如何将单选按钮的IsChecked属性传递为命令参数。

huangapple
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英文:

How to pass radio button IsChecked property as command parameter

问题

You can pass the IsChecked property as a parameter to your command using Xamarin.Forms behaviors. To fix the exception issue, you should make sure that the ChangeCurrentPlayer method has the correct signature to accept a boolean parameter. Here's how you can modify your XAML and method:

XAML:

  1. <RadioButton x:Name="radioButton1"
  2.              Value="Player1"
  3.              Grid.Row="0"
  4.              Grid.ColumnSpan="2"
  5.              BorderWidth="1"
  6.              VerticalOptions="Center"
  7.              IsChecked="True">
  8.     <RadioButton.Content>
  9.         <MultiBinding StringFormat="{}{0} {1}">
  10.             <Binding Path="Name1"/>
  11.             <Binding Path="Player1.Score"/>
  12.         </MultiBinding>
  13.     </RadioButton.Content>
  14.     <RadioButton.Behaviors>
  15.         <toolkit:EventToCommandBehavior
  16.             EventName="CheckedChanged"
  17.             Command="{Binding ChangeCurrentPlayerCommand}"
  18.             CommandParameter="{Binding Source={x:Reference radioButton1}, Path=IsChecked}"/>
  19.     </RadioButton.Behaviors>
  20. </RadioButton>

C# ViewModel:

  1. [RelayCommand]
  2. void ChangeCurrentPlayer(bool isChecked)
  3. {
  4.     if (isChecked)
  5.     {
  6.         CurrentPlayer = Player1;
  7.     }
  8.     else
  9.     {
  10.         CurrentPlayer = Player2;
  11.     }
  12. }

By using {Binding Source={x:Reference radioButton1}, Path=IsChecked}, you pass the IsChecked property of the specific radioButton1 instance as a parameter to your ChangeCurrentPlayer command. This should help you determine which button is currently calling the command without encountering the "Operation is not valid" exception.

英文:

Right now I have a xaml page in MAUI .Net with the following radio button

  1. &lt;RadioButton x:Name=&quot;radioButton1&quot;
  2.                      Value=&quot;Player1&quot;
  3.                      Grid.Row=&quot;0&quot;
  4.                      Grid.ColumnSpan=&quot;2&quot;
  5.                      BorderWidth=&quot;1&quot;
  6.                      VerticalOptions=&quot;Center&quot;
  7.                      IsChecked= &quot;True&quot;
  8.                      &gt;
  9.             
  10.             &lt;RadioButton.Content&gt;
  11.                 &lt;MultiBinding StringFormat=&quot;{}{0} {1}&quot;&gt;
  12.                     &lt;Binding Path=&quot;Name1&quot;/&gt;
  13.                     &lt;Binding Path=&quot;Player1.Score&quot;/&gt;
  14.                 &lt;/MultiBinding&gt;
  15.             &lt;/RadioButton.Content&gt;
  16.             &lt;RadioButton.Behaviors&gt;
  17.                 &lt;toolkit:EventToCommandBehavior
  18.                         EventName=&quot;CheckedChanged&quot;
  19.                         Command=&quot;{Binding ChangeCurrentPlayerCommand}&quot;
  20.                         CommandParameter=&quot;{Binding Source={RelativeSource Self}, Path=IsChecked}&quot;
  21.                     /&gt;
  22.             &lt;/RadioButton.Behaviors&gt;
  23.         &lt;/RadioButton&gt;

And I the command is the following method on my ViewModel.

  1. [RelayCommand]
  2.         void ChangeCurrentPlayer()
  3.         {
  5.             if (CurrentPlayer == Player1)
  6.             {
  7.                 CurrentPlayer = Player2;
  8.             }
  9.             else
  10.             {
  11.                 CurrentPlayer = Player1;
  12.             }
  14.         }

I want to pass the IsChecked property of the button as a parameter to the command, but the application throws an exception of type:

  1. System.InvalidOperationException: &#39;Operation is not valid due to the current state of the object.&#39;

Is there any way I can do this?
The reason I need to pass that state as an argument is to get around the fact that whenever a radio button is clicked the command is fired twice in a row, making it useless, unless I have a way to know which button is currently calling it.

答案1

得分: 0

行为没有唯一的可视树父级，因此我们无法在其上使用RelativeSource绑定。请参考此问题：Relativesource bindings and behaviors。

作为一种解决方法，您可以尝试以下方法。

在XAML中，更改CommandParameter的绑定：

  1. <StackLayout>
  2.     <RadioButton x:Name="radioButton1"
  3.          ...
  4.          VerticalOptions="Center"
  5.          IsChecked="True"
  6.          >
  7.         ...
  8.         <RadioButton.Behaviors>
  9.             <toolkit:EventToCommandBehavior
  10.             EventName="CheckedChanged"
  11.             Command="{Binding ChangeCurrentPlayerCommand}"
  12.             CommandParameter="{Binding Source={x:Reference radioButton1}, Path=IsChecked}"
  13.         />
  14.         </RadioButton.Behaviors>
  15.     </RadioButton>
  16. </StackLayout>

这将CommandParameter绑定到radiobutton1的IsChecked属性。

在viewModel中，传递正确的参数（IsChecked是bool类型），像这样：

  1. [RelayCommand]
  2. void ChangeCurrentPlayer(bool isChecked)
  3. {
  4.     var a = isChecked;   
  5.     Console.WriteLine("123");
  6. }

希望它能正常工作。

英文:

Behaviours don't have unique visual tree parents so we cannot use RelativeSource binding on it. Please refer to this issue: Relativesource bindings and behaviors.

As a workaround, you could try the following method.

in xaml, change the Binding for CommandParameter:

  1. &lt;StackLayout&gt;
  2.     &lt;RadioButton x:Name=&quot;radioButton1&quot;
  3.          ...
  4.          VerticalOptions=&quot;Center&quot;
  5.          IsChecked= &quot;True&quot;
  6.          &gt;
  7.         ...
  8.         &lt;RadioButton.Behaviors&gt;
  9.             &lt;toolkit:EventToCommandBehavior
  10.             EventName=&quot;CheckedChanged&quot;
  11.             Command=&quot;{Binding ChangeCurrentPlayerCommand}&quot;
  12.             CommandParameter=&quot;{Binding Source={x:Reference radioButton1}, Path=IsChecked}&quot;
  13.         /&gt;
  14.         &lt;/RadioButton.Behaviors&gt;
  15.     &lt;/RadioButton&gt;

This binds the CommandParameter to the IsChecked Property of this radiobutton1.

And in viewModel, pass the correct parameter (IsChecked is bool type), like this:

  1. [RelayCommand]
  2. void ChangeCurrentPlayer(bool isChecked)
  3. {
  4.     var a = isChecked;   
  5.     Console.WriteLine(&quot;123&quot;);
  6. }

Hope it works.

huangapple
  • 本文由 发表于 2023年5月15日 07:56:17
  • 转载请务必保留本文链接：https://go.coder-hub.com/76250155.html
  • c#
  • maui
  • mvvm
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