WPF：命令阻碍按钮启用

Question

我有 2 个按钮.. 一开始，其中一个已启用，另一个未启用。然后我对这些按钮有 2 个命令，我需要为它们实现键绑定。这些命令也应该替换按钮的点击方法。

当第一个按钮被点击时，第二个按钮应该被启用。但它不起作用。如果我删除第二个按钮的命令并添加一个点击方法，它会起作用..

xaml:

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApplication1"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <RoutedUICommand x:Key="first" />
        <RoutedUICommand x:Key="second" />
    </Window.Resources>
    <Window.CommandBindings>
        <CommandBinding Command="{StaticResource first}" Executed="CommandBinding_Executed_1" />
        <CommandBinding Command="{StaticResource second}" CanExecute="CommandBinding_CanExecute" Executed="CommandBinding_Executed" />
    </Window.CommandBindings>
    <Window.InputBindings>
        <KeyBinding Key="F4" Command="{StaticResource first}" />
        <KeyBinding Key="F5" Command="{StaticResource second}" />
    </Window.InputBindings>
    <Grid>
        <Button Command="{StaticResource first}" x:Name="button" Content="Button" HorizontalAlignment="Left" Margin="154,146,0,0" VerticalAlignment="Top" Width="75"/>
        <Button Command="{StaticResource second}" IsEnabled="False" x:Name="button1" Content="Button" HorizontalAlignment="Left" Margin="312,146,0,0" VerticalAlignment="Top" Width="75"/>
    </Grid>
</Window>

xaml.cs

using System.Windows;
    using System.Windows.Input;

    namespace WpfApplication1 {
        /// <summary>
        /// Interaction logic for MainWindow.xaml
        /// </summary>
        public partial class MainWindow : Window {
            public MainWindow() {
                InitializeComponent();
            }

            private void CommandBinding_Executed(object sender, ExecutedRoutedEventArgs e) {
                MessageBox.Show("Test");
            }

            private void CommandBinding_CanExecute(object sender, CanExecuteRoutedEventArgs e) {
                e.CanExecute = button1.IsEnabled;
            }

            private void CommandBinding_Executed_1(object sender, ExecutedRoutedEventArgs e) {
                button1.IsEnabled = true;
            }
        }
    }

Answer 1

定义CanExecute时，按钮根据e.CanExecute的值启用或禁用，因此显式设置IsEnabled无效，因为它是隐式设置的。

您可以引入一个由 CommandBinding_CanExecute 返回的变量 - 据我所知，这将产生预期的效果。

public partial class MainWindow : Window {

    // other details elided

    bool _enableButton1 = false;

    private void CommandBinding_CanExecute(object sender, CanExecuteRoutedEventArgs e) {
        e.CanExecute = _enableButton1;
    }

    private void CommandBinding_Executed_1(object sender, ExecutedRoutedEventArgs e) {
        enableButton1 = true;
    }
}

无论如何，您可以完全省略 CanExecute-action 并明确设置 IsEnabled。这也可以解决问题。

public partial class MainWindow : Window {

    // elided

    private void CommandBinding_Executed_1(object sender, ExecutedRoutedEventArgs e) {
        button1.IsEnabled = true;
    }
}

Answer 2

为什么是 Button.IsEnabledDoesNotWork？ 以为是在 XAML 中设置的

因为 Command 会覆盖 IsEnabled 功能。

  public partial class SampleWindow : Window
    {
        private bool _isButton1Enabled = false;
        public SampleWindow()
        {
            InitializeComponent();
        }

        private void CommandBinding_Executed(object sender, ExecutedRoutedEventArgs e)
        {
            MessageBox.Show("Test");
        }

        private void CommandBinding_CanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            try
            {
                e.CanExecute = _isButton1Enabled;
            }
            catch (Exception)
            {

                throw;
            }
        }


        private void CommandBinding_Executed_1(object sender, ExecutedRoutedEventArgs e)
        {
            _isButton1Enabled = true;

        }
    }