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

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

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

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

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

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

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

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

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

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

CollapsingToolbarLayout arrow color

I'm using CollapsingToolbarLayout in my Activity, but I need to change color of back arrow when it is expanded, is there any way to do this?
What I have:
What I want to do:
Here is my layout, where i put "..." there is layout include with NestedScrollView in it.
<?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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="com.primebitstudio.swiper.AboutCouponActivity"
android:layout_marginTop="-1px">
<android.support.design.widget.AppBarLayout android:id="#+id/app_bar"
android:fitsSystemWindows="true"
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.design.widget.CollapsingToolbarLayout android:id="#+id/toolbar_layout"
android:fitsSystemWindows="true"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_scrollFlags="scroll|exitUntilCollapsed"
app:contentScrim="?attr/colorPrimary"
app:expandedTitleTextAppearance="#style/CollapsingToolbarLayoutExpandedTextStyle"
app:theme="#style/ThemeOverlay.AppCompat.Light"
app:popupTheme="#style/ToolBarStyle">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="-24dp">
<ImageView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:scaleType="fitCenter"
android:src="#drawable/test_image"
android:id="#+id/image"/>
</RelativeLayout>
<android.support.v7.widget.Toolbar android:id="#+id/toolbar"
android:layout_height="?attr/actionBarSize"
android:layout_width="match_parent"
app:layout_collapseMode="pin"
app:popupTheme="#style/ToolBarStyle" />
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
...
...
</android.support.design.widget.CoordinatorLayout>

Here is the example how I change my drawer and options icons color when layout is expanded and collapsed:
protected void onCreate(Bundle savedInstanceState) {
AppBarLayout appBarLayout = (AppBarLayout) findViewById(R.id.app_bar_layout);
appBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
#Override
public void onOffsetChanged(AppBarLayout appBarLayout, int offset)
{
Drawable upArrow = ResourcesCompat.getDrawable(getResources(), R.drawable.drawer_icon, null);
if (offset < -200)
{
upArrow.setColorFilter(Color.parseColor("#000000"), PorterDuff.Mode.SRC_ATOP);
getSupportActionBar().setHomeAsUpIndicator(upArrow);
Drawable drawable = ContextCompat.getDrawable(getApplicationContext(),R.drawable.option_menu_icon);
drawable.setColorFilter(Color.parseColor("#000000"), PorterDuff.Mode.SRC_ATOP);
toolbar.setOverflowIcon(drawable);
}
else
{
upArrow.setColorFilter(Color.parseColor("#ffffff"), PorterDuff.Mode.SRC_ATOP);
getSupportActionBar().setHomeAsUpIndicator(upArrow);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
Drawable drawable = ContextCompat.getDrawable(getApplicationContext(),R.drawable.option_menu_icon);
drawable.setColorFilter(Color.parseColor("#ffffff"), PorterDuff.Mode.SRC_ATOP);
toolbar.setOverflowIcon(drawable);
}
}
});

From the documentation on ActionBarDrawerToggle:
You can customize the the animated toggle by defining the drawerArrowStyle in your ActionBar theme.
The drawerArrowStyle attribute lists the following attributes that can be configured:
android.support.v7.appcompat:arrowHeadLength
The length of the arrow head when formed to make an arrow
android.support.v7.appcompat:arrowShaftLength
The length of the shaft when formed to make an arrow
android.support.v7.appcompat:barLength
The length of the bars when they are parallel to each other
android.support.v7.appcompat:color
The drawing color for the bars
android.support.v7.appcompat:drawableSize
The total size of the drawable
android.support.v7.appcompat:gapBetweenBars
The max gap between the bars when they are parallel to each other
android.support.v7.appcompat:spinBars
Whether bars should rotate or not during transition
android.support.v7.appcompat:thickness
The thickness (stroke size) for the bar paint
I reckon android.support.v7.appcompat:color is what you're after.
In order to change the colour at runtime, you have multiple options.
Option 1
Get the navigation icon from your Toolbar and apply a colour filter to it. For example, to colour the icon red, one could do something like this:
Drawable navIcon = mToolbar.getNavigationIcon();
navIcon.setColorFilter(Color.RED, PorterDuff.Mode.SRC_IN);
The advantage of this approach is that you can play around with the various PorterDuff.Mode constants to achieve different effects. This approach will also work (and keep working) if you decide to supply your own navigation icon (instead of the default hamburger-turns-arrow-and-vice-versa drawable).
Option 2
If you're only interested in colouring the default navigation icon, you can leverage the fact that the navigation icon drawable is a DrawerArrowDrawable, which has a setColor() method:
DrawerArrowDrawable navIcon = (DrawerArrowDrawable) mToolbar.getNavigationIcon();
navIcon.setColor(Color.RED);
This second approach may be easier to use if you're planning on animating the colour gradually with the help of i.e. ObjectAnimator.ofArgb(...) or ValueAnimator.ofArgb(...) (rather than just setting it).

appBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
int scrollRange = -1;
#Override
public void onOffsetChanged(final AppBarLayout appBarLayout, int verticalOffset) {
//Initialize the size of the scroll
if (scrollRange == -1) {
scrollRange = appBarLayout.getTotalScrollRange();
}
//Check if the view is collapsed
if (scrollRange + verticalOffset == 0) {
#SuppressLint("UseCompatLoadingForDrawables") final Drawable upArrow = getResources().getDrawable(R.drawable.abc_ic_ab_back_material);
upArrow.setColorFilter(getResources().getColor(R.color.black), PorterDuff.Mode.SRC_ATOP);
Objects.requireNonNull(getSupportActionBar()).setHomeAsUpIndicator(upArrow);
} else {
#SuppressLint("UseCompatLoadingForDrawables") final Drawable upArrow = getResources().getDrawable(R.drawable.abc_ic_ab_back_material);
upArrow.setColorFilter(getResources().getColor(R.color.white), PorterDuff.Mode.SRC_ATOP);
Objects.requireNonNull(getSupportActionBar()).setHomeAsUpIndicator(upArrow);
}
}
});
if you want to change the color of the back-button of the toolbar when using collapsingtoolbarlayout in android.
this is the condition when you want to show different color of back-button when appbarlayout is collapsed or when it is expanded.

Hiding Scrolling activity title in android studio

I have created a Scrolling activity.
I want to hide this activity title (Banglalink Latest Offers).
But
I want to show activity title at this stage (Banglalink Latest Offers).
Is it possible to do?
If yes, how?

A bit late but I think this might help someone looking for a solution for this, you can simply set the text color to transparent.
Just add the below style to your styles.xml:
<style name="ToolBarTheme">
<item name="android:textColor">#android:color/transparent</item>
</style>
and add the following attribute to your CollapsingToolbarLayout:
app:expandedTitleTextAppearance="#style/ToolBarTheme"

Simply add this line to CollapsingToolbarLayout in your xml file:
app:titleEnabled="false"

Your best bet it to convert to a normal activity (with a scrollview as a child), start with the actionbar hidden (using the hide() call below (put it inside onCreate()).
Then put the coloured backgroiund at top of screen inside scrollview.
Finally, you can programmatically toggle between hiding your title (and actionbar), but showing your header background (or vice versa) when needed by adding a horizontal scroll listener/observer.
The listener will toggle the actionbar and header view depending on how far the user has scrolled down.
E.g:
Add observer inside onStart():
hsv.getViewTreeObserver().addOnScrollChangedListener(
new ViewTreeObserver.OnScrollChangedListener()
{ #Override public void onScrollChanged()
{
Log.i(TAG,"scroll:"+hsv.getScrollX());}});
// todo adjust scrollx value to decide on hide or show call:
if (hsv.getScrollX() > 100)
getActionBar().show();
mHeaderLayoutView.setVisibility(View.GONE);
else
getActionBar().hide();
mHeaderLayoutView.setVisibily(View.VISIBLE)
...
Note: hsv is a HorizontalScrollView works.
Note, if your are using the support libraries (E.g. you activity class extends AppCompatActivity), the code would change to:
getSupportActionBar().hide();
Im not sure if the getScrollX is in pixels or dp (job for you to research).
Hope this helps!

