ianhanniballake ianhanniballake - 5 months ago 291
Android Question

Overlap scrolling view with AppBarLayout

I want to implement the 'Flexible Space with overlapping content' pattern from the Material design scrolling techniques, such as in this video:
Flexible Space with overlapping content GIF

My XML layout right now looks like:

<android.support.design.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent">

<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="192dp"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

<android.support.design.widget.CollapsingToolbarLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_scrollFlags="scroll|exitUntilCollapsed">

<android.support.v7.widget.Toolbar
android:layout_height="?attr/actionBarSize"
android:layout_width="match_parent"
app:layout_collapseMode="pin"/>
</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"
app:layout_behavior="@string/appbar_scrolling_view_behavior">

<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<....>
</LinearLayout>
</android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinatorLayout>


Is there an easy way to accomplish this using the Design Library? Or do I have to build a custom CoordinatorLayout.Behavior to do this?

Answer

In fact, overlaying the scrolling view with the AppBarLayout is an included feature of the Android Design Support Library: you can use the app:behavior_overlapTop attribute on your NestedScrollView (or any View using ScrollingViewBehavior) to set the overlap amount:

<android.support.v4.widget.NestedScrollView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    app:behavior_overlapTop="64dp">

Note that app:behavior_overlapTop only works on views that have the app:layout_behavior="@string/appbar_scrolling_view_behavior" as it is the Behavior that is using the attribute (not the View or the Parent ViewGroup, as attributes usually apply to), hence the behavior_ prefix.

Or set it programmatically via setOverlayTop():

NestedScrollView scrollView = ...
CoordinatorLayout.LayoutParams params = 
    (CoordinatorLayout.LayoutParams) scrollView.getLayoutParams();
AppBarLayout.ScrollingViewBehavior behavior =
    (AppBarLayout.ScrollingViewBehavior) params.getBehavior();
behavior.setOverlayTop(128); // Note: in pixels
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