textField限制只能输入一定长度的字符

2015/11/05 38015

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- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string;
{  //string就是此时输入的那个字符textField就是此时正在输入的那个输入框返回YES就是可以改变输入框的值NO相反
 
if ([string isEqualToString:@"\\n"])  //按会车可以改变
    {
        return YES;
    }
 
    NSString * toBeString = [textField.text stringByReplacingCharactersInRange:range withString:string]; //得到输入框的内容
 
    if (self.myTextField == textField)  //判断是否时我们想要限定的那个输入框
    {
        if ([toBeString length] > 20) { //如果输入框内容大于20则弹出警告
            textField.text = [toBeString substringToIndex:20];
            UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:nil message:@"超过最大字数不能输入了" delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil] autorelease];
            [alert show];
            return NO;
        }
    }
    return YES;
}