<resources>
<dimen name="app_bar_height">180dp</dimen>
<dimen name="fab_margin">16dp</dimen>
<dimen name="text_margin">16dp</dimen>
<!-- Default screen margins, per the Android Design guidelines. -->
<dimen name="activity_horizontal_margin">16dp</dimen>
<dimen name="activity_vertical_margin">16dp</dimen>
<dimen name="appbar_padding_top">8dp</dimen>
</resources>
This must be your dimens.xml file. If you reduce the app_bar_height to 120dp or close... the text will be invisible. I dont know how to bring it back after collapse

This is working for me:
CollapsingToolbarLayout toolbarLayout = (CollapsingToolbarLayout)
findViewById(R.id.toolbar_layout);
toolbarLayout.setTitle(" ");

You have to remove the line android:theme="#style/AppTheme.AppBarOverlay"in your XML. Once you removed the title will go to background. So you able hide title of the activity. as an example, you can place a placeholder to hide it.
<?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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar"
android:layout_width="match_parent"
android:layout_height="220dp"
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"
app:toolbarId="#+id/toolbar">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
android:scaleType="centerCrop"
app:layout_collapseMode="pin"
app:srcCompat="#drawable/place_holder" />
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginLeft="6dp"
android:layout_marginStart="6dp"
android:layout_marginTop="8dp"
android:src="#mipmap/next"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>
<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>
<include layout="#layout/content_display_shop" />
</android.support.design.widget.CoordinatorLayout>

you can use supportActionBar and change title with "" (string null)
setSupportActionBar(findViewById(R.id.toolbar))
findViewById<CollapsingToolbarLayout>(R.id.toolbar_layout).title = title
supportActionBar!!.title=""
supportActionBar!!.setDisplayHomeAsUpEnabled(true)
or you can change in findViewById
findViewById<CollapsingToolbarLayout>(R.id.toolbar_layout).title = title

Calling this method from onCreate()
initCollapsingToolbar();
Defining the method
private void initCollapsingToolbar() {
final CollapsingToolbarLayout collapsingToolbar =
(CollapsingToolbarLayout) findViewById(R.id.toolbar_layout);
collapsingToolbar.setTitle(" ");
AppBarLayout appBarLayout = (AppBarLayout) findViewById(R.id.app_bar);
appBarLayout.setExpanded(true);
// hiding & showing the title when toolbar expanded & collapsed
appBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
boolean isShow = false;
int scrollRange = -1;
#Override
public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
if (scrollRange == -1) {
scrollRange = appBarLayout.getTotalScrollRange();
}
if (scrollRange + verticalOffset == 0) {
collapsingToolbar.setTitle("Your app title");
isShow = true;
} else if (isShow) {
collapsingToolbar.setTitle(" ");
isShow = false;
}
}
});
}

Hiding AppBarLayout and giving its space to the remaining view

I have a pretty standard layout using the new design libraries:
<AppBarLayout>
<CollapsingToolbarLayout>
<ImageView/>
<Toolbar/>
</CollapsingToolbarLayout>
</AppBarLayout>
<android.support.v4.widget.NestedScrollView/> <!-- content here -->
What I'm trying to do is to completely hide the whole AppBarLayout programmatically, to temporarily get rid of the Toolbar and its collapsing feature.
So I'm calling this:
private void disableCollapsing() {
AppBarLayout.LayoutParams p = (AppBarLayout.LayoutParams) collapsingToolbarLayout.getLayoutParams();
p.setScrollFlags(0);
collapsingToolbarLayout.setLayoutParams(p);
}
to disable the collapsing behavior (works well), and finally this:
#Override
public void hide() {
final AppBarLayout layout = (AppBarLayout) findViewById(R.id.appbar);
layout.animate().translationY(-layout.getHeight())
.setListener(new AnimatorListenerAdapter() {
#Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
layout.setVisibility(View.GONE);
}
}).start();
}
I make the AppBarLayout translate to the top (works smoothly), and at the end of the animation set is visibility to View.GONE.
Issue
At the end of the animation, no matter I also set the visibility to GONE, I can't get the space that was previously occupied by the AppBarLayout. My NestedScrollView remains confined in the lower half of the screen, as if the AppBarLayout was still there (which is not). How can I fix it?
Before hiding:
After hiding (AppBar translated to the top):
As you can see, the top space is empty and unreachable. The scroll view scrolls inside the margins it had before, as if the visibility change was not measured by the CoordinatorLayout.
I have tried calling coordinator.requestLayout(), with no success.
I also tried setting the AppBarLayout as an app:anchor for my NestedScrollView, but that screws things up - scroll view ends up taking the whole screen even before hiding.
I was thinking of a custom Behavior to be set on the scroll view when entering this hidden-AppBar mode, but I can't get started on that.

