为什么 FindWindowEx 找不到 IP 地址窗口？

Question

如下创建了一个IP地址窗口，然后尝试使用FindWindowEx函数找到它：

    INITCOMMONCONTROLSEX icex;
    icex.dwSize = sizeof(INITCOMMONCONTROLSEX);
    icex.dwICC = ICC_INTERNET_CLASSES;
    InitCommonControlsEx(&icex);

    // hwnd is the parent of the IP address window
    HWND eIpAddress = CreateWindowW(WC_IPADDRESS,
        L"ServerIpAddress",
        WS_CHILD | WS_OVERLAPPED | WS_VISIBLE,
        MulDiv(LOWORD(units), 40, 4), 50,
        MulDiv(LOWORD(units), 70, 4),
        MulDiv(HIWORD(units), 11, 8),
        hwnd, NULL, NULL, NULL);

    // try to retrieve the control; does not work, returns null
    HWND wnd_server_ipaddress = FindWindowEx(hwnd, NULL, NULL, L"ServerIpAddress");

    DWORD err = GetLastError(); // --> returns 0

但是wnd_server_ipaddress 是 NULL。我正在对另外两个名称不同的标准编辑窗口做同样的事情，并且它正在工作。查看 Spy++ 以确保层次结构正确无误。调用后添加GetLastError()，返回0。

        // works
        HWND wnd_server_name = FindWindowEx(hwnd, NULL, NULL, L"ServerName");

        // does not work
        HWND wnd_server_ipaddress = FindWindowEx(hwnd, NULL, WC_IPADDRESS, L"ServerIpAddress");
        HWND wnd_server_ipaddress2 = FindWindow(WC_IPADDRESS, L"ServerIpAddress");

        // works
        wchar_t server_name[512] = { 0 };
        GetWindowText(wnd_server_name, server_name, 512);

        // does not work because wnd_server_ipaddress is null
        wchar_t server_ipaddress[16] = { 0 };
        DWORD dwAddr = 0x0;
        int iCount = (int)SendMessage(wnd_server_ipaddress, IPM_GETADDRESS, 0, (LPARAM)&dwAddr);
        _snwprintf_s(server_ipaddress, sizeof(server_ipaddress) / sizeof(*server_ipaddress), 16,
            L"%ld.%ld.%ld.%ld",
            (dwAddr >> 24) & 0xff,
            (dwAddr >> 16) & 0xff,
            (dwAddr >> 8)  & 0xff,
            (dwAddr)       & 0xff);

问题：是否有特定于 WC_IPADDRESS 的东西导致 FindWindowEx 找不到控件？

---

编辑 添加了适用于标准控件的代码。

    // creation with ServerName as lpWindowName
    HWND eName = CreateWindowW(L"Edit", L"ServerName",
        WS_CHILD | WS_VISIBLE | WS_BORDER,
        MulDiv(LOWORD(units), 40, 4), 10,
        MulDiv(LOWORD(units), 150, 4),
        MulDiv(HIWORD(units), 11, 8),
        hwnd, NULL, NULL, NULL);

    // reset text
    SetWindowText(eName, L"");

    // retrieve control - works
    HWND wnd_server_name = FindWindowEx(hwnd, NULL, NULL, L"ServerName");

    // retrieve value - works, gets whatever the text in the control is
    wchar_t server_name[512] = { 0 };
    GetWindowText(wnd_server_name, server_name, 512);

Answer 1

IP Address control 是 not a standard edit control。将"ServerIpAddress" 之类的窗口文本分配给 IP 地址控件是没有意义的，并且很可能在窗口创建过程中被丢弃。要将 IP 地址分配给 IP 地址控件，您必须使用 IPM_SETADDRESS 窗口消息。

另外，根据FindWindowEx() 文档：

如果lpszWindow参数不为NULL，FindWindowEx调用GetWindowText函数来检索窗口名称进行比较。

GetWindowText() 不适用于 IP 地址控件，就像它用于标准编辑控件一样。要从 IP 地址控件检索 IP 地址，您必须使用 IPM_GETADDRESS 窗口消息。

因此，当使用FindWindow/Ex() 时，无法通过其文本内容找到 IP 地址控件，就像标准编辑控件一样。它只能通过其WC_IPADDRESS 类名找到。

要执行您正在尝试的操作，您需要：

1. 保存CreateWindow()返回的IP地址控件的HWND（这是首选方案）：

   HWND gIpAddress; // stored somewhere that you can reach it
   
   ...
   
   // hwnd is the parent of the IP address window
   gIpAddress = CreateWindowW(WC_IPADDRESS,
       L"",
       WS_CHILD | WS_OVERLAPPED | WS_VISIBLE,
       MulDiv(LOWORD(units), 40, 4), 50,
       MulDiv(LOWORD(units), 70, 4),
       MulDiv(HIWORD(units), 11, 8),
       hwnd, NULL, NULL, NULL);
   
   ...
   
   DWORD dwAddr = 0x0;
   SendMessage(gIpAddress, IPM_GETADDRESS, 0, (LPARAM)&dwAddr);
   ...
   

2. 为IP地址控件指定一个控件ID（在CreateWindow()的hMenu参数中），然后使用GetDlgItem()获取IP地址控件的HWND时需要：

   // hwnd is the parent of the IP address window
   HWND eIPAddress = CreateWindowW(WC_IPADDRESS,
       L"",
       WS_CHILD | WS_OVERLAPPED | WS_VISIBLE,
       MulDiv(LOWORD(units), 40, 4), 50,
       MulDiv(LOWORD(units), 70, 4),
       MulDiv(HIWORD(units), 11, 8),
       hwnd, (HMENU)12345, NULL, NULL);
   
   ...
   
   // hwnd is the parent of the IP address window
   HWND wnd_server_ipaddress = GetDlgItem(hwnd, 12345);
   DWORD dwAddr = 0x0;
   SendMessage(wnd_server_ipaddress, IPM_GETADDRESS, 0, (LPARAM)&dwAddr);
   ...