windows-phone-8 - 如何检测两个同时触摸？

Question

在 Windows Phone 8 中检测触摸利用 System.Windows.Input.Touch.FrameReported 事件，这是开发人员可用的最原始，当然也是响应最快的触摸事件。

你会像这样使用这个事件:

public MainPage()
{
    InitializeComponent();

    // setup sounds
    Ellipse1.Tag = new Uri("Sounds/GVD_snr1.wav", UriKind.Relative);
    Ellipse2.Tag = new Uri("Sounds/GVD_snr2.wav", UriKind.Relative);
    Ellipse3.Tag = new Uri("Sounds/GVD_snr3.wav", UriKind.Relative);
    Ellipse4.Tag = new Uri("Sounds/GVD_snr4.wav", UriKind.Relative);
    Ellipse5.Tag = new Uri("Sounds/GVD_snr5.wav", UriKind.Relative);
    Ellipse6.Tag = new Uri("Sounds/GVD_snr6.wav", UriKind.Relative);
    Ellipse7.Tag = new Uri("Sounds/Gong.wav", UriKind.Relative);

    // respond to touch(es)
    var _Ellipses = new[] { Ellipse1, Ellipse2, Ellipse3, Ellipse4, Ellipse5, Ellipse6, Ellipse7 };
    System.Windows.Input.Touch.FrameReported += (s, e) =>
    {
        var _Touches =
            from touch in e.GetTouchPoints(null)
            where touch.Action == System.Windows.Input.TouchAction.Down
            let ellipse = touch.TouchDevice.DirectlyOver as Ellipse
            where _Ellipses.Contains(ellipse)
            select ellipse;
        System.Diagnostics.Debug.WriteLine("{0} touch(es).", _Touches.Count());
        foreach (var ellipse in _Touches)
        {
            var _Stream = Application.GetResourceStream(ellipse.Tag as Uri).Stream;
            var _SoundEffect = Microsoft.Xna.Framework.Audio.SoundEffect.FromStream(_Stream);
            Microsoft.Xna.Framework.FrameworkDispatcher.Update();
            _SoundEffect.Play();
        }
    };
}

(用 Lumia 920 测试)

这就像一个魅力 - 只要一次只有一个触摸。当用户尝试同时触摸两个或更多点(我的意思是完全相同的时间)时，根本不会引发事件。当用户尝试几乎同时触摸两个或多个点(仅相隔一瞬间)时，将引发事件并报告两个点。

如何检测两个同时触摸？

如果您想查看 XAML，这里是 XAML:

<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">

    <Grid.Resources>
        <Style TargetType="Ellipse">
            <Setter Property="HorizontalAlignment" Value="Left" />
            <Setter Property="VerticalAlignment" Value="Top" />
        </Style>
    </Grid.Resources>

    <Ellipse x:Name="Ellipse1" Fill="Blue" Height="177" Margin="17,17,0,0" Width="177"/>
    <Ellipse x:Name="Ellipse2" Fill="#FFFFA300" Height="223" Margin="212,25,0,0" Width="223"/>
    <Ellipse x:Name="Ellipse3" Fill="#FFFF00E8" Height="97" Margin="89,207,0,0" Width="97"/>
    <Ellipse x:Name="Ellipse4" Fill="#FF00C135" Height="162" Margin="186,249,0,0" Width="162"/>
    <Ellipse x:Name="Ellipse5" Fill="#FF00AEFF" Height="272" Margin="59,416,0,-81" Width="272"/>
    <Ellipse x:Name="Ellipse6" Fill="Red" Height="97" Margin="320,395,0,0" Width="97"/>
    <Ellipse x:Name="Ellipse7" Fill="#FFF3FF00" Height="133" Margin="10,304,0,0" Width="133"/>

</Grid>

Answer 1

添加此解决了问题:

var _Timer = new DispatcherTimer { Interval = TimeSpan.FromMilliseconds(50) };
_Timer.Tick += (s, e) =>
{
    try { Microsoft.Xna.Framework.FrameworkDispatcher.Update(); }
    catch { }
};
_Timer.Start();