WPF MVVM密钥绑定

Question

我是WPF的新手，我编写的代码似乎不起作用。当按下向左箭头键时，我试图向左移动一个矩形划片，但当按下向左方向键时，没有得到任何响应。我在这里做错了什么？

这是视图：

<UserControl.InputBindings>
<KeyBinding Key="Left" Command="{Binding MovePaddleLeftCommand}"/>
</UserControl.InputBindings>

这是ViewModel中的代码：

private ICommand _movePaddleLeftCommand;
public ICommand MovePaddleLeftCommand
{
get
{
return new DelegateCommand(ExecuteCommand, CanExecute);
}
}
private void ExecuteCommand()
{
MessageBox.Show("Left");
MovePaddleLeft();
}
private bool CanExecute()
{
return true;
}

下面是一个更完整的代码图片，以防与之相关。

GameView.xaml:

<UserControl x:Class="Arkanoid_MkII.Views.GameView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
xmlns:local="clr-namespace:Arkanoid_MkII.Views"
mc:Ignorable="d"
Width="1500" Height="800">
<Canvas Name="GameArea" ClipToBounds="True">
<Rectangle Canvas.Left="{Binding Path=Paddle.PaddleX}" Canvas.Top="750" Width="{Binding Path=Paddle.Width}" Height="{Binding Path=Paddle.Height}" Fill="{Binding Path=Paddle.Colour}"/>
</Canvas>
<UserControl.InputBindings>
<KeyBinding Key="Left" Command="{Binding MovePaddleLeftCommand}"/>
</UserControl.InputBindings>
</UserControl>

GameView.xaml.cs:

public partial class GameView : UserControl
{
public GameView()
{
InitializeComponent();
}
}

主窗口.xaml:

<Window x:Class="Arkanoid_MkII.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:Arkanoid_MkII"
xmlns:views="clr-namespace:Arkanoid_MkII.Views"
mc:Ignorable="d"
Title="MainWindow" SizeToContent="WidthAndHeight" ResizeMode="NoResize" Background="Black" Padding="100">
<Grid>
<Border BorderBrush="Black" BorderThickness="5">
<views:GameView x:Name="GameViewControl" Loaded="GameViewControl_Loaded" />
</Border>
</Grid>
</Window>

主窗口.xaml.cs:

public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void GameViewControl_Loaded(object sender, RoutedEventArgs e)
{
Arkanoid_MkII.ViewModels.GameViewModel gameViewModelObject = new Arkanoid_MkII.ViewModels.GameViewModel();
GameViewControl.DataContext = gameViewModelObject;
}
}

GameViewModel.cs:

private ICommand _movePaddleLeftCommand;
public ICommand MovePaddleLeftCommand
{
get
{
return new DelegateCommand(ExecuteCommand, CanExecute);
}
}
private void ExecuteCommand()
{
MessageBox.Show("Left");
MovePaddleLeft();
}
private bool CanExecute()
{
return true;
}

Answer 1

UserControl必须是可聚焦的，并且是要执行的命令的焦点：

private void GameViewControl_Loaded(object sender, RoutedEventArgs e)
{
Arkanoid_MkII.ViewModels.GameViewModel gameViewModelObject = 
new Arkanoid_MkII.ViewModels.GameViewModel();
GameViewControl.DataContext = gameViewModelObject;
GameViewControl.Focusable = true;
Keyboard.Focus(GameViewControl);
}