如何在Silverlight中的命令之前触发行为 - 禁用双击？

Question

我试图建立一种行为，禁用该按钮并更改文本以遵循常见模式禁用按钮来停止用户双击。我需要行为更改在命令前生效。我能以这种方式使用行为吗？

视图：（设置在DataContext在后面的代码的加载事件）

<Grid x:Name="LayoutRoot" Background="White"> 
    <Button Height="50" Width="150" Content="Save" Command="{Binding ButtonClickedCommand}" IsEnabled="{Binding IsNextButtonEnabled}"> 
     <i:Interaction.Triggers> 
      <i:EventTrigger EventName="Click"> 
       <behaviors:SubmitButtonBehavior LoadingButtonText="WAIT!!!..." IsEnabled="True" IsFinished="{Binding IsFinishedSubmitButtonBehavior}" /> 
      </i:EventTrigger> 
     </i:Interaction.Triggers> 
    </Button> 
</Grid> 

视图模型

使用System.Windows; 使用GalaSoft.MvvmLight;使用GalaSoft.MvvmLight.Command的 ; 命名空间SubmitButtonBehaviorTest { 公共类MainPageViewModel：ViewModelBase {/// /// 私人isFinishedSubmitButtonBehavior财产。 ///
private bool isFinishedSubmitButtonBehavior;

public bool IsFinishedSubmitButtonBehavior 
    { 
     get 
     { 
      return this.isFinishedSubmitButtonBehavior; 
     } 

     set 
     { 
      this.isFinishedSubmitButtonBehavior = value; 
      this.RaisePropertyChanged("IsFinishedSubmitButtonBehavior"); 
     } 
    } 

    /// <summary> 
    /// Private ButtonClickedCommand property. 
    /// </summary>    
    private RelayCommand buttonClickedCommand; 

    public RelayCommand ButtonClickedCommand 
    { 
     get 
     { 
      return this.buttonClickedCommand; 
     } 

     private set 
     { 
      this.buttonClickedCommand = value; 
     } 
    } 

    public MainPageViewModel() 
    { 
     this.ButtonClickedCommand = new RelayCommand(
      () => 
      { 
       MessageBox.Show("Clicked"); 
       this.IsFinishedSubmitButtonBehavior = true; 
      }); 
    } 
} 

}

行为：使用System.Windows

namespace SubmitButtonBehaviorTest.Behaviors 

{ ; using System.Windows.Controls; using System.Windows.Interactivity;

/// <summary> 
/// Attach this behavior to disable the button on click and change the text 
/// </summary> 
public class SubmitButtonBehavior : TriggerAction<UIElement> 
{ 
    /// <summary> 
    /// The original button text, reset when the IsEnabled is set back. 
    /// </summary> 
    public string OriginalButtonText { get; set; } 

    /// <summary> 
    /// Gets or sets the loading button text. 
    /// </summary> 
    /// <value>The loading button text.</value> 
    public string LoadingButtonText { get; set; } 

    /// <summary> 
    /// Gets or sets a value indicating whether [change button text]. 
    /// </summary> 
    /// <value><c>true</c> if [change button text]; otherwise, <c>false</c>.</value> 
    public bool ChangeButtonText { get; set; } 

    /// <summary> 
    /// Set this to true when the operation is finished. 
    /// </summary> 
    /// <value> 
    ///  <c>true</c> if this instance is finished; otherwise, <c>false</c>. 
    /// </value> 
    public bool IsFinished 
    { 
     get { return (bool)GetValue(IsFinishedProperty); } 
     set 
     { 
      SetValue(IsFinishedProperty, value); 
      this.OnIsFinishedChanged(); 
     } 
    } 

    /// <summary> 
    /// Called when [is finished change]. 
    /// </summary> 
    /// <param name="value">if set to <c>true</c> [value].</param> 
    private void OnIsFinishedChanged() 
    { 
     if (this.AssociatedObject != null && !((Button)this.AssociatedObject).IsEnabled) 
     { 
      ((Button)this.AssociatedObject).IsEnabled = true; 
      ((Button)this.AssociatedObject).Content = this.OriginalButtonText; 
     } 
    } 

    // Using a DependencyProperty as the backing store for IsFinished. This enables animation, styling, binding, etc... 
    public static readonly DependencyProperty IsFinishedProperty = 
     DependencyProperty.Register("IsFinished", typeof(bool), typeof(SubmitButtonBehavior), new PropertyMetadata(false)); 

    /// <summary> 
    /// Initializes a new instance of the <see cref="SubmitButtonBehavior"/> class. 
    /// </summary> 
    public SubmitButtonBehavior() 
    { 
     // defaults 
     this.ChangeButtonText = true; 
     this.LoadingButtonText = "Please Wait..."; 
     // AssociatedObject is empty at initialization this.originalButtonText = this.AssociatedObject.Content.ToString(); 
    } 

    protected override void Invoke(object parameter) 
    { 
     if (this.IsEnabled) 
     { 
      Button clickedButton = ((Button)this.AssociatedObject); 
      clickedButton.IsEnabled = false; 
      this.OriginalButtonText = clickedButton.Content.ToString(); 
      if (this.ChangeButtonText) 
      { 
       clickedButton.Content = this.LoadingButtonText; 
      } 
     } 
    } 
} 

}

编辑：建议与禁止通过CanExecute。按钮文字仍然不会改变。此外，我仍然希望将其作为可重复使用的行为，但这也可能是一种好方法。

this.ButtonClickedCommand = new RelayCommand<Button>(
      (clickedButton) => 
      { 
       string originalText = clickedButton.Content.ToString(); 
       this.IsSubmitting = true; 
       clickedButton.Content = "Please Wait..."; 
       MessageBox.Show("Clicked"); 
       this.IsFinishedSubmitButtonBehavior = true; 
       this.IsSubmitting = false; 
       clickedButton.Content = originalText; 
      }, 
      (clickedButton) => 
      { 
       return !this.IsSubmitting; 
      } 
      ); 

编辑：我发现一个很好的解决方案，使用消息传递，并补充说，作为我自己的问题的答案。

Answer 1

我发现比使用MvvmLight工具箱消息传递的行为更好的解决方案。使用在MainPage.xaml.cs中 1.创建密钥 2.寄存器在构造函数中消息的密钥

GalaSoft.MvvmLight.Extras.SL4.Messenger.Default.Register<NotificationMessage>(this, 
MainPage.EnableButtonKey, message =>{     
// send true if submitting, false if finished 
      // Save or Saving is default 
      this.SaveButton.IsEnabled = message.Content; 

this.SaveButton.Content = message.Notification; }）; } ））;

1. 发送消息来启用或禁用按钮，例如：Messenger.Default.Send>（new NotificationMessage（this，false，“Please Wait ...”），MainPage。SubmitKey）; //重新启用 Messenger.Default.Send>（new NotificationMessage（this，true，originalButtonText），MainPage.SubmitKey）;

Answer 2

由于丹评论说，使用CanExecute来实现禁用逻辑可能会更好。至于改变按钮文本，我会推荐使用绑定到this.IsSubmitting通过ValueConverter选择正确的文本。这最大限度地减少了ViewModel和View之间的交互，因为ViewModel所做的就是说我正在提交，并且View将读取并显示正确的文本。