Using Android Property Animation to implement the animation of leaves falling.
compile 'com.waynell.library:drop-animation-view:1.0'
First, add following code into your layout xml
<com.waynell.library.DropAnimationView
    android:id="@+id/drop_animation_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:minSize="30dp"
    app:maxSize="50dp"
    app:largePercent="80%"
    app:rate="100"
    app:xAnimate="true"
    app:yAnimate="true"
    app:rotationAnimate="true"/>
Second, find this view and set drawables id
DropAnimationView view = (DropAnimationView) findViewById(R.id.drop_animation_view);
view.setDrawables(R.drawable.leaf_1,
        R.drawable.leaf_2,
        R.drawable.leaf_3,
        R.drawable.leaf_4,
        R.drawable.leaf_5,
        R.drawable.leaf_6);
finally, call startAnimation() begin doing animation.
