使用SimpleOnGestureListener進行Android平滑旋轉

Question

我有我想旋轉的圓。我正在使用SimpleOnGestureListener來處理手勢，尤其是onScroll方法。

 @Override 
    public boolean onScroll(MotionEvent e1, MotionEvent e2, 
      float distanceX, float distanceY) { 

     float lWidth = e1.getX() - centeralPointX; 
     float lHeight = e1.getY() - centeralPointY; 
     float lRadius = FloatMath.sqrt(lWidth * lWidth + lHeight * lHeight); 

     if ((lRadius <= bigCircleRadius) && (lRadius >= smallCircleRadius)) { 

      mLastAngle = (float) (Math.atan(lHeight/lWidth) * 180/Math.PI) 
        + step/2; 

      float currWidth = e2.getX() - centeralPointX; 
      float currHeight = e2.getY() - centeralPointY; 
      mCurrentAngle = (float) (Math.atan(currHeight/currWidth) * 180/Math.PI) 
        + step/2; 

      mAngle = mLastAngle - mCurrentAngle; 
      mLastAngle = mCurrentAngle; 

      // show angles 
      TextView lastANGLE, endANGLE, ANGLE; 
      lastANGLE = (TextView) findViewById(R.id.currentAngle); 
      lastANGLE.setText("last " + mLastAngle); 
      endANGLE = (TextView) findViewById(R.id.endAngle); 
      ANGLE = (TextView) findViewById(R.id.angle); 

      endANGLE.setText("current " + mCurrentAngle); 
      ANGLE.setText("ANGLE " + mAngle); 

      rotation = (float) (-mAngle - step/2); 
      if (rotate != null && !rotate.hasEnded()) { 
       rotate.cancel(); 
       rotate.reset(); 
      } 
      rotate = RotateCircle(radius, radius); 
      words_layout.startAnimation(rotate); 
      return true; 
     } else 
      return false; 
    } 

但它無法正常工作。我希望那個圈子可以順利旋轉，但不會。 我該怎麼做？我試圖使用onFling方法，但它在運動結束後旋轉我的圓。但我需要在移動過程中旋轉它。

Answer 1

你可以嘗試重寫View.onTouchEvent(MotionEvent e)這樣的：

@Override 
public boolean onTouchEvent(MotionEvent event) { 
    switch(event.getAction()) { 
     case MotionEvent.ACTION_DOWN: 
      lastEventX = e.getX(); 
      lastEventY = e.getY(); 
      return true; 

     case MotionEvent.ACTION_MOVE: 
      // put your code to rotate here using lastEventX and lastEventY instead of e1.getX() and e1.getY() 
      return true; 
    } 
    return super.onTouchEvent(MotionEvent event); 
} 

Answer 2

不要一遍又一遍地撥打findViewByID（）每onScroll被觸發時，對於相同的3個對象。