Android 畫個圓 淡入淡出

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 private class SimpleView extends ImageView{          int point_x;          int point_y;          int radius = 0;          public SimpleView(Context context) {              super(context);              // TODO Auto-generated constructor stub          }          @Override          public boolean onTouchEvent(MotionEvent event) {              point_x = (int) event.getX();//擷取點擊位置              point_y = (int) event.getY();              if (event.getAction() == MotionEvent.ACTION_UP) {                  upFlag = true;              }              invalidate();              return true;          };                    protected void onDraw(android.graphics.Canvas canvas) {              alpha -= 3;              canvas.drawColor(Color.BLUE);   //設定背景色              Paint paint = new Paint();              paint.setColor(Color.WHITE);        //設定畫筆顏色              paint.setAlpha(alpha);          //設定透明度              paint.setStyle(Paint.Style.FILL);              paint.setAntiAlias(true);              if (upFlag) {                  ++radius;                  if (radius > 26) {                      upFlag = false;                      radius = 0;                      alpha = 255;                  }                  if (radius == 18) {                      alpha = 100;                  }                  canvas.drawCircle(point_x, point_y, radius, paint); //畫圓                  invalidate();              }          }      } 

　　轉載至：http://blog.csdn.net/walker02/article/details/7254829