mfc中postmessage和sendmessage

Question

我写个mfc程序，用对话框的edit box接受输入文字，然后点击idok，jl自定义消息到CMyView类处理函数，然后drawtext，用send没问题，用post点idok后程序崩溃

修改CTextDoc::OnGetText
   将原来的代码：
pView->SendMessage(WM_CHANGE_TEXT, 0, (LPARAM)&dlg.m_szText);
   修改为：
  pView->PostMessage(WM_CHANGE_TEXT, 0, (LPARAM)&dlg.m_szText);

 

void CTextDoc::OnGetText()

{

        // TODO: Add your command handler code here

        CTextDlg dlg;

        if(dlg.DoModal() == IDOK)

        {

                POSITION pos = GetFirstViewPosition();

                CView *pView = GetNextView(pos);

                ASSERT_VALID(pView);

/////////////////////////////////////////////////////

                pView->SendMessage(WM_CHANGE_TEXT, 0, (LPARAM)&dlg.m_szText);

/////////////////////////////////////////////////////

                UpdateAllViews(NULL);

        }

}

Answer 1

在哪一行崩溃？

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Visual C++ MVP

Answer 2

自己思考，问题已解决：postmessage是立即返回（without waiting the completion of message handler possessing ）

OnGetText()随之结束，但是

等到handler响应WM_CHANGE_TEXT时，所传(LPARAM)&dlg.m_szText的内存或者说是dlg已经归还，所以会有访问越界程序崩溃

版主看我说的对不

Answer 3

是，如果你要传地址的话，传一个生存期比较久一点的变量的地址。

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Answer 4

如果我这样改，然后在OnChangeText(wparam,lparam)中delete (CTextDlg*) lparam，会有什么问题

（实验后发现OnChangeText未能响应，消息跑到哪去了？）void CHellosDoc::OnGetText()
{
// TODO: Add your command handler code here
CTextDlg *pdlg=new CTextDlg;
   if(pdlg->DoModal() == IDOK)
  {
          ::PostMessage(pdlg->GetSafeHwnd(),WM_CHANGE_TEXT,  0,  (LPARAM)pdlg);
    UpdateAllViews(NULL);
  }
}

Answer 5

不知道你传一个对话框的地址做什么，这个对话框又没数据。PostMessage到这个对话框没用，对话框还没有窗口句柄，收不到信息的。看你的需求似乎一个非模态对话框就可以了，不用线程？

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Answer 6

永远不要把资源在线程中传来传去，要使用句柄，然后通过句柄向资源所在的线程发送消息。哪个线程的动作就在哪个线程执行。另外你的这个例子，可以在 if(pdlg->DoModal() == IDOK)中做个小戏循环，等待一个Event然后在OnChangeText执行结束时SetEvent就行了。

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麻烦把正确答案设为解答。