在我的 WPF 应用程序中捕获没有焦点的按键事件

我在 WPF 中开发了一个屏幕键盘。我需要夺取钥匙 新闻事件（通过键盘）以跟踪 Caps Lock、Shift 等等（无论它们是否被按下）。 请注意，当任何其他应用程序时，我的应用程序会失去焦点 （比如记事本）被打开。

谁能建议如何在 WPF 中实现这一目标？ 简而言之，我的 WPF 应用程序甚至需要捕获按键事件 虽然它没有焦点。

如果您希望 WPF 应用程序能够检测和处理按键，即使当前未激活或聚焦在屏幕上，您也可以在 Windows 中实现所谓的全局热键。

可以将以下两个方法添加到 C# 类中，以便能够注册和取消注册全局热键：

[DllImport("user32.dll")]
private static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, uint vk);
 
[DllImport("user32.dll")]
private static extern bool UnregisterHotKey(IntPtr hWnd, int id);

示例代码

using System;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;
 
namespace Mm.Wpf.GlobalHotKeys
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        [DllImport("user32.dll")]
        private static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, uint vk);
 
        [DllImport("user32.dll")]
        private static extern bool UnregisterHotKey(IntPtr hWnd, int id);
 
        private const int HOTKEY_ID = 9000;
 
        //Modifiers:
        private const uint MOD_NONE = 0x0000; //(none)
        private const uint MOD_ALT = 0x0001; //ALT
        private const uint MOD_CONTROL = 0x0002; //CTRL
        private const uint MOD_SHIFT = 0x0004; //SHIFT
        private const uint MOD_WIN = 0x0008; //WINDOWS
        //CAPS LOCK:
        private const uint VK_CAPITAL = 0x14;
 
        public MainWindow()
        {
            InitializeComponent();
        }
 
        private IntPtr _windowHandle;
        private HwndSource _source;
        protected override void OnSourceInitialized(EventArgs e)
        {
            base.OnSourceInitialized(e);
 
            _windowHandle = new WindowInteropHelper(this).Handle;
            _source = HwndSource.FromHwnd(_windowHandle);
            _source.AddHook(HwndHook);
 
            RegisterHotKey(_windowHandle, HOTKEY_ID, MOD_CONTROL, VK_CAPITAL); //CTRL + CAPS_LOCK
        }
 
        private IntPtr HwndHook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            const int WM_HOTKEY = 0x0312;
            switch (msg)
            {
                case WM_HOTKEY:
                    switch (wParam.ToInt32())
                    {
                        case HOTKEY_ID:
                            int vkey = (((int)lParam >> 16) & 0xFFFF);
                            if (vkey == VK_CAPITAL)
                            {
                                tblock.Text += "CapsLock was pressed" + Environment.NewLine;
                            }
                            handled = true;
                            break;
                    }
                    break;
            }
            return IntPtr.Zero;
        }
 
        protected override void OnClosed(EventArgs e)
        {
            _source.RemoveHook(HwndHook);
            UnregisterHotKey(_windowHandle, HOTKEY_ID);
            base.OnClosed(e);
        }
    }
}
<Window x:Class="Mm.Wpf.GlobalHotKeys.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">
    <Grid>
        <TextBlock x:Name="tblock"></TextBlock>
    </Grid>
</Window>

参考 https://blog.magnusmontin.net/2015/03/31/implementing-global-hot-keys-in-wpf/