onFling以及FlingSupport

boolean com.citrix.client.gui.ReceiverView.onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)

/**
 * Gesture detector callback
 */
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
    boolean bResult = false;
    // 滾動模式
    if (m_bScrollMode && !m_bIslockScreen) {
        // 鎖屏模式
    } else if (m_bScrollMode && m_bIslockScreen) {
    }
    // 平移模式
    else {
        m_motionEventListener.onFlingStart();
        m_flingSupport.startFling(e1, e2, velocityX, velocityY);
        float xDistance = m_flingSupport.getXPixelsSinceLastCompute();
        float yDistance = m_flingSupport.getYPixelsSinceLastCompute();
        onScrollWorker(-1 * xDistance, -1 * yDistance);
        bResult = true;
    }
    return bResult;
}

com.citrix.client.gui.FlingSupport

/**
 * This class is used to support flinging
 */
public class FlingSupport
{
    private boolean         m_bFlinging;        /**<Are we in a fling now?*/
    private long            m_lastComputeTime;  /**<The last time we recalculated*/
    private long            m_elapsedTime;      /**<Time that has elapsed since the last compute time*/
    private float           m_decay;
    private float           m_xVelocity;
    private float           m_yVelocity;
    private final float     INITIAL_DECAY  = 1;
    private final float     DECAY_CONSTANT = (float) 0.99;
      
    public FlingSupport()
    {
          
    }
      
    public void startFling(MotionEvent startEvent,MotionEvent moveEvent,float velocityX,float velocityY)
    {  
        m_bFlinging = true;
        m_lastComputeTime = startEvent.getEventTime();
        m_decay = INITIAL_DECAY;
        m_xVelocity = velocityX/1000;
        m_yVelocity = velocityY/1000;
    }
      
    public void logFling(long timeNowMs)
    {
        Log.i("ReceiverViewTest", "FlingSupport::m_bFlinging:"+m_bFlinging
                +",m_elapsedTime:"+m_elapsedTime
                +",m_decay:"+m_decay
                +",m_xVelocity:"+m_xVelocity
                +",m_yVelocity:"+m_yVelocity);
    }
      
    public void stopFling()
    {
        m_bFlinging = false;
    }
    /**
     * Recalculates the velocity
     */
    public void reCompute()
    {
        if(m_bFlinging)
        {
            long timeNowMs = SystemClock.uptimeMillis();    
            m_elapsedTime = timeNowMs - m_lastComputeTime;
            m_lastComputeTime = timeNowMs;
            m_decay *= DECAY_CONSTANT;
            m_xVelocity *= m_decay;
            m_yVelocity *= m_decay;
            logFling(timeNowMs);
        }
    }
    /**
     * Returns how many x pixels we've moved since the last move
     * @return
     */
    public float getXPixelsSinceLastCompute()
    {
        return getPixelsSinceLastCompute(true);
    }
      
    /**
     * Returns how many y pixels we've moved since the last move
     * @return
     */
    public float getYPixelsSinceLastCompute()
    {
        return getPixelsSinceLastCompute(false);
    } 
      
    private float getPixelsSinceLastCompute(boolean bX)
    {
        float pixels = 0;
        if(this.m_bFlinging)
        {           
            // Distance = velocity * time so we look how long it has been since the last time we recomputed
            pixels = m_elapsedTime * (bX ? m_xVelocity : m_yVelocity);
        }
        return pixels;
    }
      
    /**
     * Returns flag indicating whether fling is in progress   
     */
    boolean bFlingInProgress()
    {
        return m_bFlinging;
    }
}