我有一个用 C 语言(使用 gcc/MinGW)编写的 Windows 应用程序，除了一些 UI 问题外，它运行良好。第一，我根本无法让进度条从线程更新。事实上，我可能无法更新任何 UI 内容。

基本上，我有一个执行某些处理的派生线程，我尝试从该线程更新主线程中的进度条。我通过对主 hwnd 使用 PostMessage() 来尝试这个，但没有运气，即使我可以做其他事情，比如打开消息框。但是，不清楚消息框是在线程内还是在主线程上被调用。

这是一些代码:

// in header/globally accessible
HWND wnd; // main application window
HWND progress_bar; //progress bar

typedef struct { //to pass to thread
    DWORD mainThreadId;
    HWND mainHwnd;
    char *filename;
} THREADSTUFF;


//callback function
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam){
    switch (msg){
        case WM_CREATE:{
            // create progress bar
            progress_bar = CreateWindowEx(
                0,
                PROGRESS_CLASS,
                (LPCTSTR) NULL,
                WS_CHILD | WS_VISIBLE,
                79,164,455,15,
                hwnd,
                (HMENU)20,
                NULL,
                NULL);

            SendMessage(progress_bar, PBM_SETSTEP, 1, 0 );
            SendMessage(progress_bar, PBM_SETPOS, 0, 0 );
            //test to make sure it actually works
            SendMessage(progress_bar, PBM_STEPIT, 0, 0 ); //works fine
            SendMessage(progress_bar, PBM_STEPIT, 0, 0 ); //works fine
            SendMessage(progress_bar, PBM_STEPIT, 0, 0 ); //works fine
            SendMessage(progress_bar, PBM_STEPIT, 0, 0 ); //works fine

            break;
        }

        case WM_COMMAND: {
            if(LOWORD(wParam)==2){ //do some processing in a thread

                //struct of stuff I need to pass to thread
                THREADSTUFF *threadStuff;
                threadStuff = (THREADSTUFF*)malloc(sizeof(*threadStuff));
                threadStuff->mainThreadId = GetCurrentThreadId();
                threadStuff->mainHwnd = hwnd;
                threadStuff->filename = (void*)&filename;
                hThread1 = CreateThread(NULL,0,convertFile (LPVOID)threadStuff,0,NULL);

            }else if(LOWORD(wParam)==5){ //update progress bar

                MessageBox(hwnd,"I got a message!", "Message",  MB_OK | MB_ICONINFORMATION);
                PostMessage(progress_bar,PBM_STEPIT,0,0);
            }
            break;
        }
    }
}

这一切似乎都正常。问题出在线程中:

DWORD WINAPI convertFile(LPVOID params){

    //get passed params, this works perfectly fine
    THREADSTUFF *tData = (THREADSTUFF*)params;

    MessageBox(tData->mainHwnd,tData->filename,"File name",MB_OK | MB_ICONINFORMATION); //yep

    PostMessage(tData->mainHwnd,WM_COMMAND,5,0); //only shows message
    PostThreadMessage(tData->mainThreadId,WM_COMMAND,5,0); //does nothing
}

当我说“只显示消息”时，这意味着回调中的 MessageBox() 函数有效，但 PostMessage() 函数无法更新进度条的位置。

如果我使用 PostThreadMessage() 向主线程的消息循环发送消息，我可以拦截它并启动 MessageBoxes，因此它肯定可以正常工作。但是，即使我尝试以这种方式更新进度条。它仍然不会更新。

我错过了什么？

最佳答案

来自MSDN documentation for PBM_STEPIT :

wParam
    Must be zero.
lParam
    Must be zero.

CLR_DEFAULT 定义为 0xFF000000L。如果您将代码更改为:

PostMessage(progress_bar, PBM_STEPIT, 0, 0);

关于windows - 无论如何，我无法让这个进度条从线程更新，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/4496789/