如何使用 Windows API 重新打开已关闭的 window

Question

我在主 window ( hwnd ) 中制作了一个按钮，当你点击一个按钮时，它会打开新的 window ( hwndSec )，它可以由主 window！当我点击一个按钮时，hwndSec 出现了！当我点击其他按钮时，它可以被修改......但是当我关闭它并尝试再次打开它时它没有响应！所以按钮变得无用了！
这是单个按钮的简单示例，仅用于打开 window 然后尝试再次打开它。

我为 hwndSec 设置的设置：

wincl.hInstance = hInstance;
wincl.lpszClassName = "HwndSecClass";
wincl.lpfnWndProc = WindowProcedureSec;      
wincl.style = CS_DBLCLKS;                 
wincl.cbSize = sizeof (WNDCLASSEX);

/* Use default icon and mouse-pointer */
wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
wincl.lpszMenuName = NULL;                 
wincl.cbClsExtra = 0;                      
wincl.cbWndExtra = 0;                      
wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;

if (!RegisterClassEx (&wincl))
    return 0;

hwnd = CreateWindowEx (
       0,                   
       wincl.lpszClassName,        
       _T("Window 2"),       
       WS_OVERLAPPEDWINDOW, 
       CW_USEDEFAULT,       
       CW_USEDEFAULT,       
       500,                 
       500,                 
       HWND_DESKTOP,        
       NULL,                
       hInstance,       
       NULL                
       );

我做了两个window程序：

LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK WindowProcedureSec (HWND, UINT, WPARAM, LPARAM);

当我点击一个按钮时，我调用这个函数：

ShowWindow(hwndSec,SW_SHOW);

然后第二个 window 正常出现，当我关闭 window 它不会再次出现。

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
 switch (message)                  /* handle the messages */
 {
 case WM_CREATE:
    CreateWindow("BUTTON",
                "open",
                WS_CHILD | WS_VISIBLE ,
                200,100,
                100,50,
                hwnd,
                (HMENU) ID_BUTTON,
                NULL,
                NULL);
    break;
case WM_COMMAND:
    switch(LOWORD(wParam))
    {
    case ID_BUTTON :
        //printf("%s",(char*)GetLastError());
        ShowWindow(hwndSec,SW_SHOW);
        break;
    }
    break;
    case WM_DESTROY:
        PostQuitMessage (0);
        break;
    default:
        return DefWindowProc (hwnd, message, wParam, lParam);
}

return 0;
}


LRESULT CALLBACK WindowProcedureSec (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
switch (message)
{
    case WM_DESTROY:
        PostMessage(hwnd, WM_CLOSE, 0, 0);
        break;
    default:
        return DefWindowProc (hwnd, message, wParam, lParam);
}
return 0;
}

Answer 1

当 window 被关闭时，它会收到一条 WM_CLOSE 消息。如果该消息传递给 DefWindowProc()，默认行为是 销毁 window:

An application can prompt the user for confirmation, prior to destroying a window, by processing the WM_CLOSE message and calling the DestroyWindow function only if the user confirms the choice.

By default, the DefWindowProc function calls the DestroyWindow function to destroy the window.

这在 MSDN 上有进一步讨论：

Closing the Window

因此，每次您想要在关闭后显示它时，您都必须使用 CreateWindow/Ex() 重新创建您的辅助 window：

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    ...
    case WM_COMMAND:
        switch (LOWORD(wParam))
        {
        case ID_BUTTON :
            if (!hwndSec)
            {
                hwndSec = CreateWindowEx(
                    0,
                    _T("HwndSecClass"),
                    _T("Window 2"),
                    WS_OVERLAPPEDWINDOW,
                    CW_USEDEFAULT,
                    CW_USEDEFAULT,
                    500,
                    500,
                    HWND_DESKTOP,
                    NULL,
                    hInstance,
                    NULL
                );
            }
            ShowWindow(hwndSec, SW_SHOW);
            break;
        }
        break;
    ...
    }

    return 0;
}

LRESULT CALLBACK WindowProcedureSec (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_DESTROY:
        hwndSec = NULL;
        break;
    }

    return DefWindowProc(hwnd, message, wParam, lParam);
}

如果您不想这样做，则需要让辅助 window 处理 WM_CLOSE 消息，而不是将其传递给 DefWindowProc()。例如，改为调用 ShowWindow(SW_HIDE)，然后您可以稍后在需要时调用 ShowWindow(SH_SHOW)

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    ...
    case WM_COMMAND:
        switch (LOWORD(wParam))
        {
        case ID_BUTTON :
            ShowWindow(hwndSec, SW_SHOW);
            break;
        }
        break;
    ...
    }

    return 0;
}


LRESULT CALLBACK WindowProcedureSec (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_CLOSE:
        ShowWindow(hwnd, SW_HIDE);
        break;

    default:
        return DefWindowProc(hwnd, message, wParam, lParam);
    }

    return 0;
}

如何使用 Windows API 重新打开已关闭的 window

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