Posted on 2006-07-21 09:50
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Win32
SendMessageTimeout并不是簡(jiǎn)單在SendMessage加上Timeout的功能。
MSDN上面有一段文字是這樣說(shuō)的
If the specified window was created by the calling thread, the window procedure is called immediately as a subroutine. If the specified window was created by a different thread, the system switches to that thread and calls the appropriate window procedure. Messages sent between threads are processed only when the receiving thread executes message retrieval code. The sending thread is blocked until the receiving thread processes the message. However, the sending thread will process incoming nonqueued messages while waiting for its message to be processed. To prevent this, use SendMessageTimeout with SMTO_BLOCK set. For more information on nonqueued messages, see Nonqueued Messages.
翻譯一下：
SendMessage : 如果指定窗口由調(diào)用線程創(chuàng)建，那么窗口過(guò)程會(huì)被當(dāng)成一個(gè)子程序立即調(diào)用。如果指定窗口由另外一個(gè)線程創(chuàng)建，那么系統(tǒng)會(huì)切換到那個(gè)線程，并且調(diào)用合適的窗口過(guò)程。在線程之間傳遞的消息僅僅當(dāng)接收線程執(zhí)行message retrieval code才會(huì)被處理。發(fā)送線程會(huì)被堵塞直到接收線程處理完消息。但是，發(fā)送線程在等待的同時(shí)會(huì)處理收到的nonqueued messages 。為了阻止這一點(diǎn)，使用帶有SMTO_BLOCK參數(shù) 的SendMessageTimeout .
=================================華麗的分割線===========================
我曾經(jīng)遇到這個(gè)問(wèn)題，我調(diào)用SendMessage向另外一個(gè)線程窗口發(fā)message，本來(lái)以為他會(huì)一直block住，但是他卻調(diào)用了另外一個(gè)消息的處理程序，導(dǎo)致了行為不正確。所以一定要小心使用SendMessage發(fā)給其他線程的窗口。
我修改了一下，把
pWnd->SendMessage(MSG_LOG_MESSAGE, nMsgType, (LPARAM)(LPCTSTR)m_cstrMessage);
改成了
HWND hWnd = pWnd->GetSafeHwnd();
::SendMessageTimeout(hWnd,MSG_LOG_MESSAGE, nMsgType, (LPARAM)(LPCTSTR)m_cstrMessage,SMTO_BLOCK,15000,0);
解決了這個(gè)bug.
Feedback
# re: SendMessage 和 SendMessageTimeout 回復(fù) 更多評(píng)論
2006-12-27 15:02 by
好!!!雖然我看不懂寫(xiě)些什么
# re: SendMessage 和 SendMessageTimeout 回復(fù) 更多評(píng)論
2009-02-12 14:50 by
沒(méi)看明白啊。。。可能是我水平不夠。。。
# re: SendMessage 和 SendMessageTimeout 回復(fù) 更多評(píng)論
2011-11-17 10:56 by
哥也沒(méi)看懂呀！！！
# re: SendMessage 和 SendMessageTimeout 回復(fù) 更多評(píng)論
2012-02-20 15:59 by
首先英文翻譯的的比較準(zhǔn)確、專業(yè)！
正在研究SendMessage和SendMessageTImeOut區(qū)別，其中一個(gè)例子是，啟動(dòng)應(yīng)用程序新實(shí)例前，向已存在的實(shí)例發(fā)送copydata消息做一些處理，原先用的是sendmessage，現(xiàn)在覺(jué)得用sendmessagetimeout應(yīng)該更穩(wěn)妥一些
# re: SendMessage 和 SendMessageTimeout 回復(fù) 更多評(píng)論
2012-02-20 16:21 by
LRESULT SendMessageTimeout(
HWND hWnd, // handle to window
UINT Msg, // message
WPARAM wParam, // first message parameter
LPARAM lParam, // second message parameter
UINT fuFlags, // send options
UINT uTimeout, // time-out duration
PDWORD_PTR lpdwResult // return value for synchronous call
);
fuFlags
[in] Specifies how to send the message. This parameter can be one or more of the following values
SMTO_ABORTIFHUNG
Returns without waiting for the time-out period to elapse if the receiving process appears to be in a "hung" state.
順便翻譯一下最后一句
“如果接收進(jìn)程處于掛起狀態(tài)，不再等待（超時(shí)）直接返回”