Yes this looks like a bug, I solved this issue for my application setting the appbar height to 0:
android.support.design.widget.AppBarLayout appbar = (android.support.design.widget.AppBarLayout) findViewById(R.id.appbar);
CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams)appbar.getLayoutParams();
lp.height = 0;
appbar.setLayoutParams(lp);

As mentioned above, setting the Coordinator.LayoutParams#height fixes the issue.
However, I wanted to express how/when this occurs (not necessarily why):
The CollaspingToolbarLayout will exhibit this behavior only when its app:layout_scrollFlags property is set to exitUntilCollapsed and its nested ToolBar also has defines app:layout_collapseMode="pin". With this combination of flags, the Toolbar will pin itself to the top of the screen, and this is intentional and sometimes desirable.
(snipped for brevity)
<androidx.coordinatorlayout.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">
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<com.google.android.material.appbar.CollapsingToolbarLayout
android:id="#+id/collapsingToolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_scrollFlags="scroll|exitUntilCollapsed">
<!-- some other component here, i.e ImageView -->
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:gravity="top"
app:layout_collapseMode="pin" />
</com.google.android.material.appbar.CollapsingToolbarLayout>
</com.google.android.material.appbar.AppBarLayout>
<!-- some scrolling view/layout -->
</androidx.coordinatorlayout.widget.CoordinatorLayout>
In the Fragment/Activity after the view is created, in Kotlin + ViewBinding:
binding.appbar.updateLayoutParams<CoordinatorLayout.LayoutParams> {
height = 0
}
For me, I had to capture the height of the AppBarLayout before hiding it to restore it to its original height when I wanted to show it.
private var appbarLayoutHeight = 0
private fun hideAppBar() {
appbarLayoutHeight = binding.appbar.measuredHeight
binding.appbar.updateLayoutParams<CoordinatorLayout.LayoutParams> {
height = 0
}
}
private fun showAppBar() {
binding.appbar.updateLayoutParams<CoordinatorLayout.LayoutParams> {
height = appbarLayoutHeight
}
}
Disclaimer: ViewBinding is not necessary to achieve this, nor is using Kotlin, and it's just what I use to acquire the AppBarLayoout and make this as terse/sugary as possible.

This works for me. Just toggles appbar on/off.
private boolean hide = true;
public void toggleAppBar() {
// Calculate ActionBar height
TypedValue tv = new TypedValue();
int actionBarHeight = 0;
if (getTheme().resolveAttribute(android.R.attr.actionBarSize, tv, true)) {
actionBarHeight = TypedValue.complexToDimensionPixelSize(tv.data, getResources().getDisplayMetrics());
}
CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams)appBarLayout.getLayoutParams();
lp.height = hide ? 0 : actionBarHeight;
appBarLayout.setLayoutParams(lp);
appBarLayout.setExpanded(!hide, true);
hide = !hide;
appbar_layout.xml
<?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">
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/appBarLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/AppTheme.AppBarOverlay">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="#style/AppTheme.PopupOverlay" />
</com.google.android.material.appbar.AppBarLayout>
<include layout="#layout/content_main" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>

