How to detect UIKeyboard “backspace” button touch on UITextField? [duplicate]

问题

How can i detect backspace button pressed on UIKeyboard?

thanks

EDIT: Is there any keyboard delegate that returns key pressed value?

回答1:

if the UITextField is empty, the shouldChangeTextInRange delegate method is not called You can subclass UITextField and override this method:

-(void)deleteBackward;
{
    [super deleteBackward];
    NSLog(@"BackSpace Detected");
}

since UITextField is compliant to the UITextInput protocol, this method is implemented, and you can override it to detect when backspace is pressed. Then, you can write your own protocol/delegate method to alert your custom textfield delegate if the backspace is detected.

回答2:

First of all your UIViewController that references the UITextField needs to conform to the UITextFieldDelegate protocol. Then set your class as delegate to the UITextField (eg. [myTextField setDelegate:self] ). Then in your class you add the following. When a string of "" is sent as the replacementString you know it's backspace.

(BOOL)textField:(UITextField *)textField 
      shouldChangeCharactersInRange:(NSRange)range 
      replacementString:(NSString *)string
{                
    if ([string isEqualToString:@""]) {
        NSLog(@"Backspace");            
    }
    return YES;
}