Android在自定义视图上绘制只有一条曲线的矩形

public class CustomView extends View {
    private Paint paint;

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

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

    private void init() {
        paint = new Paint();
        paint.setColor(Color.BLACK);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(5);
    }

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

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

        // 计算矩形的坐标
        int left = width / 4;
        int top = height / 4;
        int right = width * 3 / 4;
        int bottom = height * 3 / 4;

        // 绘制矩形
        canvas.drawRect(left, top, right, bottom, paint);
    }
}

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