简书链接:阴影的实现多种方案研究
文章字数：75,阅读全文大约需要1分钟
要实现阴影，解决方法有很多，有直接当前控件携带阴影 移动自己的背景图层，或者是让父容器进行背景图层绘制阴影，

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public class CustomShadowLayerView extends View {


    public CustomShadowLayerView(Context context) {
        super(context);
    }

    public CustomShadowLayerView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public CustomShadowLayerView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    public CustomShadowLayerView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.scale(1,1);

        Paint paint = new Paint();
        paint.setColor(Color.WHITE);
        paint.setStyle(Paint.Style.FILL);
        setLayerType( LAYER_TYPE_SOFTWARE , null);
        paint.setStrokeWidth(50);

        paint.setShadowLayer(50, 30, 30, Color.RED);
        canvas.drawRect(new Rect(0,0,getWidth()-50,getHeight()-50),paint);




        super.onDraw(canvas);




      /*  paint.setShadowLayer(5, 30, 30, Color.RED);

        canvas.drawRect(new Rect(0,0,50,50),paint);*/

    }
}