Related
I'm having trouble implementing smooth scroll with a RecyclerView when it is paired with AppBarLayout. This is my layout:
<CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="40dp"
android:background="#ff0000"
app:layout_scrollFlags="scroll|enterAlways|snap" />
</AppBarLayout>
<RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"/>
</CoordinatorLayout>
I try to scroll to a position like so:
RecyclerView.SmoothScroller ss = new LinearSmoothScroller(getActivity()) {
#Override protected int getVerticalSnapPreference() {
return LinearSmoothScroller.SNAP_TO_END;
}
};
ss.setTargetPosition(position);
llm.startSmoothScroll(ss);
There are two problems:
If the target position is off the bottom edge of the recycler view, the scroll amount is incorrect - it is offset by the height of the AppBarLayout. If I change to SNAP_TO_START, then it works fine. Or, if I remove the AppBarLayout, it works fine in all cases.
Attempting to scroll to the last element in the recycler view is broken in additional ways. The SNAP_TO_START flag usually works fine (see #1), but in this case the recycler view refuses to scroll it up completely.
So removing the AppBarLayout fixes everything, is there some additional setting needed when using this with AppBarLayout? I'm on the latest support library version.
Thanks
Please use smoothScrollToPosition to fix your issue as below.
RecyclerView rv = (RecyclerView)findViewById(R.id.recyclerView);
rv.smoothScrollToPosition(mMessages.count-1);
the fist solution is
#Override
public int calculateDyToMakeVisible(View view, int snapPreference) {
return super.calculateDyToMakeVisible(view, snapPreference) - offset;
}
where offset may be
offset = getActionBarHeight(context);
public int getActionBarHeight(#NonNull Context context) {
final TypedArray ta = context.getTheme().obtainStyledAttributes(
new int[] {android.R.attr.actionBarSize});
int actionBarHeight = (int) ta.getDimension(0, 0);
return actionBarHeight;
}
the second solution is to replace app:layout_scrollFlags="scroll|enterAlways" with app:layout_scrollFlags="enterAlways" to prevent the actionBar from hiding
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
I have a collapsing toolbar layout that looks like this:
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/collapsing_toolbar"
android:layout_width="match_parent"
android:layout_height="#dimen/expanded_toolbar_height"
android:fitsSystemWindows="true"
app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed">
<include layout="#layout/circle_image_view"/>
<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/ThemeOverlay.AppCompat.Light" />
</android.support.design.widget.CollapsingToolbarLayout>
where circle_image_view is
<com.example.ui.CircularParseImageView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/iv_circular_backdrop"
android:layout_width="120dp"
android:layout_height="120dp"
android:layout_gravity="center"
android:fitsSystemWindows="true"
android:scaleType="centerCrop"
android:transitionName="#string/transition_pic"
app:layout_collapseMode="parallax" />
This is just a standard image view with a circular mask. When the the collapsing toolbar is expanded, the circular Image view is visible and shows like:
When collapsed, the image view is no longer visible as follows:
However it seems like the visibility of the image view is still set to Visible even in the collapsed state. When the user presses the back button, I need to determine whether the image is visible or not to perform a shared element transition animation. How can I determine if the image is currently visible or not within the collapsing toolbar?
What I have tried:
getVisibility() remains unchanged
isOpaque() remains unchanged
getImageAlpha() remains unchanged
I was able to resolve the issue by using CollapsingToolbarLayout#getContentScrim() which according to documentation:
Returns the drawable which is used for the foreground scrim.
Seems like the image view is always visible but the foreground scrim hides it so using the alpha property getContentScrim().getAlpha() you can determine whether the image is visible or not.
this can be achieved using your own implementation of a OnOffsetChangedListener.
AppBarLayout appBarLayout = (AppBarLayout) view.findViewById(R.id.app_bar_layout);
appBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
#Override
public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
if (Math.abs(verticalOffset) == appBarLayout.getTotalScrollRange()) {
// Collapsed
} else if (verticalOffset == 0) {
// Expanded
} else {
// Somewhere in between
}
}
}););
mAppBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
#Override
public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
boolean isContentHide = mCollapsingToolbarLayout.getScrimVisibleHeightTrigger() + Math.abs(verticalOffset) > mCollapsingToolbarLayout.getHeight();
}
});
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
I'm trying to do something really simple.
I would like the FAB to only appear on one tab in my TabLayout and be hidden when navigating to another tab. So for example, one tab would let you add new items in the FAB, but the next tab would not let you add items.
