iOS — is it possible to force a UILabel subclass object to become the first responder?

问题

Is there any way to do this?

I tried putting the following into the subclass:

- (BOOL)canBecomeFirstResponder 
{
    return YES;
}

But when I sent the object a becomeFirstResponder message, it still didn't become the first responder.

回答1:

Yes, it is possible. You should:

1. Override becomeFirstResponder to return YES.

2. Set userInteractionEnabled to YES.

3. Add a UITapGestureRecognizer to handle taps.

4. Call becomeFirstResponder from the tap handler.

You can even override inputView to get a input control at the bottom of the screen. Otherwise there will be nothing.

回答2:

I have no definite answer, just a few (maybe crazy) ideas: Have you also tried to override becomeFirstResponder to return YES? Does it have userInteractionEnabled also set to YES?

Otherwise, make it a custom UIButton instead of a custom UILabel...

回答3:

This worked for me.

Subclass UILabel and override these methods:

- (BOOL)canBecomeFirstResponder {
        return YES;
    }

    - (BOOL)canPerformAction:(SEL)action
                  withSender:(id)sender
    {
        return (action == @selector(copy:));
    }

    - (void)copy:(id)sender {
        [[UIPasteboard generalPasteboard] setString:self.text];
    }

Add Gesture to your label to detect tap.

UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(LongPressDetected:)];
[_messageLabel addGestureRecognizer:longPress];

Handle gesture event, present a UIMenuController with the desired frame:

- (void)LongPressDetected:(UILongPressGestureRecognizer*)gesture {

        [_messageLabel becomeFirstResponder];
        [[UIMenuController sharedMenuController] setTargetRect:_messageLabel.bounds inView:_messageLabel];
        [[UIMenuController sharedMenuController] setMenuVisible:YES animated:NO];
    }

来源：https://stackoverflow.com/questions/4089682/ios-is-it-possible-to-force-a-uilabel-subclass-object-to-become-the-first-res