Develop Reference

How to use Behavior for nested classes?

I am making behavior to hide view when AppToolBar hides. This one works if I place Cardview with behavior in same xml where CoordinatorLayout is defined. However I need that behviour deeper in hierarchy and whe I use it in Fragments it does not work any more.
public class BottomBehaviour extends CoordinatorLayout.Behavior<CardView> {
int totalHeigh;
float dencity;
int statusBarHeigh;
public BottomBehaviour() {
}
public BottomBehaviour(Context context, AttributeSet attrs) {
super(context, attrs);
dencity=context.getResources().getDisplayMetrics().density;
int height = context.getResources().getDisplayMetrics().heightPixels;
statusBarHeigh = getStatusBarHeight(context);
totalHeigh=height;
//totalHeigh = (int) (context.getResources().getDisplayMetrics().heightPixels - (56 * dencity));
Log.e("mcheck", "BottomBehaviour: ");
}
public int getStatusBarHeight(Context context) {
int result = 0;
int resourceId = context.getResources().getIdentifier("status_bar_height", "dimen", "android");
if (resourceId > 0) {
result = context.getResources().getDimensionPixelSize(resourceId);
}
return result;
}
#Override
public boolean layoutDependsOn(CoordinatorLayout parent, CardView child, View dependency) {
return dependency instanceof AppBarLayout;
}
#Override
public boolean onDependentViewChanged(CoordinatorLayout parent, CardView child, View dependency) {
int top = (int)(totalHeigh-child.getHeight()-(dependency.getY()));
child.setTranslationY(top);
Log.e("mcheck", "onDependentViewChanged: "+(dependency.getY()-statusBarHeigh)+" height "+dependency.getHeight()/dencity);
return super.onDependentViewChanged(parent, child, dependency);
}
}
Some fragment xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/tools"
android:orientation="vertical">
<android.support.v7.widget.RecyclerView
android:id="#+id/list"
android:layout_width="match_parent"
android:layout_height="0dip"
android:layout_weight="1" />
<android.support.v7.widget.CardView
android:layout_width="match_parent"
android:layout_height="56dip"
app:layout_behavior="ua.miui.forum.widget.BottomBehaviour"
card_view:cardCornerRadius="0dip"
card_view:cardElevation="8dip">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
</LinearLayout>
</android.support.v7.widget.CardView>
</LinearLayout>

CoordinatorLayout.Behaviors work only if the target view, i.e the view that holds app:layout_behavior="ua.miui.forum.widget.BottomBehaviour" is direct descendant of CoordinatorLayout. Otherwise it will not receive the nested scroll events.
If your LinearLayout is direct child of CoordinatorLayout, add the behavior to it, and then you should probably tweak you to look (for view id e.g) for yourCardView and act on nested scrolling.

How do I make a Scrollable TextView inside CollapsingToolbar?

I am currently experimenting with CoordinatorLayout + AppbarLayout + CollapsingToolbarLayout in a way such that:
1) Scroll down the Appbar using "Toolbar" [ No Nested ScrollView / RecyclerView ].
2) The content below the appbar should move along with the appbar scrolling.
3) Multiple images kept under ViewPager.
4) The last item in the ViewPager would be an textview.
I have achieved 1) and 2) using the following 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"
xmlns:tools="http://schemas.android.com/tools">
<android.support.design.widget.AppBarLayout
android:id="#+id/flexible.example.appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
>
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/flexible.example.collapsing"
android:layout_width="match_parent"
android:layout_height="300dp"
app:expandedTitleMarginBottom="94dp"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap"
app:contentScrim="?colorPrimary"
>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:id="#+id/text_sample"
android:scrollbars="vertical"
android:scrollIndicators="right"
app:layout_collapseMode="parallax"
app:layout_scrollFlags="scroll|enterAlways"
android:layout_gravity="center"
android:nestedScrollingEnabled="true"
/>
</android.support.design.widget.CollapsingToolbarLayout>
<android.support.v7.widget.Toolbar
android:id="#+id/ioexample.toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#color/PM01"
android:elevation="4dp"
app:layout_collapseMode="pin"
app:layout_anchor="#id/flexible.example.collapsing"
app:layout_anchorGravity="bottom"
app:theme="#style/ThemeOverlay.AppCompat.Light"
style="#style/ToolBarWithNavigationBack"
app:layout_scrollFlags="scroll|enterAlways|snap"
>
</android.support.v7.widget.Toolbar>
</android.support.design.widget.AppBarLayout>
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/recyclerviewcontainer"
app:layout_behavior="#string/appbar_scrolling_view_behavior" />
</android.support.design.widget.CoordinatorLayout>
What I am trying to achieve now is to make the textview inside collpasingtoolbarlayout is to be scrollable (#4 above). Since my search till now has made me believe that the Appbar is handling all the touch events by itself, this doesn't seems to be easy. But since it is a requirement, I would be more than happy to have a guidance / pointers to help me complete this.
Can someone please let me know what and where to look for achieving this functionality.

