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//Keep track of object velocities  
 
private class InertiaParam  
 
{  
 
    public VectorF InitialVelocity { get; set; }  
 
    public float InitialAngularVelocity { get; set; }  
 
    public float InitialExpansionVelocity { get; set; }  
 
    public System.Diagnostics.Stopwatch _stopwatch = new System.Diagnostics.Stopwatch();  
 
    public void Reset()  
 
    {  
 
        InitialVelocity = new VectorF(0, 0);  
 
        InitialAngularVelocity = 0;  
 
        InitialExpansionVelocity = 0;  
 
        _stopwatch.Reset();  
 
        _stopwatch.Start();  
 
    }  
 
    public void Stop()  
 
    {  
 
        _stopwatch.Stop();  
 
    }  
 
    //update velocities, velocity = distance/time  
 
    public void Update(ManipulationDeltaEventArgs e, float history)  
 
    {  
 
        float elappsedMS = (float)_stopwatch.ElapsedMilliseconds;  
 
        if (elappsedMS == 0)  
 
            elappsedMS = 1;  
 
        InitialVelocity = InitialVelocity * history + ((VectorF)e.TranslationDelta * (1F - history)) / elappsedMS;  
 
        InitialAngularVelocity = InitialAngularVelocity * history + (e.RotationDelta * (1F - history)) / elappsedMS;  
 
        InitialExpansionVelocity = InitialExpansionVelocity * history + (e.ExpansionDelta * (1F - history)) / elappsedMS;  
 
        _stopwatch.Reset();  
 
        _stopwatch.Start();  
 
    }  
 
} 
2.  将 OnBeforeInertia() 事件处理程序添加到 PictureTracker 类中：

//Fingers removed, start inertia  
 
void OnBeforeInertia(object sender, BeforeInertiaEventArgs e)  
 
{  
 
    //Tell the tracker manager that the user removed the fingers  
 
    _pictureTrackerManager.InInertia(this);  
 
 
    _processor.InertiaProcessor.InertiaTimerInterval = 15;  
 
    _processor.InertiaProcessor.MaxInertiaSteps = 500;  
 
    _processor.InertiaProcessor.InitialVelocity = _inertiaParam.InitialVelocity;  
 
    _processor.InertiaProcessor.DesiredDisplacement = _inertiaParam.InitialVelocity.Magnitude * 250;  
 
    _processor.InertiaProcessor.InitialAngularVelocity = _inertiaParam.InitialAngularVelocity * 20F / (float)Math.PI;  
 
    _processor.InertiaProcessor.DesiredRotation = Math.Abs(_inertiaParam.InitialAngularVelocity *   
 
    _processor.InertiaProcessor.InertiaTimerInterval * 540F / (float)Math.PI);  
 
    _processor.InertiaProcessor.InitialExpansionVelocity = _inertiaParam.InitialExpansionVelocity * 15;  
 
    _processor.InertiaProcessor.DesiredExpansion = Math.Abs(_inertiaParam.InitialExpansionVelocity * 4F);  
 
} 
3.  更改 PictureTracker 类，创建 ManipulationInertiaProcessor 并注册 OnBeforeInertia 事件：

class PictureTracker  
 
{  
 
...  
 
    //Calculate the Inertia start velocity  
 
    private readonly InertiaParam _inertiaParam = new InertiaParam();  
 
    private readonly ManipulationInertiaProcessor _processor = new ManipulationInertiaProcessor(ProcessorManipulations.ALL, Factory.CreateTimer());  
 
    public PictureTracker(PictureTrackerManager pictureTrackerManager)  
 
    {  
 
        _pictureTrackerManager = pictureTrackerManager;  
 
        //Start inertia velocity calculations  
 
        _processor.ManipulationStarted += (s, e) =>  
 
        {  
 
            _inertiaParam.Reset();  
 
        };  
 
        //All completed, inform the tracker manager that the current tracker  
 
        //can be reused  
 
        _processor.ManipulationCompleted += (s, e) =>   
 
        {   
 
            _inertiaParam.Stop();   
 
            pictureTrackerManager.Completed(this);   
 
        };  
 
        _processor.ManipulationDelta += ProcessManipulationDelta;  
 
        _processor.BeforeInertia += OnBeforeInertia;  
 
    }  
 
... 
 

public void InInertia(PictureTracker pictureTracker)  
 
{  
 
    //remove all touch id from the map  
 
    foreach (int id in 
 
        (from KeyValuePair<int, PictureTracker> entry in _pictureTrackerMap  
 
         where entry.Value == pictureTracker  
 
         select entry.Key).ToList())  
 
    {  
 
        _pictureTrackerMap.Remove(id);  
 
    }  
 
}