发送 WM_SETTEXT 时如何避免 EN_CHANGE 通知? [英] How to avoid EN_CHANGE notifications when sending WM_SETTEXT?

问题描述

我有一个 CEdit 派生控件，当 undelying 数据为空时，它显示字符串N/A".我最近添加了代码来清空控件 (SetWindowText("");) 当它获得焦点并在焦点丢失时设置如果回到 "N/A"(SetWindowText("N/A")) 如果用户离开控制空.

I have a CEdit derived control that displays the string "N/A" when the undelying data is null. I recently added code to empty the control(SetWindowText("");) when it gains focus and set if back to "N/A"(SetWindowText("N/A")) when the focus is lost if the user left the control empty.

唯一的问题是将窗口文本设置为 "" 或 "N/A" 会触发 EN_CHANGE，因此我的对话框认为数据已更改.

The only problem is that setting the window text to "" or "N/A" triggers EN_CHANGE, so my dialog thinks that the data has changed.

如何避免在调用 SetWindowText (WM_SETTEXT) 时触发 EN_CHANGE?

How can I avoid EN_CHANGE from being fired when calling SetWindowText (WM_SETTEXT)?

注意事项

-我知道我可以将编辑控件设置为 Multiline=TRUE 但这对我来说是不可接受的.

-I know I can set the edit control to Multiline=TRUE but that's not accpectable for me.

-我的应用程序是 MBCS 所以我不能使用 SetCueBanner

-My application is MBCS so I can't use SetCueBanner

-我想要一个优雅的解决方案.暂时将父窗口设置为 NULL 不是一个优雅的解决方案.

-I want an elegant solution. Setting the parent window to NULL temporarily is not an elegant solution.

-我希望解决方案在我的自定义控件中，而不是在每个对话框中

-I want the solution to be in my custom control, not in each dialog

谢谢

推荐答案

我终于找到了适合我的问题的解决方案.

I finally found a suitable solution to my problem.

首先，我在派生控件的头文件中添加了一个标志，并在构造函数中将其初始化为 false

First, I added a flag to my derived control's header file and I initialized it to false in the constructor

bool m_bNoEnChange;

<小时>

我在派生控件的头文件中覆盖了 OnChildNotify，并且在实现中，我使用 EN_CHANGE 参数检查了 WM_COMMAND 消息.然后我返回 TRUE 以防止将消息发送到父级(对话框/页面)

---

I overrode the OnChildNotify in my derived control's header file and in the implementation, I checked for the WM_COMMAND message with the EN_CHANGE parameter. I then returned TRUE to prevent the message from being sent to the parent(dialog/page)

virtual BOOL OnChildNotify(UINT message, WPARAM wParam, LPARAM lParam, LRESULT* pLResult);

<小时>

BOOL CADEdit::OnChildNotify(UINT message, WPARAM wParam, LPARAM lParam, LRESULT* pLResult) 
{
    if(message == WM_COMMAND && HIWORD(wParam) == EN_CHANGE)
    {
        //If the flag is set, don't send the message to the parent window
        if(m_bNoEnChange)
            return TRUE;
    }

    return CEdit::OnChildNotify(message, wParam, lParam, pLResult);
}

<小时>

最后，当控件获得和失去焦点时，我用我的标志包裹了有问题的 SetWindowText

---

Finally, when the control gains and loses focus, I wrapped the problematic SetWindowText with my flag

m_bNoEnChange = true;
SetWindowText(_T(""));
m_bNoEnChange = false;

<小时>

这个解决方案对我来说是最好的，因为我不必修改每个对话框.

---

This solution is the best in my case because I don't have to modify each dialog.

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