Android遇到的一些小问题

public class ShadowLayout extends FrameLayout {
    private Paint paint;
    private RectF rectF;
    private int mShadowPadding;
    private int mShadowRadius;
    private int mShadowDx;
    private int mShadowDy;
    private int mShadowColor;
    private int mRoundRadius;

    public ShadowLayout(@NonNull Context context) {
        super(context);
        initPaint();
    }

    public ShadowLayout(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        initPaint();
    }

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

    private void initPaint() {
        // ViewGroup必须设置，否则不会重绘
        setWillNotDraw(false);
        // 必须使用CPU绘制，关闭硬件加速，否则不会绘制
        setLayerType(LAYER_TYPE_SOFTWARE, null);
        mShadowPadding = getContext().getResources().getDimensionPixelSize(R.dimen.20dp);
        setPadding(mShadowPadding, mShadowPadding, mShadowPadding, mShadowPadding);
        //  圆角的弧度 
        mRoundRadius = getContext().getResources().getDimensionPixelSize(R.dimen.25dp);
        mShadowRadius = getContext().getResources().getDimensionPixelSize(R.dimen.10dp);
        // 阴影的倾斜度
        mShadowDx = getContext().getResources().getDimensionPixelSize(R.dimen.2dp);
        mShadowDy = getContext().getResources().getDimensionPixelSize(R.dimen.5dp);
        // 阴影的颜色必须带透明度，否则不会绘制
        mShadowColor = Color.parse("#9FFF0000");
        paint = new Paint();
        paint.setColor(Color.TRANSPARENT);
        paint.setShadowLayer(mShadowRadius, mShadowDx, mShadowDy, mShadowColor);
        rectF = new RectF();
    }

    public void setShadowColor(int color) {
        mShadowColor = color;
        setShadowLayer();
    }

    private void setShadowLayer() {
        paint.setShadowLayer(mShadowRadius, mShadowDx, mShadowDy, mShadowColor);
        postInvalidate();
    }


    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        rectF.left = getPaddingLeft();
        rectF.right = getWidth() - getPaddingRight();
        rectF.bottom = getHeight() - getPaddingBottom();
        rectF.top = getPaddingTop();
        // 绘制带阴影的圆角矩形
        canvas.drawRoundRect(rectF, mRoundRadius, mRoundRadius, paint);
    }
}