android - 如何使物体沿圆形路径移动？

Question

考虑以(0,0)为圆心，分别以110和210为半径的两个圆...

即我将 CENTER 设为 (0,0)，CIRCLE 1 半径设为 110，CIRCLE 2 半径设为 210。现在我需要在这两个圆圈之间移动一个对象 tball。

这是我的代码--

public void run() {

        while (isitok == true) {
            // perform drawing
            if (!holder.getSurface().isValid()) {
                continue;
            }
            Canvas canvas = holder.lockCanvas();
            canvas.drawARGB(255, 150, 150, 10);

            // System.out.println("Canvas matrix  -" + canvas.getm));
            Paint p = new Paint();

            // canvas.drawBitmap(tball, (x - tball.getWidth()) / 2,
            // (y - tball.getHeight()) / 2, p);

            p.setStyle(Paint.Style.STROKE);
            p.setColor(Color.WHITE);
            p.setColor(Color.parseColor("#0101DF"));

            canvas.drawCircle(canvas.getWidth() / 2,
                    canvas.getHeight() / 2, 60, p);
            canvas.drawCircle(canvas.getWidth() / 2,
                    canvas.getHeight() / 2, 110, p);

            float x = (canvas.getWidth() / 2) - (tball.getWidth() / 2);
            float y = (canvas.getHeight() / 2) - 110 + (110 - 60) / 2
                    - (tball.getHeight() / 2);

            canvas.drawBitmap(tball, x, y, p);

            float movingpts[];

            holder.unlockCanvasAndPost(canvas);
        }
    }

Answer 1

圆坐标是

X = MX + R * cos( angle )
Y = MY + R * sin( angle )

其中 (MX,MY) 是圆的中心或中点，R 是半径。对于屏幕坐标，有时使用

Y = MY - R * sin( angle )

获得与圆方向数学约定一致的 Angular 。