
child.requestLayout();
}
// Even if we didn't change the padding, if onDependentViewChanged was called then that means that the app bar
// layout was changed or was flung. In that case, we want to check for these changes over the next few animation
// frames so that we can ensure that we capture all the changes and update the view pager padding to match.
startAnimationRunnable(child, dependency);
return paddingChanged || result;
}
// Calculate the padding needed to keep the bottom of the view pager's content at the same location on the screen.
private int calculateBottomPadding(AppBarLayout dependency) {
final int totalScrollRange = dependency.getTotalScrollRange();
return totalScrollRange + dependency.getTop();
}
private void startAnimationRunnable(final View child, final View dependency) {
if (onAnimationRunnablePosted)
return;
final int onPostChildTop = child.getTop();
final int onPostDependencyTop = dependency.getTop();
onAnimationRunnablePosted = true;
// Start looking for changes at the beginning of each animation frame. If there are any changes, we have to
// ensure that layout is run again so that we can update the padding to take the changes into account.
child.postOnAnimation(new Runnable() {
private static final int MAX_COUNT_OF_FRAMES_WITH_NO_CHANGES = 5;
private int previousChildTop = onPostChildTop;
private int previousDependencyTop = onPostDependencyTop;
private int countOfFramesWithNoChanges;
#Override
public void run() {
// Make sure we request a layout at the beginning of each animation frame, until we notice a few
// frames where nothing changed.
final int currentChildTop = child.getTop();
final int currentDependencyTop = dependency.getTop();
boolean hasChanged = false;
if (currentChildTop != previousChildTop) {
previousChildTop = currentChildTop;
hasChanged = true;
countOfFramesWithNoChanges = 0;
}
if (currentDependencyTop != previousDependencyTop) {
previousDependencyTop = currentDependencyTop;
hasChanged = true;
countOfFramesWithNoChanges = 0;
}
if (!hasChanged) {
countOfFramesWithNoChanges++;
}
if (countOfFramesWithNoChanges <= MAX_COUNT_OF_FRAMES_WITH_NO_CHANGES) {
// We can still look for changes on subsequent frames.
child.requestLayout();
child.postOnAnimation(this);
} else {
// We've encountered enough frames with no changes. Do a final layout request, and don't repost.
child.requestLayout();
onAnimationRunnablePosted = false;
}
}
});
}
}
I'm not a fan of rechecking the layout on every animation frame, and this solution isn't perfect as I've seen some issues if programmatically expanding/collapsing the app bar layout, but for now I haven't found a better solution. The performance is fine on a new device and acceptable on an older device. If someone else does, please feel free to take my answer as a source and repost.

