android自定義view小圓球指哪跑哪

  private int cx = 100;
    private int cy = 100;
    /**
     * Canvas canvas畫布.....paint畫筆
     * @param canvas
     */
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        //中心點x座標,y座標,半徑,畫筆
        Paint paint = new Paint();
        paint.setColor(Color.RED);//設置顏色

        paint.setStrokeWidth(2);//描邊的寬度2個像素
        //Paint.Style.FILL填充,,Paint.Style.STROKE描邊 ,,Paint.Style.FILL_AND_STROKE填充並且描邊
        paint.setStyle(Paint.Style.FILL);
        paint.setAntiAlias(true);//設置抗鋸齒

        canvas.drawCircle(cx,cy,100,paint);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                cx = (int) event.getX();
                cy = (int) event.getY();

                break;
            case MotionEvent.ACTION_MOVE:
                cx = (int) event.getX();
                cy = (int) event.getY();
                break;
            case MotionEvent.ACTION_UP:
                cx = (int) event.getX();
                cy = (int) event.getY();
                break;
        }

        //重新繪製....自動去調用onDraw
        postInvalidate();//.........可以使用在子線程
        //invalidate();//...只能用在主線程

        return true;
    }