wpf 未执行切换按钮命令
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Toggle button command not executed
提问by Martin
The problem is this. Let's say I have 3 toggle buttons and I want just one being checked at the time using Command. When one button is checked others should be disabled. (I don't want to use radio buttons). So I created this simple code but the strange thing is, that when checked button is clicked commands Execute is not executed (no MessageBox is shown).
问题是这个。假设我有 3 个切换按钮，我希望在使用 Command 时只检查一个。当一个按钮被选中时，其他按钮应该被禁用。（我不想使用单选按钮）。所以我创建了这个简单的代码，但奇怪的是，当单击选中的按钮时，不会执行命令执行（没有显示 MessageBox）。
<Window x:Class="ToggleButtonsProblem.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<StackPanel>
<ToggleButton Command="{Binding ToggleCommand}" CommandParameter="{Binding RelativeSource={RelativeSource Self}}">A</ToggleButton>
<ToggleButton Command="{Binding ToggleCommand}" CommandParameter="{Binding RelativeSource={RelativeSource Self}}">B</ToggleButton>
<ToggleButton Command="{Binding ToggleCommand}" CommandParameter="{Binding RelativeSource={RelativeSource Self}}">C</ToggleButton>
</StackPanel>
using System;
using System.Windows;
using System.Windows.Input;
using System.Windows.Controls.Primitives;
namespace ToggleButtonsProblem {
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window {
public MainWindow() {
InitializeComponent();
this.DataContext = new ViewModel();
}
}
public class ViewModel {
public static ICommand ToggleCommand { get { return new ToggleCommand(); } }
}
public class ToggleCommand : ICommand {
public static bool isSomeChecked = false;
public static ToggleButton currentCheckedButton;
public bool CanExecute(object parameter) {
if (currentCheckedButton == null) return true;
return (parameter as ToggleButton).IsChecked == true;
}
public event EventHandler CanExecuteChanged {
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public void Execute(object parameter) {
currentCheckedButton = null;
ToggleButton button = parameter as ToggleButton;
MessageBox.Show(button.IsChecked.ToString());
if (button.IsChecked == true) {
currentCheckedButton = button;
}
else {
currentCheckedButton = null;
}
}
}
}
}
采纳答案by cre8or
Commands are executed only when button is pressed. You need to hook the Unchecked event of the ToggleButton, for example like this:
仅当按下按钮时才执行命令。您需要挂钩 ToggleButton 的 Unchecked 事件，例如像这样：
<ToggleButton Command="{Binding ToggleCommand}" Unchecked="ToggleButton_Unchecked" CommandParameter="{Binding RelativeSource={RelativeSource Self}}">A</ToggleButton>
And add method handler to the code-behind class:
并将方法处理程序添加到代码隐藏类：
public void ToggleButton_Unchecked(object sender, RoutedEventArgs e) {
(sender as ToggleButton).Command.Execute(sender);
}
This should work, perhaps you can find some prettier way of adding the method handler, maybe as a part of ToggleCommand class.
这应该有效，也许您可以找到一些更漂亮的方法来添加方法处理程序，也许作为 ToggleCommand 类的一部分。
EDIT: Try implementing your CanExecute() method like this:
编辑：尝试像这样实现你的 CanExecute() 方法：
public bool CanExecute(object parameter) {
if (currentCheckedButton == null) return true;
return currentCheckedButton == parameter;
}
For me it works. Here is what I think caused the problem: you click (uncheck) the button, so IsChecked changed to false. Then WPF attempts to invoke the Execute() method, but as always, calls CanExecute() first. However, CanExecute() returns false, because the check state has already been changed, so the Execute() methods is not invoked.
对我来说它有效。这是我认为导致问题的原因：您单击（取消选中）按钮，因此 IsChecked 更改为 false。然后 WPF 尝试调用 Execute() 方法，但与往常一样，首先调用 CanExecute()。但是，CanExecute() 返回 false，因为检查状态已经更改，因此不会调用 Execute() 方法。
回答by user1064519
ToggleCommand should not be static. Try to define the command as a property.
ToggleCommand 不应是静态的。尝试将命令定义为属性。
