Android -如何绘制一个透明的矩形边框形状，只有它的角是可见的？

public class TransparentRectangleView extends View {
    private Paint paint;
    private int borderColor;
    private int borderWidth;
    private int cornerSize;

    public TransparentRectangleView(Context context) {
        super(context);
        init();
    }

    public TransparentRectangleView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public TransparentRectangleView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        paint = new Paint();
        paint.setAntiAlias(true);
        borderColor = Color.RED; // 设置边框颜色
        borderWidth = 5; // 设置边框宽度
        cornerSize = 50; // 设置角的大小
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        int width = getWidth();
        int height = getHeight();

        // 绘制矩形边框
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(borderWidth);
        paint.setColor(borderColor);
        canvas.drawRect(0, 0, width, height, paint);

        // 绘制角
        paint.setStyle(Paint.Style.FILL);
        paint.setColor(borderColor);
        canvas.drawRect(0, 0, cornerSize, cornerSize, paint); // 左上角
        canvas.drawRect(width - cornerSize, 0, width, cornerSize, paint); // 右上角
        canvas.drawRect(0, height - cornerSize, cornerSize, height, paint); // 左下角
        canvas.drawRect(width - cornerSize, height - cornerSize, width, height, paint); // 右下角
    }
}

<com.example.TransparentRectangleView
    android:layout_width="match_parent"
    android:layout_height="match_parent" />