package pl.mkaras.utils;
import android.content.Context;
import android.support.design.widget.AppBarLayout;
import android.support.design.widget.CoordinatorLayout;
import android.support.v4.view.ViewCompat;
import android.support.v7.widget.Toolbar;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import java.util.List;
public class ScrollViewBehaviorFix extends AppBarLayout.ScrollingViewBehavior {
public ScrollViewBehaviorFix() {
super();
}
public ScrollViewBehaviorFix(Context context, AttributeSet attrs) {
super(context, attrs);
}
public boolean onMeasureChild(CoordinatorLayout parent, View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec,
int heightUsed) {
if (child.getLayoutParams().height == -1) {
List<View> dependencies = parent.getDependencies(child);
if (dependencies.isEmpty()) {
return false;
}
final AppBarLayout appBar = findFirstAppBarLayout(dependencies);
if (appBar != null && ViewCompat.isLaidOut(appBar)) {
int availableHeight = View.MeasureSpec.getSize(parentHeightMeasureSpec);
if (availableHeight == 0) {
availableHeight = parent.getHeight();
}
final int height = availableHeight - appBar.getMeasuredHeight();
int heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(height, View.MeasureSpec.AT_MOST);
parent.onMeasureChild(child, parentWidthMeasureSpec, widthUsed, heightMeasureSpec, heightUsed);
int childContentHeight = getContentHeight(child);
if (childContentHeight <= height) {
updateToolbar(parent, appBar, parentWidthMeasureSpec, widthUsed, parentHeightMeasureSpec, heightUsed, false);
heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(height, View.MeasureSpec.EXACTLY);
parent.onMeasureChild(child, parentWidthMeasureSpec, widthUsed, heightMeasureSpec, heightUsed);
return true;
} else {
updateToolbar(parent, appBar, parentWidthMeasureSpec, widthUsed, parentHeightMeasureSpec, heightUsed, true);
return super.onMeasureChild(parent, child, parentWidthMeasureSpec, widthUsed, parentHeightMeasureSpec, heightUsed);
}
}
}
return false;
}
private static int getContentHeight(View view) {
if (view instanceof ViewGroup) {
ViewGroup viewGroup = (ViewGroup) view;
int contentHeight = 0;
for (int index = 0; index < viewGroup.getChildCount(); ++index) {
View child = viewGroup.getChildAt(index);
contentHeight += child.getMeasuredHeight();
}
return contentHeight;
} else {
return view.getMeasuredHeight();
}
}
private static AppBarLayout findFirstAppBarLayout(List<View> views) {
int i = 0;
for (int z = views.size(); i < z; ++i) {
View view = views.get(i);
if (view instanceof AppBarLayout) {
return (AppBarLayout) view;
}
}
throw new IllegalArgumentException("Missing AppBarLayout in CoordinatorLayout dependencies");
}
private void updateToolbar(CoordinatorLayout parent, AppBarLayout appBar, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec,
int heightUsed, boolean toggle) {
toggleToolbarScroll(appBar, toggle);
appBar.forceLayout();
parent.onMeasureChild(appBar, parentWidthMeasureSpec, widthUsed, parentHeightMeasureSpec, heightUsed);
}
private void toggleToolbarScroll(AppBarLayout appBar, boolean toggle) {
for (int index = 0; index < appBar.getChildCount(); ++index) {
View child = appBar.getChildAt(index);
if (child instanceof Toolbar) {
Toolbar toolbar = (Toolbar) child;
AppBarLayout.LayoutParams params = (AppBarLayout.LayoutParams) toolbar.getLayoutParams();
int scrollFlags = params.getScrollFlags();
if (toggle) {
scrollFlags |= AppBarLayout.LayoutParams.SCROLL_FLAG_SCROLL;
} else {
scrollFlags &= ~AppBarLayout.LayoutParams.SCROLL_FLAG_SCROLL;
}
params.setScrollFlags(scrollFlags);
}
}
}
}
This behavior basically removes scroll flag SCROLL from AppBarLayout, when scrolling content in dependent view (RecyclerView, NestedScrollView) is less than view height, ie. when scrolling is not needed. It also overrides offsetting scrolling view, which is normally done by AppBarLayout.ScrollingViewBehavior. Works well when adding footer, ie. button, to scrolling view or in ViewPager, where content length may be different in each page.

I think creating a fixed header and footer could solver your problem. I would've wrote this in the comments but I don't have 50 rep. You could figure out how to do it here

I did something along the lines of ensuring I added
android:layout_gravity="end|bottom"
to the layout in XML that I wanted at the bottom of the CoordinatorLayout
and then set in code:
mRecyclerView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
#SuppressLint("NewApi")
#SuppressWarnings("deprecation")
#Override
public void onGlobalLayout() {
if (mFooterView != null) {
final int height = mFooterView.getHeight();
mRecyclerView.setPadding(0, 0, 0, height);
mRecyclerView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
}
}
});
Note: that the footer View/ViewGroup needs to be higher in the z-axis (listed below the RecyclerView in XML) to function properly

Surround your elements with a linearlayout, like that:
<android.support.design.widget.CoordinatorLayout >
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.AppBarLayout>
<android.support.v7.widget.Toolbar />
</android.support.design.widget.AppBarLayout>
<include layout="#layout/content_main" />
</LinearLayout>
</android.support.design.widget.CoordinatorLayout>

Android CoordinatorLayout Bottom Layout Behaviour Example
activity_bottom.xml
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimaryDark"
app:layout_scrollFlags="scroll|enterAlways"
app:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar" />
</android.support.design.widget.AppBarLayout>
<android.support.v7.widget.RecyclerView
android:id="#+id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#C0C0C0"
app:layout_behavior="#string/appbar_scrolling_view_behavior" />
<com.example.android.coordinatedeffort.widget.FooterBarLayout
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:layout_gravity="bottom">
<TextView
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#007432"
android:gravity="center"
android:text="Footer View"
android:textColor="#android:color/white"
android:textSize="25sp" />
</com.example.android.coordinatedeffort.widget.FooterBarLayout>
</android.support.design.widget.CoordinatorLayout>
FooterBarLayout.java
FooterBarBehavior.java

There is a library for your problem. Hope this will really help for you
Here is the library
And another problem you have mentioned fixed the footer. the below one is the relative layout so use the feature android:layout_alignParentBottom="true" on your footer.
Hope you i have solved the issue