After a lot of research and some more searching through SO, I got an idea what I need to do in order to achieve the desired effect:
1) Implement a custom behavior for appbarlayout :
public class AppBarLayoutCustomBehavior extends AppBarLayout.Behavior {
private boolean setIntercept = false;
private boolean lockAppBar = false;
DragCallback mDragCallback = new DragCallback() {
#Override
public boolean canDrag(#NonNull AppBarLayout appBarLayout) {
return !lockAppBar;
}
};
#Override
public boolean onInterceptTouchEvent(CoordinatorLayout parent, AppBarLayout child, MotionEvent ev) {
super.onInterceptTouchEvent(parent, child, ev);
return setIntercept;
}
public void setInterceptTouchEvent(boolean set) {
setIntercept = set;
}
public AppBarLayoutCustomBehavior() {
super();
setDragCallback(mDragCallback);
}
public AppBarLayoutCustomBehavior(Context ctx, AttributeSet attributeSet) {
super(ctx, attributeSet);
setDragCallback(mDragCallback);
}
public void lockAppBar() {
lockAppBar = true;
}
public void unlockAppBar() {
lockAppBar = false;
}
}
2) Use this custom behavior with app bar :
CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams)appBarLayout.getLayoutParams();
final AppBarLayoutCustomBehavior mBehavior = new AppBarLayoutCustomBehavior();
lp.setBehavior(mBehavior);
/// use toolbar to enable/disable dragging on the appbar behavior. This way
/// out toolbar acts as a drag handle for the app bar.
Toolbar toolbar = (Toolbar) activity.findViewById(R.id.main_toolbar);
toolbar.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
switch(event.getAction()) {
case MotionEvent.ACTION_DOWN:
mBehavior.setInterceptTouchEvent(true);
return true;
case MotionEvent.ACTION_CANCEL:
mBehavior.setInterceptTouchEvent(false);
return true;
}
return false;
}
});
3) Set movement method on the textview to make it scrollable
textView.setMovementMethod(ScrollingMovementMethod.getInstance());

Using a view with enterAlways scrollFlag and another view with exitUntilCollapsed scrollFlag in an AppBarLayout

I'm trying to build a following layout using CoordinatorLayout and AppBarLayout:
|View 1 (Header)|
|View 2 ------------|
|RecyclerView--- |
The behavior I want to achieve is as the following:
When I scroll the RecyclerView, View 1 will completely collapse.
As I continue scrolling, View 2 will collapse until it's "collapsed" state.
RecyclerView should start scroll once View 2 is collapsed.
When I scroll back up the RecyclerView from the middle, View 1 should enter back right away while View 2 is left as its collapsed state.
Once the RecyclerView reaches the top, it should expand View 2.
This is the testing layout I created as a proof of concept.
<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_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/view1"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:text="TEST TITLE"
android:textSize="50sp"
app:layout_scrollFlags="scroll|enterAlways|snap" />
<TextView
android:id="#+id/view2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="TEST TEST TEST TEST TEST TEST TEST TEST"
android:textSize="70sp"
android:minHeight="50dp"
app:layout_scrollFlags="scroll|exitUntilCollapsed" />
</android.support.design.widget.AppBarLayout>
<android.support.v7.widget.RecyclerView
android:id="#+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior" />
</android:support.design.widget.CoordinatorLayout>
I created a test adapter to add few TextView items in RV (nothing fancy here). When I run the code, It does not actually work as expected.
Initial Screen
As I scroll down, I confirmed that View 1 is completely collapsed.
Scroll down more. View 2 collapses until it reaches minHeight. RV started scrolling after that. This is working as expected so far.
Here comes the problem. When I scroll up the RV. View 2 is expanded by the height of View 1. I'd like to see View 1 appear again.
I looked into the AppBarLayout implementation and the issue seems to be because the AppBarLayout calculates the scroll range of the whole view based on the scrollFlags, and offsetting the whole view based on the scroll offset, rather than updating each child View.
Does anyone know if there's any workaround or open source lib to resolve this issue? It doesn't have to be CoordinatorLayout/AppBarLayout approach, but I need to produce the behavior.
Thank you in advance.

