如何限制UITextView iOS中的字符

Question

我有一个UITextView,我想限制用户可以输入的字符数.如果文本字段为空但我没有运气,我也试图显示警告.

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];
        }
}

这是文本限制方法似乎不起作用,

- (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);
}
}

Answer 1

1)像这样在你的viewcontroller中添加UITextViewDelegate

@interface ViewController : UIViewController <UITextViewDelegate>

每次用户在键盘上键入字符时,就在显示字符之前,调用以下方法.这是一个方便的位置,用于测试用户正在键入的字符,并禁止您要限制的特定字符.

TextView中:shouldChangeCharactersInRange:replacementString

2)然后编写以下代码.而不是140你可以把你想要的任何数字.

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

有关更多帮助,请查看UItextView

Swift 2.0解决方案

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