使用WPF/MVVM Light Toolkit处理窗口关闭事件

Question

我想处理窗口中的"Closing"事件(当用户点击右上角的"X"按钮时),以便最终显示确认消息或/并取消关闭.

我知道如何在代码隐藏中执行此操作:订阅窗口的"Closing"事件,然后使用"CancelEventArgs.Cancel"属性.

但我正在使用MVVM,所以我不确定这是一个好方法.

我认为好的方法是将Closing事件绑定到ViewModel中的Command.

我试过了:

    <i:Interaction.Triggers>
        <i:EventTrigger EventName="Closing">
            <cmd:EventToCommand Command="{Binding CloseCommand}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>

在我的ViewModel中使用关联的RelayCommand但它不起作用(命令的代码未执行).

Answer 1

我只想在View构造函数中关联处理程序:

MyWindow() 
{
    // Set up ViewModel, assign to DataContext etc.
    Closing += viewModel.OnWindowClosing;
}

然后将处理程序添加到ViewModel:

using System.ComponentModel;

public void OnWindowClosing(object sender, CancelEventArgs e) 
{
   // Handle closing logic, set e.Cancel as needed
}

在这种情况下,除了复杂性之外,你通过使用更复杂的模式和更多的间接(5个额外的XML加号命令模式行),你几乎没有获得任何东西.

"零代码隐藏"口头禅本身并不是目标,重点是将ViewModel与View分离.即使事件绑定在View的代码隐藏中,ViewModel也不依赖于View,关闭逻辑可以进行单元测试.

Answer 2

这段代码工作得很好:

ViewModel.cs:

public ICommand WindowClosing
{
    get
    {
        return new RelayCommand<CancelEventArgs>(
            (args) =>{
                     });
    }
}

在XAML中:

<i:Interaction.Triggers>
    <i:EventTrigger EventName="Closing">
        <command:EventToCommand Command="{Binding WindowClosing}" PassEventArgsToCommand="True" />
    </i:EventTrigger>
</i:Interaction.Triggers>

假如说

• ViewModel被分配给主容器的DataContext.
• xmlns:command="clr-namespace:GalaSoft.MvvmLight.Command;assembly=GalaSoft.MvvmLight.Extras.SL5"
• xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"

Answer 3

此选项更简单,也许适合您.在View Model构造函数中,您可以订阅主窗口关闭事件,如下所示:

Application.Current.MainWindow.Closing += new CancelEventHandler(MainWindow_Closing);

void MainWindow_Closing(object sender, CancelEventArgs e)
{
            //Your code to handle the event
}

祝一切顺利.

Answer 4

下面是根据MVVM模式,如果你不想知道在视图模型窗口(或者任何事件的)答案.

public interface IClosing
{
    /// <summary>
    /// Executes when window is closing
    /// </summary>
    /// <returns>Whether the windows should be closed by the caller</returns>
    bool OnClosing();
}

在ViewModel中添加接口和实现

public bool OnClosing()
{
    bool close = true;

    //Ask whether to save changes och cancel etc
    //close = false; //If you want to cancel close

    return close;
}

在窗口中,我添加了Closing事件.后面的代码不会破坏MVVM模式.View可以知道viewmodel!

void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
    IClosing context = DataContext as IClosing;
    if (context != null)
    {
        e.Cancel = !context.OnClosing();
    }
}

Answer 5

Geez,看起来像这里有很多代码.上面的Stas有最小努力的正确方法.这里是我的适应(使用MVVMLight但应该是识别)......哦,对PassEventArgsToCommand ="真"是绝对需要如上所示.

(感谢Laurent Bugnion http://blog.galasoft.ch/archive/2009/10/18/clean-shutdown-in-silverlight-and-wpf-applications.aspx)

   ... MainWindow Xaml
   ...
   WindowStyle="ThreeDBorderWindow" 
    WindowStartupLocation="Manual">



<i:Interaction.Triggers>
    <i:EventTrigger EventName="Closing">
        <cmd:EventToCommand Command="{Binding WindowClosingCommand}" PassEventArgsToCommand="True" />
    </i:EventTrigger>
</i:Interaction.Triggers> 

在视图模型中:

///<summary>
///  public RelayCommand<CancelEventArgs> WindowClosingCommand
///</summary>
public RelayCommand<CancelEventArgs> WindowClosingCommand { get; private set; }
 ...
 ...
 ...
        // Window Closing
        WindowClosingCommand = new RelayCommand<CancelEventArgs>((args) =>
                                                                      {
                                                                          ShutdownService.MainWindowClosing(args);
                                                                      },
                                                                      (args) => CanShutdown);

