C# 如何将键盘输入命令绑定到主窗口？

我对WPF绑定比较陌生，在绑定

ICommand

实现的类（用于检测窗口中的用户键盘输入）时遇到困难？起初，我认为需要将它绑定到XAML上的窗口，但该窗口似乎没有

命令

这是我的ViewModel类

public class NoteBoxViewModel
{
    public MusicalNotation MusicalNotation { get; set; }
    public ICommand KeyboardHotkeyCommand { get; private set; }
    public bool IsSelected { get; set; }

    public NoteBoxViewModel()
    {
        MusicalNotation = new MusicalNotation();
        KeyboardHotkeyCommand = new KeyboardHotkeyCommand(this);
        IsSelected = true;
    }
}

public class KeyboardHotkeyCommand : ICommand
{
    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    private NoteBoxViewModel _vm;

    public KeyboardHotkeyCommand(NoteBoxViewModel vm)
    {
        _vm = vm;
    }

    public bool CanExecute(object parameter)
    {
        return _vm.IsSelected;
    }

    public void Execute(object parameter)
    {
        if (Keyboard.IsKeyDown(Key.OemPeriod))
        {
            _vm.MusicalNotation.Note = Notes.Blank;
        }
        else if (Keyboard.IsKeyDown(Key.D0))
        {
            _vm.MusicalNotation.Note = Notes.Rest;
        }
        else if (Keyboard.IsKeyDown(Key.D1))
        {
            _vm.MusicalNotation.Note = Notes.N1;
        }
        else if (Keyboard.IsKeyDown(Key.D2))
        {
            _vm.MusicalNotation.Note = Notes.N2;
        }
        else if (Keyboard.IsKeyDown(Key.D3))
        {
            _vm.MusicalNotation.Note = Notes.N3;
        }
        else if (Keyboard.IsKeyDown(Key.D4))
        {
            _vm.MusicalNotation.Note = Notes.N4;
        }
        else if (Keyboard.IsKeyDown(Key.D5))
        {
            _vm.MusicalNotation.Note = Notes.N5;
        }
        else if (Keyboard.IsKeyDown(Key.D6))
        {
            _vm.MusicalNotation.Note = Notes.N6;
        }
        else if (Keyboard.IsKeyDown(Key.D7))
        {
            _vm.MusicalNotation.Note = Notes.N7;
        }
        else if (Keyboard.Modifiers == ModifierKeys.Control && Keyboard.IsKeyDown(Key.OemPlus))
        {
            _vm.MusicalNotation.Octave++;
        }
        else if (Keyboard.Modifiers == ModifierKeys.Control && Keyboard.IsKeyDown(Key.OemMinus))
        {
            _vm.MusicalNotation.Octave--;
        }
    }
}

这是我的KeyboardHotkeyCommand类

public class NoteBoxViewModel
{
    public MusicalNotation MusicalNotation { get; set; }
    public ICommand KeyboardHotkeyCommand { get; private set; }
    public bool IsSelected { get; set; }

    public NoteBoxViewModel()
    {
        MusicalNotation = new MusicalNotation();
        KeyboardHotkeyCommand = new KeyboardHotkeyCommand(this);
        IsSelected = true;
    }
}

public class KeyboardHotkeyCommand : ICommand
{
    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    private NoteBoxViewModel _vm;

    public KeyboardHotkeyCommand(NoteBoxViewModel vm)
    {
        _vm = vm;
    }

    public bool CanExecute(object parameter)
    {
        return _vm.IsSelected;
    }

