WPF 是否有触摸并按住手势？

Question

WPF 是否有长按手势？我找不到那个事件，所以我尝试为自己实现一个。我知道有 Stylus 类，但在 WPF 中它对我没有帮助。如果没有，那就是我的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Timers;
namespace WebControlTouch
{
    /// <summary>
    /// Due to lack of Touch-and-Hold gesture, here is implementation of it. Stupid M$.
    /// </summary>
    public static class Touch_and_Hold
    {
        #region Constructor + methods
        /// <summary>
        /// Static constructor which creates timer object with 1000ms interval, also sets parameters of Timer.
        /// </summary>
        static Touch_and_Hold()
        {
            gestureTimer = new Timer(1000);
            gestureTimer.AutoReset = false;
            gestureTimer.Elapsed += gestureTimer_Elapsed;
        }
        /// <summary>
        /// On elasped (time ofc)
        /// </summary>
        /// <seealso cref="gestureTimer"/>        
        static void gestureTimer_Elapsed(object sender, ElapsedEventArgs e)
        {
            occured = true;
        }
        /// <summary>
        /// Call it on OnTouchDown event.
        /// It will start timer and will count time of touch
        /// </summary>
        /// <returns>Returns that gesture occured</returns>
        public static void onTouch()
        {
            gestureTimer.Start();
        }

        /// <summary>
        /// Call it on touch up mainwindow event (or somewhere else)
        /// It stops gesture timer
        /// </summary>
        public static void onTouchUp()
        {
        occured = false;
        }
        #endregion 
        #region Members + properties
        /// <summary>
        /// Timer for measuring touchTime
        /// </summary>
        private static Timer gestureTimer;
        /// <summary>
        /// Do tap-and-hold occured
        /// </summary>
        private static bool occured = false;
        /// <summary>
        /// Property for getting occured flag
        /// </summary>
        public static bool occuredGesture
        {
            get { return occured; }
        }
        #endregion
    }

}

如果是，请告诉我活动名称。如果不是 - 尝试引导我解决问题。 任何帮助将不胜感激。

Answer 1

有可能以等待的方式做到这一点。创建具有特定间隔的计时器。当用户点击时启动它，并在计时器经过时返回该方法。如果用户松开手，则返回带有 false 标志的方法。

public static Task<bool> TouchHold(this FrameworkElement element, TimeSpan duration)
{
    DispatcherTimer timer = new DispatcherTimer();
    TaskCompletionSource<bool> task = new TaskCompletionSource<bool>();
    timer.Interval = duration;

    MouseButtonEventHandler touchUpHandler = delegate
    {
        timer.Stop();
        if (task.Task.Status == TaskStatus.Running)
        {
            task.SetResult(false);
        }
    };

    element.PreviewMouseUp += touchUpHandler;

    timer.Tick += delegate
    {
        element.PreviewMouseUp -= touchUpHandler;
        timer.Stop();
        task.SetResult(true);
    };

    timer.Start();
    return task.Task;
}

欲了解更多信息，请阅读此post。

Answer 2

我之前通过创建一个自定义控件来实现这一点，该控件扩展按钮以在按住延迟后延迟按钮命令的触发。

public class DelayedActionCommandButton : Button

第一个依赖属性：

public static readonly DependencyProperty DelayElapsedProperty =
        DependencyProperty.Register("DelayElapsed", typeof(double), typeof(DelayedActionCommandButton), new PropertyMetadata(0d));

public static readonly DependencyProperty DelayMillisecondsProperty =
        DependencyProperty.Register("DelayMilliseconds", typeof(int), typeof(DelayedActionCommandButton), new PropertyMetadata(1000));

public double DelayElapsed
    {
        get { return (double)this.GetValue(DelayElapsedProperty); }
        set { this.SetValue(DelayElapsedProperty, value); }
    }

    public int DelayMilliseconds
    {
        get { return (int)this.GetValue(DelayMillisecondsProperty); }
        set { this.SetValue(DelayMillisecondsProperty, value); }
    }

这些让我们可以控制延迟应该如何以及剩余多长时间的输出。

接下来我创建一个动画，以控制完成后触发命令的经过量。还有一种取消延迟的方法：

    private void BeginDelay()
    {
        this._animation = new DoubleAnimationUsingKeyFrames() { FillBehavior = FillBehavior.Stop };
        this._animation.KeyFrames.Add(new EasingDoubleKeyFrame(0, KeyTime.FromTimeSpan(TimeSpan.FromMilliseconds(0)), new CubicEase() { EasingMode = EasingMode.EaseIn }));
        this._animation.KeyFrames.Add(new EasingDoubleKeyFrame(1, KeyTime.FromTimeSpan(TimeSpan.FromMilliseconds(this.DelayMilliseconds)), new CubicEase() { EasingMode = EasingMode.EaseIn }));
        this._animation.Completed += (o, e) =>
        {
            this.DelayElapsed = 0d;
            this.Command.Execute(this.CommandParameter);    // Replace with whatever action you want to perform
        };

        this.BeginAnimation(DelayElapsedProperty, this._animation);
    }

    private void CancelDelay()
    {
        // Cancel animation
        this.BeginAnimation(DelayElapsedProperty, null);
    }

最后，我们连接事件处理程序：

private void DelayedActionCommandButton_TouchDown(object sender, System.Windows.Input.TouchEventArgs e)
    {
        this.BeginDelay();
    }

    private void DelayedActionCommandButton_TouchUp(object sender, System.Windows.Input.TouchEventArgs e)
    {
        this.CancelDelay();
    }

在 XAML 中使用时，您可以选择创建一个模板，该模板可以根据 DelayElapsed 的值进行动画处理，以提供倒计时或视觉提示（如扩展边框），随心所欲。