C# 實作類 QQ 截圖工具 (3/3)：熱鍵註冊、系統匣、單一實例、完整整合

熱鍵註冊 (P/Invoke)

public static class HotKey
{
    [DllImport("user32.dll", SetLastError = true)]
    public static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, Keys vk);

    [DllImport("user32.dll", SetLastError = true)]
    public static extern bool UnregisterHotKey(IntPtr hWnd, int id);

    [Flags]
    public enum Modifiers : uint
    {
        None = 0, Alt = 1, Control = 2, Shift = 4, Win = 8
    }
}

主視窗整合熱鍵與系統匣

public partial class MainForm : Form
{
    private ScreenBody _screenBody;
    private const int HOTKEY_ID = 100;

    public MainForm()
    {
        InitializeComponent();
        // 系統匣選單
        var menu = new ContextMenuStrip();
        menu.Items.Add("設定熱鍵", null, (s,e) => new SetHotKeyForm().ShowDialog());
        menu.Items.Add("結束", null, (s,e) => Application.Exit());
        notifyIcon1.ContextMenuStrip = menu;
        notifyIcon1.Visible = true;
    }

    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);
        RegisterHotKeyFromSettings();
    }

    private void RegisterHotKeyFromSettings()
    {
        uint mod = (uint)HotKey.Modifiers.Control;
        if (Settings.Default.UseAlt) mod |= (uint)HotKey.Modifiers.Alt;
        HotKey.RegisterHotKey(Handle, HOTKEY_ID, mod, Settings.Default.HotKey);
    }

    protected override void WndProc(ref Message m)
    {
        const int WM_HOTKEY = 0x0312;
        if (m.Msg == WM_HOTKEY && m.WParam.ToInt32() == HOTKEY_ID)
            CaptureScreen();
        base.WndProc(ref m);
    }

    private void CaptureScreen()
    {
        // 全螢幕截圖
        Bitmap bmp = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height);
        using (Graphics g = Graphics.FromImage(bmp))
            g.CopyFromScreen(Point.Empty, Point.Empty, Screen.PrimaryScreen.Bounds.Size);

        _screenBody = new ScreenBody { BackgroundImage = bmp };
        _screenBody.Show();
    }

    protected override void OnFormClosing(FormClosingEventArgs e)
    {
        HotKey.UnregisterHotKey(Handle, HOTKEY_ID);
        base.OnFormClosing(e);
    }
}

熱鍵設定視窗

• ComboBox 選擇鍵 (A-Z)、CheckBox 選擇 Ctrl/Alt/Shift/Win 組合。
儲存至 `Settings.Default`，`MainForm` 讀取並重新註冊。

單一實例保護 (Program.cs)

static class Program
{
    [DllImport("User32.dll")] private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);
    [DllImport("User32.dll")] private static extern bool SetForegroundWindow(IntPtr hWnd);
    private const int SW_SHOWNORMAL = 1;

    [STAThread]
    static void Main()
    {
        Process current = Process.GetCurrentProcess();
        Process[] procs = Process.GetProcessesByName(current.ProcessName);
        foreach (var p in procs)
        {
            if (p.Id != current.Id && 
                Assembly.GetExecutingAssembly().Location.Replace("/", "") == p.MainModule.FileName)
            {
                ShowWindowAsync(p.MainWindowHandle, SW_SHOWNORMAL);
                SetForegroundWindow(p.MainWindowHandle);
                return; // 已有實例運行
            }
        }
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new MainForm());
    }
}

游標資源部署

專案資料夾結構：

ScreenCutter/
  Cursors/   hcross.cur, move_m.cur, size1_m.cur, size2_m.cur, size3_m.cur, size4_m.cur
  Icons/     app.ico
  Images/    (可選)

從 `C:\Windows\Cursors` 複製系統游標檔，程式中用相對路徑 `@"..\..\Cursors\xxx.cur"` 載入。

小結

整合熱鍵、系統匣、單一實例、全螢幕截圖、可調整選區矩形，構成功能完整的類 QQ 截圖工具。核心技術點：P/Invoke 熱鍵、WndProc 訊息迴路、Graphics.CopyFromScreen、ControlPaint 反轉繪製、Mutex/Process 單一實例。