    public void Execute(object parameter)
    {
        if (Keyboard.IsKeyDown(Key.OemPeriod))
        {
            _vm.MusicalNotation.Note = Notes.Blank;
        }
        else if (Keyboard.IsKeyDown(Key.D0))
        {
            _vm.MusicalNotation.Note = Notes.Rest;
        }
        else if (Keyboard.IsKeyDown(Key.D1))
        {
            _vm.MusicalNotation.Note = Notes.N1;
        }
        else if (Keyboard.IsKeyDown(Key.D2))
        {
            _vm.MusicalNotation.Note = Notes.N2;
        }
        else if (Keyboard.IsKeyDown(Key.D3))
        {
            _vm.MusicalNotation.Note = Notes.N3;
        }
        else if (Keyboard.IsKeyDown(Key.D4))
        {
            _vm.MusicalNotation.Note = Notes.N4;
        }
        else if (Keyboard.IsKeyDown(Key.D5))
        {
            _vm.MusicalNotation.Note = Notes.N5;
        }
        else if (Keyboard.IsKeyDown(Key.D6))
        {
            _vm.MusicalNotation.Note = Notes.N6;
        }
        else if (Keyboard.IsKeyDown(Key.D7))
        {
            _vm.MusicalNotation.Note = Notes.N7;
        }
        else if (Keyboard.Modifiers == ModifierKeys.Control && Keyboard.IsKeyDown(Key.OemPlus))
        {
            _vm.MusicalNotation.Octave++;
        }
        else if (Keyboard.Modifiers == ModifierKeys.Control && Keyboard.IsKeyDown(Key.OemMinus))
        {
            _vm.MusicalNotation.Octave--;
        }
    }
}

这是我的笔记枚举

public enum Notes
{
    N1,
    N2,
    N3,
    N4,
    N5,
    N6,
    N7,
    Rest,
    Blank
}

问题:

如何将
KeyboardHotkeyCommand
绑定到我的XAML类，以便检测用户输入（input不会首先进入
Textbox
或任何类型的文本编辑器）？我还尝试将它绑定到
窗口_IsKeyDown
（我知道这是一个糟糕的做法），但最终失败了。是否可以在没有
事件的情况下实现它

在我的
KeyboardHotkeyCommand
中，有一个名为
CanExecuteChanged
的事件。我在上面填上了确切的方向，上面说的是：。但我不知道为什么会这样。谁能给我解释一下吗
我还研究了这里的教程：他似乎可以用
ActionCommand
直接实例化
ICommand
，但在我的VisualStudio中找不到。有人知道为什么吗
注:

尽管我是MVVM新手（昨天才知道），但我希望尽可能多地使用MVVM模式，因此，我希望避免使用事件（当然，如果可能的话），因为我读到这不是一个好的MVVM实践
我认为，无论我的
MusicalNotation
类是什么样子，它都不会影响这个问题的解决，因为它只是一个“模型”。但如果需要的话，我也会百分之百地向你展示
使用MVVM模式，您可以使用主窗口上的
InputBindings
将击键绑定到VM命令。示例
Xaml
代码段如下所示

<Window.InputBindings>
    <KeyBinding Key="Right" Command="{Binding NavigateCommand}" CommandParameter="f"/>
    <KeyBinding Key="Left" Command="{Binding NavigateCommand}" CommandParameter="b"/>
    <KeyBinding Key="Delete"  Command="{Binding NavigateCommand}"  CommandParameter="delete"/>
    <KeyBinding Key="F5" Command="{Binding GetAllCommand}"/>
</Window.InputBindings>

<Window.InputBindings>
    <KeyBinding Key="A"  Command="{Binding KeyBoardHotKeyCommand}" CommandParameter="N1"/>
</Window.InputBindings>

public class RelayCommand : ICommand
{   //http://msdn.microsoft.com/en-us/magazine/dd419663.aspx
    public RelayCommand(Action<object> execute, Predicate<object> canExecute)
    {
        _execute = execute;
        _canExecute = canExecute;
    }
    public bool CanExecute(object parameter)
    {
        return _canExecute(parameter);
    }
    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }
    public void Execute(object parameter)
    {
        _execute(parameter);
    }
    private readonly Action<object> _execute;
    private readonly Predicate<object> _canExecute;
}

