FindFirstChangeNotification 两次通知更改 [英] FindFirstChangeNotification is notifying about changes twice

问题描述

我想监视文件系统中的文件夹.假设我想监视文件夹:C:\MyNewFolder

I want to monitor a folder in my file system. Let say I want to monitor the folder: C:\MyNewFolder

我有这个代码来做:

HANDLE  ChangeHandle=FindFirstChangeNotification(_T("C:\\\MyNewFolder"),FALSE,FILE_NOTIFY_CHANGE_LAST_WRITE);
for(;;)
{
    DWORD Wait=WaitForSingleObject(ChangeHandle,INFINITE);
    if (Wait == WAIT_OBJECT_0)
    {
        MessageBox(NULL,_T("Change"),_T("Change"),MB_OK);
        FindNextChangeNotification(ChangeHandle);
    }
    else
    {
        break;
    }
}

我想要一个消息框来通知我文件夹中的任何文件更改.该代码工作正常，但我有一个问题.问题是我每次更改都会收到 2 条通知.我的代码有什么问题?谢谢.

I want to have a messagebox that notifying me about any file change in my folder. That code works fine but I have one problem. The problem is that I got 2 notification for each change. What is the problem with my code? Thanks.

推荐答案

这完全正常.对文件的更改通常涉及对文件数据的更改以及对目录条目的更改.文件长度和最后写入日期等元数据属性存储在那里.因此，您会收到两者的通知.ReadDirectoryChangesW() 不区分两者.

This is entirely normal. A change to a file usually involves a change to the file data as well as a change to the directory entry. Metadata properties like the file length and the last write date are stored there. So you'll get a notification for both. ReadDirectoryChangesW() doesn't otherwise distinguish between the two.

这与对同一文件进行多次更改的过程没有什么不同.确保能够处理这两种情况.这通常涉及一个计时器，因此您不会在通知上执行的操作数量过多.通常还需要这样的计时器，因为正在更改文件的进程仍然对其进行了锁定，以防止您对文件进行任何操作.在进程关闭文件之前，不确定的时间之后.

This is not different from a process making multiple changes to the same file. Be sure to be able to handle both conditions. This usually involves a timer so you don't go overboard with the number of operations you perform on a notification. Such a timer is also often required because the process that is changing the file still has a lock on it that prevents you from doing anything with the file. Until the process closes the file, an indeterminate amount of time later.

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