如何在Xamarin.UWP应用程序中实现LongPress？

问题描述

我正在尝试实现自定义PlatformEffect，该自定义Xamarin.UWP将在用户为我的GestureSettings按住控件很长时间时执行。但是我发现我的应用程序不响应鼠标单击。我读到我需要根据备注here更改应用程序的{{1}}来解决此问题。问题是我不知道如何为Xamarin.UWP应用程序做到这一点，任何想法都将非常有帮助。

解决方法

如何更改Xamarin.UWP应用程序的GestureSettings？

源自官方document， Touch可以产生Hold动作，但是鼠标设备通常不能产生。因此，如果要实现鼠标保持，则需要使用add {{ 1}}作为元素，并使用GestureRecognizer的holding事件来实现鼠标保持。有关更多详细信息，请参阅以下内容。

GestureRecognizer

UWPMouseEffect

public static class MouseHoldingEffect
{

    public static readonly BindableProperty MouseHoldingProperty =
    BindableProperty.CreateAttached("MouseHolding",typeof(Action),typeof(MouseHoldingEffect),default(Action),propertyChanged: OnhandlerChanged);


    public static Action GetMouseHolding(BindableObject view)
    {
        return (Action)view.GetValue(MouseHoldingProperty);
    }


    public static void SetMouseHolding(BindableObject view,Action value)
    {
        view.SetValue(MouseHoldingProperty,value);
    }

    static void OnhandlerChanged(BindableObject bindable,object oldValue,object newValue)
    {
        var view = bindable as View;
        if (view == null)
        {
            return;
        }

        Action action = (Action)newValue;
        if (action != null)
        {
            view.Effects.Add(new ControlTooltipEffect());
        }
        else
        {
            var toRemove = view.Effects.FirstOrDefault(e => e is ControlTooltipEffect);
            if (toRemove != null)
            {
                view.Effects.Remove(toRemove);
            }
        }
    }

    class ControlTooltipEffect : RoutingEffect
    {
        public ControlTooltipEffect() : base($"Microsoft.{nameof(MouseHoldingEffect)}")
        {

        }
    }
}

用法

public class UWPMouseEffect : PlatformEffect
{
    Windows.UI.Input.GestureRecognizer recognizer;
    ManipulationInputProcessor manipulationProcessor;
   
    protected override void OnAttached()
    {
        var control = Control ?? Container;

        if (control is UIElement)
        {
            var mouseHolding = Element.GetValue(MouseHoldingEffect.MouseHoldingProperty) as Action;
            var target = control as UIElement;
            var parent = Window.Current.Content;
            recognizer = new Windows.UI.Input.GestureRecognizer();
            manipulationProcessor = new ManipulationInputProcessor(recognizer,target,parent,mouseHolding);
        }
    }

    protected override void OnDetached()
    {

    }
}

class ManipulationInputProcessor
{
    Action mouseHolding;
    Windows.UI.Input.GestureRecognizer recognizer;
    UIElement element;
    UIElement reference;
    TransformGroup cumulativeTransform;
    MatrixTransform previousTransform;
    CompositeTransform deltaTransform;
    public ManipulationInputProcessor(Windows.UI.Input.GestureRecognizer gestureRecognizer,UIElement target,UIElement referenceFrame,Action holdingAction)
    {
        recognizer = gestureRecognizer;
        element = target;
        reference = referenceFrame;
        mouseHolding = holdingAction;
        // Initialize the transforms that will be used to manipulate the shape
        InitializeTransforms();

        // The GestureSettings property dictates what manipulation events the
        // Gesture Recognizer will listen to.  This will set it to a limited
        // subset of these events.
        recognizer.GestureSettings = GenerateDefaultSettings();

        // Set up pointer event handlers. These receive input events that are used by the gesture recognizer.
        element.PointerPressed += OnPointerPressed;
        element.PointerMoved += OnPointerMoved;
        element.PointerReleased += OnPointerReleased;
        element.PointerCanceled += OnPointerCanceled;


        recognizer.Holding += Recognizer_Holding;

    }

    private void OnPointerMoved(object sender,PointerRoutedEventArgs e)
    {
        recognizer.ProcessMoveEvents(e.GetIntermediatePoints(reference));
    }

    private void OnPointerCanceled(object sender,PointerRoutedEventArgs e)
    {
        recognizer.CompleteGesture();
        element.ReleasePointerCapture(e.Pointer);
    }

    private void OnPointerReleased(object sender,PointerRoutedEventArgs e)
    {
        recognizer.ProcessUpEvent(e.GetCurrentPoint(reference));

        // Release the pointer
        element.ReleasePointerCapture(e.Pointer);
    }

    private void OnPointerPressed(object sender,PointerRoutedEventArgs e)
    {
        element.CapturePointer(e.Pointer);
        // Feed the current point into the gesture recognizer as a down event
        recognizer.ProcessDownEvent(e.GetCurrentPoint(reference));
    }

    private GestureSettings GenerateDefaultSettings()
    {
        return GestureSettings.HoldWithMouse;
    }

    private void Recognizer_Holding(Windows.UI.Input.GestureRecognizer sender,HoldingEventArgs args)
    {
        System.Diagnostics.Debug.WriteLine("-----------Holding---------");
        mouseHolding();
    }

    private void InitializeTransforms()
    {
        cumulativeTransform = new TransformGroup();
        deltaTransform = new CompositeTransform();
        previousTransform = new MatrixTransform() { Matrix = Matrix.Identity };

        cumulativeTransform.Children.Add(previousTransform);
        cumulativeTransform.Children.Add(deltaTransform);

        element.RenderTransform = cumulativeTransform;
    }
}

ViewModel

<StackLayout>
    <Label
        effect:MouseHoldingEffect.MouseHolding="{Binding MouseHoldingAction}"
        FontSize="25"
        Text="Hello" VerticalOptions="Center" HorizontalOptions="Center" Margin="100"/>
</StackLayout>