    public ICommand KeyBoardHotKeyCommand { get; set; }
    public ViewModel()
    {
        KeyBoardHotKeyCommand = new RelayCommand(ExecuteKeyboardHotKeyCommand, CanExecuteKeyboardHotKeyCommand);
    }
    private void ExecuteKeyboardHotKeyCommand(object obj)
    {
        Notes note;
        if (obj!=null && Enum.TryParse(obj.ToString(), out note))
        {
            Console.WriteLine(@"User pressed {0}", note);
        }
    }
    private bool CanExecuteKeyboardHotKeyCommand(object obj)
    {
        return true;
    }

使用ICommand代理，如

    private void ExecuteKeyboardHotKeyCommand(object obj)
    {
        Notes note;
        if (obj!=null && Enum.TryParse(obj.ToString(), out note))
        {
            Console.WriteLine(@"User pressed {0}", note);
        }
    }
    private bool CanExecuteKeyboardHotKeyCommand(object obj)
    {
        return true;
    }

您的“Notes”枚举很好。您的
ICommand
代理在MVVM方面走的是正确的道路，但需要从
Keyboard.IsKeyDown中抽象出来，因为这些引用不容易测试。写得好的视图模型与硬件无关，并不真正关心事件是否发生在键盘或其他设备（如触摸屏）上

对于最后一个问题，我使用Josh Smith的
RelayCommand
。看起来像这样

<Window.InputBindings>
    <KeyBinding Key="Right" Command="{Binding NavigateCommand}" CommandParameter="f"/>
    <KeyBinding Key="Left" Command="{Binding NavigateCommand}" CommandParameter="b"/>
    <KeyBinding Key="Delete"  Command="{Binding NavigateCommand}"  CommandParameter="delete"/>
    <KeyBinding Key="F5" Command="{Binding GetAllCommand}"/>
</Window.InputBindings>

<Window.InputBindings>
    <KeyBinding Key="A"  Command="{Binding KeyBoardHotKeyCommand}" CommandParameter="N1"/>
</Window.InputBindings>

public class RelayCommand : ICommand
{   //http://msdn.microsoft.com/en-us/magazine/dd419663.aspx
    public RelayCommand(Action<object> execute, Predicate<object> canExecute)
    {
        _execute = execute;
        _canExecute = canExecute;
    }
    public bool CanExecute(object parameter)
    {
        return _canExecute(parameter);
    }
    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }
    public void Execute(object parameter)
    {
        _execute(parameter);
    }
    private readonly Action<object> _execute;
    private readonly Predicate<object> _canExecute;
}

    public ICommand KeyBoardHotKeyCommand { get; set; }
    public ViewModel()
    {
        KeyBoardHotKeyCommand = new RelayCommand(ExecuteKeyboardHotKeyCommand, CanExecuteKeyboardHotKeyCommand);
    }
    private void ExecuteKeyboardHotKeyCommand(object obj)
    {
        Notes note;
        if (obj!=null && Enum.TryParse(obj.ToString(), out note))
        {
            Console.WriteLine(@"User pressed {0}", note);
        }
    }
    private bool CanExecuteKeyboardHotKeyCommand(object obj)
    {
        return true;
    }

最后，关于Reed的实施问题，当美国的会员们醒来时，Reed可能会在场。但就目前而言，他的
ActionCommand
（现在是Expression Studio的一部分
)基本上与Josh Smith的
RelayCommand

相同。它们都使用相同的原则来实现

ICommand

接口。

如果可能，请您也回答第2个问题好吗？第2个和第3个问题已修改如果可能，您能否进一步解释一下：

添加{CommandManager.RequerySuggested+=value；}

和

删除{CommandManager.RequerySuggested-=value；}

？谢谢。你能读一下吗？如果有什么不清楚的地方，那就形成另一个问题？我有。嗯。那么，value是要绑定的元素吗？如果是，那我就有点明白了。