在ShutdownService中

    /// <summary>
    ///   ask the application to shutdown
    /// </summary>
    public static void MainWindowClosing(CancelEventArgs e)
    {
        e.Cancel = true;  /// CANCEL THE CLOSE - let the shutdown service decide what to do with the shutdown request
        RequestShutdown();
    }

RequestShutdown看起来类似于以下内容,但basicRequestShutdown或其命名的任何内容决定是否关闭应用程序(无论如何都会快乐地关闭窗口):

...
...
...
    /// <summary>
    ///   ask the application to shutdown
    /// </summary>
    public static void RequestShutdown()
    {

        // Unless one of the listeners aborted the shutdown, we proceed.  If they abort the shutdown, they are responsible for restarting it too.

        var shouldAbortShutdown = false;
        Logger.InfoFormat("Application starting shutdown at {0}...", DateTime.Now);
        var msg = new NotificationMessageAction<bool>(
            Notifications.ConfirmShutdown,
            shouldAbort => shouldAbortShutdown |= shouldAbort);

        // recipients should answer either true or false with msg.execute(true) etc.

        Messenger.Default.Send(msg, Notifications.ConfirmShutdown);

        if (!shouldAbortShutdown)
        {
            // This time it is for real
            Messenger.Default.Send(new NotificationMessage(Notifications.NotifyShutdown),
                                   Notifications.NotifyShutdown);
            Logger.InfoFormat("Application has shutdown at {0}", DateTime.Now);
            Application.Current.Shutdown();
        }
        else
            Logger.InfoFormat("Application shutdown aborted at {0}", DateTime.Now);
    }
    }

Answer 6

提问者应该使用STAS答案,但对于使用棱镜且没有galasoft/mvvmlight的读者,他们可能想尝试我使用的:

在窗口或用户控件顶部的定义中,定义命名空间:

xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"

就在这个定义之下:

<i:Interaction.Triggers>
        <i:EventTrigger EventName="Closing">
            <i:InvokeCommandAction Command="{Binding WindowClosing}" CommandParameter="{Binding}" />
        </i:EventTrigger>
</i:Interaction.Triggers>

viewmodel中的属性:

public ICommand WindowClosing { get; private set; }

在viewmodel构造函数中附加delegatecommand:

this.WindowClosing = new DelegateCommand<object>(this.OnWindowClosing);

最后,您希望在控件/窗口/关闭时触及您的代码:

private void OnWindowClosing(object obj)
        {
            //put code here
        }

Answer 7

我很想在 App.xaml.cs 文件中使用事件处理程序，该处理程序将允许您决定是否关闭应用程序。

例如，您可以在 App.xaml.cs 文件中包含类似以下代码的内容：

protected override void OnStartup(StartupEventArgs e)
{
    base.OnStartup(e);
    // Create the ViewModel to attach the window to
    MainWindow window = new MainWindow();
    var viewModel = new MainWindowViewModel();

    // Create the handler that will allow the window to close when the viewModel asks.
    EventHandler handler = null;
    handler = delegate
    {
        //***Code here to decide on closing the application****
        //***returns resultClose which is true if we want to close***
        if(resultClose == true)
        {
            viewModel.RequestClose -= handler;
            window.Close();
        }
    }
    viewModel.RequestClose += handler;

    window.DataContaxt = viewModel;

    window.Show();

}

然后在您的 MainWindowViewModel 代码中您可以有以下内容：

#region Fields
RelayCommand closeCommand;
#endregion

#region CloseCommand
/// <summary>
/// Returns the command that, when invoked, attempts
/// to remove this workspace from the user interface.
/// </summary>
public ICommand CloseCommand
{
    get
    {
        if (closeCommand == null)
            closeCommand = new RelayCommand(param => this.OnRequestClose());

        return closeCommand;
    }
}
#endregion // CloseCommand

#region RequestClose [event]

/// <summary>
/// Raised when this workspace should be removed from the UI.
/// </summary>
public event EventHandler RequestClose;

/// <summary>
/// If requested to close and a RequestClose delegate has been set then call it.
/// </summary>
void OnRequestClose()
{
    EventHandler handler = this.RequestClose;
    if (handler != null)
    {
        handler(this, EventArgs.Empty);
    }
}

#endregion // RequestClose [event]