How to sync scroll of two CoordinatorLayout + AppBarLayout

Question

I have an activity with XML.

Something like:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
    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:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <android.support.design.widget.CoordinatorLayout
        android:id="@+id/coordinator"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.design.widget.AppBarLayout
            android:id="@+id/appbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:background="@color/primary"
                android:theme="@style/ToolbarStyle"
                android:gravity="center_vertical"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
                app:layout_scrollFlags="scroll|enterAlways|snap"
                style="@style/bold" />

            <android.support.design.widget.TabLayout
                android:id="@+id/tabs"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:theme="@style/TabLayoutStyle"
                android:animateLayoutChanges="true"
                app:tabGravity="fill"
                app:tabMode="fixed"
                app:tabTextAppearance="@style/TabStyle"/>

        </android.support.design.widget.AppBarLayout>

        <com.wedmegood.planner.view.XViewPager
            android:id="@+id/main_container"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_gravity="fill_vertical"
            app:layout_behavior="@string/appbar_scrolling_view_behavior" />

        ...

</android.support.v4.widget.DrawerLayout>

A Fragment of the ViewPager has a CoordinatorLayout and AppBarLayout + CollapsingToolbarLayout.

Fragment's 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:id="@+id/root"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/primaryDark"
    app:layout_behavior="@string/appbar_scrolling_view_behavior">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fitsSystemWindows="true"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapse_toolbar"
            android:layout_width="match_parent"
            android:layout_height="@dimen/my_wedding_banner_height"
            android:minHeight="48dp"
            android:fitsSystemWindows="true"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed|snap">

            <RelativeLayout
                android:id="@+id/banner"
                android:layout_width="match_parent"
                android:layout_marginTop="0dp"
                android:layout_height="match_parent"
                app:layout_collapseMode="none">


            </RelativeLayout>

            <android.support.design.widget.TabLayout
                android:id="@+id/tabs"
                android:layout_width="match_parent"
                android:layout_height="48dp"
                android:layout_gravity="bottom"
                android:animateLayoutChanges="true"
                app:tabMode="fixed"
                app:tabGravity="fill"
                app:tabTextColor="@color/primary"
                app:tabSelectedTextColor="@color/primary"
                app:tabIndicatorColor="@color/accent"
                app:tabIndicatorHeight="4dp"
                app:tabTextAppearance="@style/TabStyle"/>

        </android.support.design.widget.CollapsingToolbarLayout>

    </android.support.design.widget.AppBarLayout>

        <com.wedmegood.planner.view.XViewPager
            android:id="@+id/viewpager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_behavior="@string/appbar_scrolling_view_behavior" />

</android.support.design.widget.CoordinatorLayout>

The fragment has a banner, the RelativeLayout. I want to sync scroll of these two AppBarLayouts so that the outer AppBar collapses either before/after (doesn't matter if it happens before or after) the inside AppBar collapses? I tried setting and unsetting scroll flags of 2 AppBars depending on their Offset change listener, it kinda works but doesn't give a smooth scroll effect. I can change the fragment's XML completely as long as the banner works fine.

Also, is there a way to change style / call TabLayout's setTabTextColors when CollapsingToolbarLayout collapses/expands?

Answer 1

I face the same problem days ago. Finally, I found a solution from SwipeRefreshLayout. Just extend CoordinatorLayout and implement NestedScrollingChild interface. It works!

here is my code:

public class NestedCoordinatorLayout extends CoordinatorLayout implements NestedScrollingChild {
private final NestedScrollingChildHelper mNestedScrollingChildHelper;

private final int[] mParentOffsetInWindow = new int[2];
private final int[] mParentScrollConsumed = new int[2];

public NestedCoordinatorLayout(Context context) {
    this(context, null, 0);
}

public NestedCoordinatorLayout(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public NestedCoordinatorLayout(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    mNestedScrollingChildHelper = new NestedScrollingChildHelper(this);
    setNestedScrollingEnabled(true);
}

// NestedScrollingChild

@Override
public void setNestedScrollingEnabled(boolean enabled) {
    mNestedScrollingChildHelper.setNestedScrollingEnabled(enabled);
}

@Override
public boolean isNestedScrollingEnabled() {
    return mNestedScrollingChildHelper.isNestedScrollingEnabled();
}

@Override
public boolean startNestedScroll(int axes) {
    return mNestedScrollingChildHelper.startNestedScroll(axes);
}

@Override
public void stopNestedScroll() {
    mNestedScrollingChildHelper.stopNestedScroll();
}

@Override
public boolean hasNestedScrollingParent() {
    return mNestedScrollingChildHelper.hasNestedScrollingParent();
}

@Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,
                                    int dyUnconsumed, int[] offsetInWindow) {
    return mNestedScrollingChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed,
            dxUnconsumed, dyUnconsumed, offsetInWindow);
}

@Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
    return mNestedScrollingChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
}

@Override
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
    return mNestedScrollingChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
}

@Override
public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
    return mNestedScrollingChildHelper.dispatchNestedPreFling(velocityX, velocityY);
}

@Override
public void onNestedScrollAccepted(View child, View target, int axes) {
    super.onNestedScrollAccepted(child, target, axes);

    // Dispatch up to the nested parent
    startNestedScroll(axes & ViewCompat.SCROLL_AXIS_VERTICAL);
}

@Override
public void onStopNestedScroll(View target) {
    super.onStopNestedScroll(target);
    stopNestedScroll();
}

@Override
public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
    super.onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
    dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
            mParentOffsetInWindow);
}

@Override
public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
    super.onNestedPreScroll(target, dx, dy, consumed);

    final int[] parentConsumed = mParentScrollConsumed;
    if (dispatchNestedPreScroll(dx - consumed[0], dy - consumed[1], parentConsumed, null)) {
        consumed[0] += parentConsumed[0];
        consumed[1] += parentConsumed[1];
    }
}
}

Use it in your fragment's layout (Inner coordinator layout).