I have followed the 'typical' XML design layout:
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/container"
xmlns:tools="http://schemas.android.com/tools"
>
<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:minHeight="?attr/actionBarSize"
android:background="?attr/colorPrimary"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_scrollFlags="scroll|enterAlways">
<LinearLayout
android:id="#+id/search_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center_vertical"
android:orientation="horizontal">
<EditText
android:id="#+id/search_view"
android:layout_width="0dp"
android:layout_height="?attr/actionBarSize"
android:layout_weight="1"
android:background="#android:color/transparent"
android:gravity="center_vertical"
android:hint="Search"
android:imeOptions="actionSearch"
android:inputType="text"
android:maxLines="1"
android:paddingLeft="2dp"
android:singleLine="true"
android:textColor="#ffffff"
android:textColorHint="#b3ffffff" />
<ImageView
android:id="#+id/search_clear"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:src="#drawable/ic_action_cancel" />
</LinearLayout>
</android.support.v7.widget.Toolbar>
<android.support.design.widget.TabLayout
android:id="#+id/sliding_tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="?attr/colorPrimary"
app:tabMode="scrollable"
/>
</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.example.simon.behaviours.PatchedScrollingViewBehavior"/>
<android.support.design.widget.FloatingActionButton
android:id="#+id/fab"
app:borderWidth="0dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/ic_action_new"
android:layout_margin="16dp"
android:layout_gravity="bottom|right"
app:layout_anchor="#+id/viewPager"
app:layout_anchorGravity="bottom|right|end"
app:layout_behavior="com.example.simon.behaviours.ScrollingFABBehavior"
android:visibility="gone"
app:fabSize="normal">
</android.support.design.widget.FloatingActionButton>
</android.support.design.widget.CoordinatorLayout>
I have used the following behavior for the FAB. This results in any upscrolls to cause the FAB to disappear and will return back on screen on a downscroll:
public class ScrollingFABBehavior extends FloatingActionButton.Behavior {
private int toolbarHeight;
public ScrollingFABBehavior(Context context, AttributeSet attrs) {
super();
this.toolbarHeight = getToolbarHeight(context);
}
#Override
public boolean layoutDependsOn(CoordinatorLayout parent, FloatingActionButton fab, View dependency) {
return super.layoutDependsOn(parent, fab, dependency) || (dependency instanceof AppBarLayout);
}
#Override
public boolean onDependentViewChanged(CoordinatorLayout parent, FloatingActionButton fab, View dependency) {
boolean returnValue = super.onDependentViewChanged(parent, fab, dependency);
if (dependency instanceof AppBarLayout) {
CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams) fab.getLayoutParams();
int fabBottomMargin = lp.bottomMargin;
int distanceToScroll = fab.getHeight() + fabBottomMargin;
float ratio = (float)dependency.getY()/(float)toolbarHeight;
fab.setTranslationY(-distanceToScroll * ratio);
}
return returnValue;
}
public static int getToolbarHeight(Context context) {
final TypedArray styledAttributes = context.getTheme().obtainStyledAttributes(
new int[]{R.attr.actionBarSize});
int toolbarHeight = (int) styledAttributes.getDimension(0, 0);
styledAttributes.recycle();
return toolbarHeight;
}
}
I have added a viewpager addOnPageChangeListener:
viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
if (position == 0) {
FloatingActionButton floatingActionButton = (FloatingActionButton) findViewById(R.id.fab);
floatingActionButton.setVisibility(View.VISIBLE);
}
else
{
FloatingActionButton floatingActionButton = (FloatingActionButton) findViewById(R.id.fab);
floatingActionButton.setVisibility(View.GONE);
}
}
#Override
public void onPageScrollStateChanged(int state) {
}
});
I only want the FAB to appear on the first page and disappear on all the other pages.
The code works but when I swipe down on the next page, the FAB appears after even though the visibility is set to gone. I think it has something to do with the behavior set for the FAB. Does anyone know why the FAB still become visible on a swipe down if the visibility is set to gone?
This didn't end up being something I want to implement in my app but I did manage to find an answer in the end, with some help by looking through how they implemented the same thing on the wordpress app.
In the wordpress app, we see a floating action button on the first page of the app which disappears if you swipe to any of the other pages on the viewpager:
They did this through the following code - this is the code for the Activity that holds the viewpager. You can see the relevant part of the code under the onPageScrolled method which contains the eventbus that posts an event each time the page is scrolled. The event only contains one variable called positionOffset which is an integer value from 0 to 1. If you scroll and the page is half way between the two viewpagers, the positionOffset is 0.5, you get the idea:
WPMainActivity.java
mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
AppPrefs.setMainTabIndex(position);
switch (position) {
case WPMainTabAdapter.TAB_NOTIFS:
new UpdateLastSeenTask().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
break;
}
trackLastVisibleTab(position);
}
#Override
public void onPageScrollStateChanged(int state) {
// noop
}
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
// fire event if the "My Site" page is being scrolled so the fragment can
// animate its fab to match
if (position == WPMainTabAdapter.TAB_MY_SITE) {
EventBus.getDefault().post(new MainViewPagerScrolled(positionOffset));
}
}
});
The event is picked up in the fragment which contains the following code. The event will fire off the translationY method which animates the FAB vertically when the page is scrolled according to how far the page is scrolled out of view as determined by the positionOffset:
MySiteFragment
/*
* animate the fab as the users scrolls the "My Site" page in the main activity's ViewPager
*/
#SuppressWarnings("unused")
public void onEventMainThread(CoreEvents.MainViewPagerScrolled event) {
mFabView.setTranslationY(mFabTargetYTranslation * event.mXOffset);
}
Finally, the layout in the my_site_fragment.xml shows you that the FAB is actually placed into the fragments xml instead of the activity xml.
