问题
I have a UITextField set up to show a number pad. How do I require the user to enter exactly 5 digits?
I poked around and saw I should use shouldChangeCharactersInRange but I'm not quite understanding how to implement that.
回答1:
I'd just use this when the user leaves the textfield/validates with a button
if ([myTextField.text length] != 5){
//Show alert or some other warning, like a red text
}else{
//Authorized text, proceed with whatever you are doing
}
Now if you want to count the chars WHILE the user is typing, you might use in viewDidLoad
[myTextfield addTarget: self action@selector(textfieldDidChange:) forControlEvents:UIControlEventsEditingChanged]
-(void)textFieldDidChange:(UITextField*)theTextField{
//This happens every time the textfield changes
}
Please make sure to ask questions in the comments if you need more help :)
回答2:
Make yourself a delegate of UITextFieldDelegate and implement the following:
- (BOOL)textField:(UITextField *) textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSUInteger oldLength = [textField.text length];
NSUInteger replacementLength = [string length];
NSUInteger rangeLength = range.length;
NSUInteger newLength = oldLength - rangeLength + replacementLength;
BOOL returnKey = [string rangeOfString: @"\n"].location != NSNotFound;
//desired length less than or equal to 5
return newLength <= 5 || returnKey;
}
回答3:
- (BOOL) textField: (UITextField *)textField shouldChangeCharactersInRange: (NSRange)range replacementString: (NSString *)string {
NSString *newText = [textField.text stringByReplacingCharactersInRange: range withString: string];
return [self validateText: newText]; // Return YES if newText is acceptable
}
来源：https://stackoverflow.com/questions/27840460/require-a-uitextfield-to-take-5-digits