wpf Caliburn Micro“进入”关键事件

Caliburn Micro 'Enter' Key Event

提问by spugm1r3

I am attempting to bind an event with Caliburn Micro and I am having some issues getting the right messages to the method. I would like to add the ability to press the 'Enter' key after changing the value in a text box and it execute the same method that the button next to is bound to. However, regardless of which key is pressed, I get the following exceptions:

我正在尝试将事件与 Caliburn Micro 绑定，但在向该方法获取正确消息时遇到了一些问题。我想添加在更改文本框中的值后按“Enter”键的功能，它执行与旁边按钮绑定的相同方法。但是，无论按下哪个键，都会出现以下异常：

A first chance exception of type 'System.InvalidCastException' occurred in MyApp.exe

A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in mscorlib.dll

A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in WindowsBase.dll

MyApp.exe 中发生了“System.InvalidCastException”类型的第一次机会异常

mscorlib.dll 中发生了“System.Reflection.TargetInvocationException”类型的第一次机会异常

WindowsBase.dll 中发生了“System.Reflection.TargetInvocationException”类型的第一次机会异常

At the suggestion of another, similar question Binding KeyDown Event Silverlight, I've tried using ActionExecutionContext, but to no avail.

在另一个类似问题Binding KeyDown Event Silverlight的建议下，我尝试使用 ActionExecutionContext，但无济于事。

Here is the xaml:

这是xaml：

<TextBox Name="Threshold"                     
              Margin="5"
              Grid.Column="1"
              >
     <i:Interaction.Triggers>
         <i:EventTrigger EventName="KeyDown">
             <cal:ActionMessage MethodName="ExecuteFilterView">
                 <cal:Parameter Value="$executionContext"/>
             </cal:ActionMessage>
         </i:EventTrigger>
     </i:Interaction.Triggers>
</TextBox>

And the method:

和方法：

 public void ExecuteFilterView(ActionExecutionContext context)
    {
        //Do stuff...
    }

I understand that I could probably save myself some headaches and simply do a standard event handler in the code behind, but this app is an exercise in MVVM and learning to utilize Caliburn.Micro, so I would like to stick with making this particular approach work.

我知道我可能会为自己省去一些麻烦，只需在后面的代码中做一个标准的事件处理程序，但这个应用程序是 MVVM 中的一个练习，并学习使用 Caliburn.Micro，所以我想坚持让这种特殊的方法起作用.

Am I just trying to send the wrong information from the event? Is my xaml not coded properly to get what I want? Or I have missed something else entirely?

我只是想从事件中发送错误的信息吗？我的 xaml 是否没有正确编码以获得我想要的？或者我完全错过了其他东西？

回答by Charleh

Just threw a test together, both of these work for me:

刚刚进行了一个测试，这两个都对我有用：

Using full syntax:

使用完整语法：

    <TextBox Name="Threshold"                     
          Margin="5"
          Grid.Column="1">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="KeyDown">
                <cal:ActionMessage MethodName="ExecuteFilterView">
                    <cal:Parameter Value="$executionContext"/>
                </cal:ActionMessage>
            </i:EventTrigger>
        </i:Interaction.Triggers>
    </TextBox>

Using CM syntax (prefer this as it's way more readable)

使用 CM 语法（更喜欢这个，因为它更具可读性）

    <TextBox Name="Threshold"                     
          Margin="5"
          Grid.Column="1"
          cal:Message.Attach="[Event KeyDown] = [Action ExecuteFilterView($executionContext)]" />            

This was the test VM:

这是测试虚拟机：

public class MainWindowViewModel
{
    public void ExecuteFilterView(ActionExecutionContext context)
    { 
        // This method is hit and the context is present and correct
    }
}

Can you post your full code - are you sure you have the framework setup correctly? (have you followed the getting started example?