<!-- this coordinator is only here due to https://code.google.com/p/android/issues/detail?id=175330 -->
<android.support.design.widget.CoordinatorLayout
android:id="#+id/coordinator"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.FloatingActionButton
android:id="#+id/fab_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="end|bottom"
android:layout_marginBottom="#dimen/fab_margin"
android:layout_marginRight="#dimen/fab_margin"
android:src="#drawable/gridicon_create_light"
app:borderWidth="0dp"
app:rippleColor="#color/fab_pressed" />
</android.support.design.widget.CoordinatorLayout>
Hey I had exactly the same issue as you.
I found two methods which worked for me.
Method 1:
Add a static flag in your MainActivity:
public static boolean fabVisible;.
I noticed you have a listener for your viewPager to detect the current fragment page, so you can add this:
public void onPageSelected(int position) {
switch (position) {
case 0:
fabVisible = true;
mFloatingActionButton.show();
break;
default:
fabVisible = false;
mFloatingActionButton.hide();
break;
}
}
And inside your custom fab behaviour, add the following code:
if (dyConsunmed > 0 && child.getVisibility() == View.VISIBLE ) {
child.hide();
} else if (dyConsunmed < 0 && child.getVisibility() != View.VISIBLE && MainActivity.fabVisible) {
child.show();
}
The point of this method is to make sure the fab should be visible before you implement the hide & show method.
Method 2:
You don't need to add any flag like "fabVisible" in your MainActivity anymore. Although this method does require you to set the viewPager as static in your MainActivity, because we need to be able to access it in our custom fab behaviour class.
In your ScrollAwareFABBehavior class, add the following code:
if (MainActivity.viewPager.getCurrentItem() == 0) {
if (dyConsunmed > 0 && child.getVisibility() == View.VISIBLE ) {
child.hide();
} else if (dyConsunmed < 0 && child.getVisibility() != View.VISIBLE) {
child.show();
}
}
The key point of this method, is only to make the show and hide method when you are inside the fragment you want (In my case it's fragment one so the currenItem == 0). Of course in order to remove the fab in the second fragment, you still need to hide it within your viewPager listener.
If you still feel confused about the implement, feel free to check my repository on GitHub and play with the code. The address is: https://github.com/Anthonyeef/FanfouDaily
Though the feed content is all in Chinese, the code is all in English.
Implement ViewPager.onPageListener and over ride onPageSelected and show or hide FAB on Tabs as per your requirements following is the sample code:
#Override
public void onPageSelected(int position) {
//FAB_PAGE is the index of the page on which you want to show FAB
if(position == FAB_PAGE)
{
fab.setVisibility(View.VISIBLE);
}
else
{
fab.setVisibility(View.GONE);
}
}
You can also use fab.show(); and fab.hide();
Also check this for further details.
You can do it programmatically when you swipe to the next tab.
FloatingActionButton fab = (FloatingActionButton) view.findViewByID(R.id.fab)
fab.setVisibility(View.GONE);
And then set the visiblity to View.VISIBLE when you swipe back.
Create a static boolean in your activity (see YourActivity.isFABinCurrentTabVisible below) and alter it from your ViewPager, accordingly if there should be a fab in the current tab or not.
Might be a dirty fix though...
And consider using fab.show() and fab.hide() instead of setVisiblity(). These perform the fade-in and fade-out animations.
public class ScrollAwareFABBehavior extends FloatingActionButton.Behavior {
public ScrollAwareFABBehavior(Context context, AttributeSet attrs) {
super();
}
#Override
public boolean onStartNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child,
final View directTargetChild, final View target, final int nestedScrollAxes) {
// Ensure we react to vertical scrolling
return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL
|| super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, nestedScrollAxes);
}
#Override
public void onNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child,
final View target, final int dxConsumed, final int dyConsumed,
final int dxUnconsumed, final int dyUnconsumed) {
super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
if (dyConsumed > 0 && child.getVisibility() == View.VISIBLE) {
// User scrolled down and the FAB is currently visible -> hide the FAB
child.hide();
} else if (dyConsumed < 0 && child.getVisibility() != View.VISIBLE && YourActivity.isFABinCurrentTabVisible) {
// User scrolled up and the FAB is currently not visible -> show the FAB
child.show();
}
}
}
It sounds like you're approaching this from the wrong angle...
So for example, one tab would let you add new items in the FAB, but the next tab would not let you add items.
Put the FAB in the Fragment of the first page instead of the hosting Fragment / Activity. That way it will automatically disappear along with the first page fragment - it will even animate alongside it. It will also be where it belongs, since it's not at all related to the other pages / tabs.
If you really need to handle the click event in your hosting Fragment / Activity, make your first page fragment call back to the hosting Fragment / Activity when that click occurs.