I have added an OnPaint() function to my dialog class but its not getting called after dlg.DoModal()

问题

Can anyone please help me understand how to override OnPaint() for a dialog class derived from CDialog.

Here is the code:

ColorImageDlg *pDlg = NULL;
pDlg = new ColorImageDlg;
pDlg->DoModal();
delete pDlg;

I'm overriding OnInitDialog() and it's getting called. But while overriding OnPaint() it is not getting called.

Can any one please help me fixing it?

回答1:

First of all what is the point of creating the instance of the dialog on heap? You can simply do:

ColorImageDlg dlg;
dlg.DoModal(); 

You need to modify your message map like this:

BEGIN_MESSAGE_MAP(ColorImageDlg, CDialog)
    ON_WM_PAINT()
END_MESSAGE_MAP()

Use VS Class Wizard to avoid problems like that.

回答2:

If you can't use the ClassWizard then there is another way. Here is a resource about it:

(VS2015 version) https://msdn.microsoft.com/en-us/library/dey7ke4c.aspx

(VS2008 version) https://msdn.microsoft.com/en-us/library/dey7ke4c(v=vs.90).aspx)

But basically, once you have defined the dialog resource and attached it to a new class, make sure the Class View tab is selected:

Next, make sure your dialog class is selected in the class view:

Then, click on the Messages icon of the Properties panel:

Scroll down the list of messages and locate WM_PAINT. Then click the dropdown arrow and select the option to add it:

As you can see, it has inserted all the needed code:

Hope this helps.

来源：https://stackoverflow.com/questions/37722069/i-have-added-an-onpaint-function-to-my-dialog-class-but-its-not-getting-called