How to detect UIKeyboard “backspace” button touch

问题:

This question already has an answer here:

• Detect backspace in empty UITextField 23 answers

How can i detect backspace button pressed on UIKeyboard?

thanks

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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;
}

回答3:

Temporary i'm inserting a zero space char on textFieldDidBeginEditing

textField.text = @"\u200B";

on backspace, it remove that chars, but graphically it's the same!

It's an hack, it works, but it hide placeholder text... not good...