How can I detect that a user has tapped a formatting button in a UIMenuController?

问题

My app allows users to format text in a UITextView by using some custom formatting buttons I've created. Now I want to enable the allowsEditingTextAttributes property of the text view so that users can copy and paste formatted text between text views. This enables the bold/italic/underline buttons in the standard UIMenuController for the text view. This is fine, but when users change the formatting through this menu, I need to call my custom method that updates the state of my custom formatting buttons. How can I detect that a user has tapped one of the UIMenuController's formatting buttons?

I looked for notifications in the UITextView and UIMenuController class references, but didn't see anything relevant. These formatting buttons don't trigger a UITextViewTextDidChangeNotification and don't trigger the textViewDidChange: method of the UITextViewDelegate. I also tried subclassing the UITextView class to override a method there, but I don't know what method to override. It looks like a bold: method doesn't exist, for example, even though a paste: method does exist there. Does anyone know what method of what class is called when tapping one of the bold/italic/underline buttons?

These buttons aren't mentioned in the Text Programming Guide for iOS or the UIMenuController class reference, as far as I can tell.

回答1:

This might be more helpful.

If you implement this method in UITextView subclass then you can control whether the menu options display or not. You can also check the log output to see what methods are getting called. In the example below I am disabling the text style options menu.

- (BOOL)canPerformAction:(SEL)action withSender:(id)sender {
    LOG(@"canPerformAction: called");
    FLOG(@" action %@", NSStringFromSelector(action));

    if (action == @selector(_showTextStyleOptions:)) {

                return NO;

    }

    return [super canPerformAction:action withSender:sender];
}

These are some of the selectors that get checked:

copy:
select:
selectAll:
paste:
delete:
_promptForReplace:
_showTextStyleOptions:  ***
_define:
etc...

If you select the Text Style Options menu then you get the following:

toggleBoldface:
toggleItalics:
toggleUnderline:

Hope this helps.

来源：https://stackoverflow.com/questions/20223966/how-can-i-detect-that-a-user-has-tapped-a-formatting-button-in-a-uimenucontrolle