Using Google Design Library how to hide FAB button on Scroll down?

Question

Google have released Design library, I am using

 compile 'com.android.support:design:22.2.1' 

However I cant see any code examples of how to use this library and how to animate the FAB bar on scroll. I guess I can listen for scroll events on the ListView and then animate the button myself, but is this not baked into the API (is this not the point of this support library).

Is there examples for this ?

Answer 1

If you're using RecyclerView and you're looking for something simple, you can try this:

    recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener(){         @Override         public void onScrolled(RecyclerView recyclerView, int dx, int dy){             if (dy > 0)                 fabAddNew.hide();             else if (dy < 0)                 fabAddNew.show();         }     }); 

By replacing 0 with a constant, you can adjust the sensitivity of triggering, providing smoother experience

Answer 2

Making a component react to scroll events is most easily done with a custom CoordinatorLayout.Behavior, as they receive scroll events automatically when you override onStartNestedScroll().

An example Behavior that hides and shows the FAB on scroll found in this FABAwareScrollingViewBehavior, built on top of cheesesquare:

public class FABAwareScrollingViewBehavior     extends AppBarLayout.ScrollingViewBehavior {   public FABAwareScrollingViewBehavior(Context context, AttributeSet attrs) {     super(context, attrs);   }    @Override   public boolean layoutDependsOn(CoordinatorLayout parent,       View child, View dependency) {     return super.layoutDependsOn(parent, child, dependency) ||             dependency instanceof FloatingActionButton;   }    @Override   public boolean onStartNestedScroll(       final CoordinatorLayout coordinatorLayout, final View 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 View 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) {       // User scrolled down -> hide the FAB       List<View> dependencies = coordinatorLayout.getDependencies(child);       for (View view : dependencies) {         if (view instanceof FloatingActionButton) {           ((FloatingActionButton) view).hide();         }       }     } else if (dyConsumed < 0) {       // User scrolled up -> show the FAB       List<View> dependencies = coordinatorLayout.getDependencies(child);       for (View view : dependencies) {         if (view instanceof FloatingActionButton) {           ((FloatingActionButton) view).show();         }       }     }   } } 

Where your scrolling view would have app:layout_behavior="com.support.android.designlibdemo.FABAwareScrollingViewBehavior" instead of app:layout_behavior="@string/appbar_scrolling_view_behavior"

However you can replace hide() and show() with any action if you want. Details on how this was done can be found in this post and the follow up post for v22.2.1 and the follow up post for v25.1.0.

Note that this, like all scrolling behaviors of the Design Library, require that your view supports nested scrolling, which currently limits you to NestedScrollView, RecyclerView - ListView and ScrollView only work on API21+ devices.