How to limit characters in UITextView iOS

问题:

I have a UITextView and i would like to limit the number of characters a user can input. i have also tried to display a warning if the textfield is empty but to no luck.

textview.h

@property (nonatomic,strong) IBOutlet UITextView *textField;
@property (nonatomic, retain) NSString *userText;

textview.m

- (IBAction)next:(id)sender {

    self.userText = self.textField.text;

    if ([self.textField.text length] == 0) {
            UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Error!"
                                                                message:@"Enter some text"
                                                               delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
            [alertView show];
        }
}

here is the text limit method that does not seem to work,

- (BOOL)textView:(UITextView *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{

    if(range.length + range.location > textField.text.length)
    {
        return NO;

    } else {

    NSUInteger newLength = [textField.text length] + [string length] - range.length;
    return newLength <= 70;
    return (textField.text.length <= 70);
}
}

回答1:

1) add UITextViewDelegate in your viewcontroller like this

@interface ViewController : UIViewController <UITextViewDelegate>

Each time a user types a character on the keyboard, just before the character is displayed,following method get called. This is a handy location to test the characters that a user is typing and disallow specific characters you want to restrict.

textView:shouldChangeCharactersInRange:replacementString

2) then write following code. instead of 140 you can put whatever number you want.

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
    return textView.text.length + (text.length - range.length) <= 140;
}

For more help take a look at UItextView

Swift 2.0 solution

 func textView(textView: UITextView, shouldChangeTextInRange range: NSRange, replacementText text: String) -> Bool {
    return textView.text.characters.count + (text.characters.count - range.length) <= textViewLimit
}

回答2:

Try this

 - (BOOL)isAcceptableTextLength:(NSUInteger)length {
    return length <= 70;
}

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)string {
    return [self isAcceptableTextLength:textField.text.length + string.length - range.length];
}

-(IBAction)checkIfCorrectLength:(id)sender{
    if (![self isAcceptableTextLength:self.textField.text.length]) {
        // do something to make text shorter
    }
}

回答3:

you can use below code to restrict textview characters in first method you can set restricted length for textfield or if you past text which is more than your restricted text it will create substring of that string to fix length for textview.

#pragma mark - Textview Delegate
 -(void)textViewDidChange:(UITextView *)textView
 {   
    NSString *temp = textView.text;
   titleLength = textView.text.length;
   if (titleLength > RESTRICTED_LENGHT ) 
    {
    textView.text = [temp substringToIndex:RESTRICTED_LENGHT];
    }
 }

or you can use this delegate method and return No if text view text length is greater than your restricted length.

 - (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
     if([text length] == 0)
      {
        if([textView.text length] != 0)
        {
          return YES;
        }
     }
   else if([[textView text] length] > 139)
    {
       return NO;
    }
   return YES;
}