Okay, I found a solution by myself, and decided to post my solution for people with similar problems.
The solution was to create a NestedCoordinatorLayout that extends CoordinatorLayout by implementing NestedScollingChild so that we can interact between two AppBarLayouts. I referenced NestedScrollView source code and the answer in this post, https://stackoverflow.com/a/36881816/6272520, but I had to make few changes to make it work the way I want to.
Here's the code for the NestedCoordinatorLayout.
public class NestedCoordinatorLayout extends CoordinatorLayout implements NestedScrollingChild {
private final NestedScrollingChildHelper scrollingChildHelper;
private final int[] parentOffsetInWindow = new int[2];
private final int[] parentScrollConsumed = new int[2];
public NestedCoordinatorLayout(Context context) {
this(context, null);
}
public NestedCoordinatorLayout(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public NestedCoordinatorLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
scrollingChildHelper = new NestedScrollingChildHelper(this);
setNestedScrollingEnabled(true);
}
//NestedScrollingChild
#Override
public void setNestedScrollingEnabled(boolean enabled) {
scrollingChildHelper.setNestedScrollingEnabled(enabled);
}
#Override
public boolean isNestedScrollingEnabled() {
return scrollingChildHelper.isNestedScrollingEnabled();
}
#Override
public boolean startNestedScroll(int axes) {
return scrollingChildHelper.startNestedScroll(axes);
}
#Override
public void stopNestedScroll() {
scrollingChildHelper.stopNestedScroll();
}
#Override
public boolean hasNestedScrollingParent() {
return scrollingChildHelper.hasNestedScrollingParent();
}
#Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,
int dyUnconsumed, int[] offsetInWindow) {
return scrollingChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow);
}
#Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
return scrollingChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
}
#Override
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
return scrollingChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
}
#Override
public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
return scrollingChildHelper.dispatchNestedPreFling(velocityX, velocityY);
}
//NestedScrollingParent
#Override
public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
scrollingChildHelper.startNestedScroll(nestedScrollAxes);
return super.onStartNestedScroll(child, target, nestedScrollAxes);
}
#Override
public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
final int[] parentConsumed = parentScrollConsumed;
//This is where the most important change happens.
//During the prescroll, we want to decrease dx/dy.
//This will make sure the top bar gets the scroll event first.
if (dispatchNestedPreScroll(dx, dy, parentConsumed, null)) {
dx -= parentConsumed[0];
dy -= parentConsumed[1];
consumed[0] += parentConsumed[0];
consumed[1] += parentConsumed[1];
}
super.onNestedPreScroll(target, dx, dy, consumed);
}
#Override
public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, parentOffsetInWindow);
super.onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
}
#Override
public void onStopNestedScroll(View target) {
scrollingChildHelper.onStopNestedScroll(target);
super.onStopNestedScroll(target);
}
#Override
public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {
scrollingChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
return super.onNestedFling(target, velocityX, velocityY, consumed);
}
#Override
public boolean onNestedPreFling(View target, float velocityX, float velocityY) {
scrollingChildHelper.dispatchNestedPreFling(velocityX, velocityY);
return super.onNestedPreFling(target, velocityX, velocityY);
}
#Override
public void onNestedScrollAccepted(View child, View target, int axes) {
super.onNestedScrollAccepted(child, target, axes);
startNestedScroll(axes & ViewCompat.SCROLL_AXIS_VERTICAL);
}
}
And the updated xml file looks like this:
<?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/app_bar_layout_for_view1"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/view1"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:text="TEST TITLE"
android:background="#android:color/white"
android:textSize="50sp"
app:layout_scrollFlags="scroll|enterAlways|snap" />
</android.support.design.widget.AppBarLayout>
<!-- Consider this like a NestedScrollView.
You need to have a scrolling behavior -->
<NestedCoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar_layout_for_view2"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/view2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:minHeight="50dp"
android:text="TEST TEST TEST TEST TEST TEST TEST TEST"
android:textSize="70sp"
app:layout_scrollFlags="scroll|exitUntilCollapsed" />
</android.support.design.widget.AppBarLayout>
<android.support.v7.widget.RecyclerView
android:id="#+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior" />
</NestedCoordinatorLayout>
</android.support.design.widget.CoordinatorLayout>
And it works like a charm

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