Thanks #Caleb Kleveter that is my code for Kotlin
val appBarLayout = activity?.findViewById<AppBarLayout>(R.id.app_bar_layout)
val lp = appBarLayout?.layoutParams
lp?.height = 0;
appBarLayout?.layoutParams = lp

The following works as well
appBarLayout.setExpanded(false, false);
appBarLayout.setVisibility(View.GONE);

Android Material Design - How to change background color of Toolbar after CollapsingToolbarLayout is collapsed

After the user scrolls down the screen, the image in the CollapsingToolbarLayout disappears and is left with a toolbar with the back button, content title, and settings menu. I want to know how to change the background color of that toolbar only when its in a 'collapsed' state.
The action I am referring to is similar to this where the toolbar background color changes to green:
Below the CollapsingToolbarLayout I have a NestedScrollView with CardViews

I think you're after app:contentScrim.
<android.support.design.widget.CollapsingToolbarLayout
...
app:contentScrim="?attr/colorPrimary">
<!-- Toolbar and ImageView here -->
</android.support.design.widget.CollapsingToolbarLayout>

First remove
app:contentScrim="?attr/colorPrimary">
from CollapsingToolbarLayout
Add library
compile 'com.android.support:palette-v7:23.2.1'
And add below code in java code
Bitmap bitmap = BitmapFactory.decodeResource(getApplicationContext().getResources(), R.drawable.ny);
Palette.generateAsync(bitmap,
new Palette.PaletteAsyncListener() {
#Override
public void onGenerated(Palette palette) {
Palette.Swatch vibrant =
palette.getVibrantSwatch();
int mutedColor = palette.getVibrantSwatch().getRgb();
if (vibrant != null) {
// If we have a vibrant color
// update the title TextView
collapseToolbar.setBackgroundColor(mutedColor);
// mutedColor = palette.getMutedColor(R.attr.colorPrimary);
collapseToolbar.setStatusBarScrimColor(palette.getDarkMutedColor(mutedColor));
collapseToolbar.setContentScrimColor(palette.getMutedColor(mutedColor));
}
}
});

Just use CollapsingToolbarLayout XML attribute contentScrim to set Toolbar background color when it's in collapsed mode.
app:contentScrim="YOUR_TOOLBAR_COLOR"
Here is an Example:
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/collapsing_toolbar"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed">
<ImageView
android:id="#+id/img_group_photo"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
android:scaleType="centerCrop"
app:layout_collapseMode="parallax" />
<android.support.v7.widget.Toolbar
android:id="#+id/anim_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>
Hope this will help~

Maybe what you have been looking for is this :
myCollapsingToolbar.setContentScrimColor(getResources().getColor(R.color.my_color_id));
It worked for me and changed the color of the collapsingToolbar once it was collapsed to help me fit the main color of an image that was displayed when the collapsingToolbar was full scale. With this, the color can obviously be changed programatically!
I know I'm late, but I hope it could help.

You can use an AppBarLayout's offset listener and change the CollapsingTollbar attributes according to the desired behavior.
appBarLayout.addOnOffsetChangedListener { _, verticalOffSet ->
if (Math.abs(verticalOffSet) == appBarLayout.totalScrollRange) {
//Collapsed
toolBar.setBackgroundDrawable(ContextCompat.getDrawable(this,
R.drawable.last_revolut_gradient))
} else {
//Expanded
toolBar.setBackgroundColor(ContextCompat.getColor(this,
android.R.color.transparent))
}
}

Bitmap bitmap = BitmapFactory.decodeResource(getResources(),
R.drawable.header);
Palette.from(bitmap).generate(new Palette.PaletteAsyncListener() {
#SuppressWarnings("ResourceType")
#Override
public void onGenerated(Palette palette) {
Palette.Swatch vibrant =
palette.getVibrantSwatch();
if (vibrant != null) {
collapsingToolbar.setBackgroundColor(getResources().getColor(R.color.cpb_blue));
collapsingToolbar.setStatusBarScrimColor(getResources().getColor(R.color.cpb_blue));
collapsingToolbar.setContentScrimColor(getResources().getColor(R.color.cpb_blue));
}
}
});