你能发布你的完整代码 - 你确定你的框架设置正确吗？（您是否遵循了入门示例？

http://caliburnmicro.codeplex.com/wikipage?title=Basic%20Configuration%2c%20Actions%20and%20Conventions&referringTitle=Documentation

http://caliburnmicro.codeplex.com/wikipage?title=Basic%20Configuration%2c%20Actions%20and%20Conventions&referringTitle=文档

Edit:

编辑：

Ok after your clarification I can give you some examples of how to do this - I'll tell you my personal preference and why, but choose the one that fits you best

好的，在您澄清之后，我可以给您一些如何执行此操作的示例 - 我会告诉您我的个人偏好以及原因，但请选择最适合您的

1. Using ActionExecutionContextand casting the eventargs:

1. 使用ActionExecutionContext和转换 eventargs：

    cal:Message.Attach="[Event KeyDown] = [Action ExecuteFilterView($executionContext)]"

    public void ExecuteFilterView(ActionExecutionContext context)
    {
        var keyArgs = context.EventArgs as KeyEventArgs;

        if (keyArgs != null && keyArgs.Key == Key.Enter)
        {
            // Do Stuff
        }
    }

1. Using EventArgsdirectly

2. EventArgs直接使用

    cal:Message.Attach="[Event KeyDown] = [Action ExecuteFilterView($eventArgs)]"

    public void ExecuteFilterView(KeyEventArgs keyArgs)
    {
        if (keyArgs.Key == Key.Enter)
        {
            // Do Stuff
        }
    }

1. My personal fave, creating your own SpecialValuesdictionary entry:

3. 我个人的最爱，创建自己的SpecialValues字典条目：

In your Bootstrapper.Configuremethod...

在你的Bootstrapper.Configure方法...

MessageBinder.SpecialValues.Add("$pressedkey", (context) =>
{
    // NOTE: IMPORTANT - you MUST add the dictionary key as lowercase as CM
    // does a ToLower on the param string you add in the action message, in fact ideally
    // all your param messages should be lowercase just in case. I don't really like this
    // behaviour but that's how it is!
    var keyArgs = context.EventArgs as KeyEventArgs;

    if (keyArgs != null)
        return keyArgs.Key;

    return null;
});

Your action:

你的行动：

cal:Message.Attach="[Event KeyDown] = [Action ExecuteFilterView($pressedKey)]"

And the code:

和代码：

public void ExecuteFilterView(Key key)
{
    if (key == Key.Enter)
    {
        // Do Stuff
    }
}

The reason this is my favourite? It means that your VM just receives the value you want (most of the time you don't care about a lot of the other parameters) and you don't need to know how to or bother to cast the eventargs - you can just operate on the value. Obviously use whatever is best for you

这是我最喜欢的原因？这意味着您的 VM 只会收到您想要的值（大多数时候您并不关心很多其他参数）并且您不需要知道如何或费心去转换 eventargs - 您可以直接操作在价值上。显然使用最适合你的

It's also worth noting, that if you have other types of controls that subclass KeyEventArgsthis will work for them. If they don't subclass KeyEventArgsbut they still return a value of type Keythis will still work too as you can just add another cast to the delegate if the first one fails:

还值得注意的是，如果您有其他类型的控件子类，KeyEventArgs这将适用于它们。如果他们没有子类化KeyEventArgs但他们仍然返回一个类型的值，Key这仍然可以工作，因为如果第一个失败，您可以向委托添加另一个强制转换：

e.g.

例如

MessageBinder.SpecialValues.Add("$pressedkey", (context) =>
{
    var keyArgs = context.EventArgs as KeyEventArgs;

    if (keyArgs != null)
        return keyArgs.Key;

    // Ok so it wasn't KeyEventArgs... check for some other type - maybe a 3rd party implementation
    var thirdPartyKeyArgs = context.EventArgs as ThirdPartyKeyArgs;

    if (thirdPartyKeyArgs != null)
        return thirdPartyKeyArgs.KeyProperty;

    return null;
});

回答by kuberzzz333

If using keyeventargs as parameter type , and it gives u back null ,then look at this: You propably using System.Windows.Forms.KeyEventArgsand KeyEventArgs, as parameter type is refering to this, try with System.Windows.Input.KeyEventArgs(it works for me).

如果使用 keyeventargs 作为参数类型，并且它给你返回 null ，那么看看这个：你可能使用System.Windows.Forms.KeyEventArgsand KeyEventArgs，因为参数类型是指这个，试试System.Windows.Input.KeyEventArgs（它对我有用）。

public void ExecuteFilterView(System.Windows.Input.KeyEventArgs context)
{
     if(context.Key==System.Windows.Input.Key.Return)
     {
         //action here
     }      
}