how to make an object move in circular path?

问题

consider two circles with (0,0) as center and 110 and 210 as radius respectively...

i.e i have CENTER as (0,0) and CIRCLE 1 radius as 110 and CIRCLE 2 radius as 210. Now i need to move an object tball in between these two circles.

Here is my code--

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);
        }
    }

回答1:

Circle coordinates are

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

where (MX,MY) is the center or midpoint of the circle and R the radius. For screen coordinates it is sometimes better to use

Y = MY - R * sin( angle )

to get the angle consistent with mathematical conventions on circle orientation.

来源：https://stackoverflow.com/questions/24242243/how-to-make-an-object-move-in-circular-path