RecyclerView中的淡入淡出边缘

public class FadeOutEdgeDecoration extends RecyclerView.ItemDecoration {
    private final Paint paint = new Paint();
    private final int fadeLength;

    public FadeOutEdgeDecoration(int fadeLength) {
        this.fadeLength = fadeLength;
        paint.setShader(new LinearGradient(0, 0, 0, fadeLength, Color.TRANSPARENT, Color.BLACK, Shader.TileMode.CLAMP));
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);
            int bottom = child.getBottom();
            int offset = Math.min(0, parent.getHeight() - bottom);
            c.save();
            c.clipRect(child.getLeft(), child.getTop(), child.getRight(), bottom + offset);
            c.drawRect(child.getLeft(), child.getTop(), child.getRight(), bottom + offset, paint);
            c.restore();
        }
    }
}

recyclerView.addItemDecoration(new FadeOutEdgeDecoration(200));