文本框文字长度限制

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text;

方法中参数理解

textView：文本框

range：输入文字所要替换位置和长度

text:替换文字内容

 

限制文本输入字数为10，判断逻辑是：中文状态下，每个汉字和符号都算一个字，在英文状态下，字母和符号都算半个字。针对这个来检查看看是否不符合条件，给出警告。符合条件的时候就发送。

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text {
    float sum = 0.0;
    for(int i=0;i<[textView.text length];i++) {
        NSString *character = [textView.text substringWithRange:NSMakeRange(i, 1)];
        if([character lengthOfBytesUsingEncoding:NSUTF8StringEncoding] == 3) {
            sum++;
        }
        else {
            sum += 0.5;
        }
    }
    int bys = (int)(ceil(sum));
    if (bys > =10) {
       UIAlertView *alertView =[[UIAlertView alloc] initWithTitle:@""  message:@"输入的文字超过10位" delegate:self cancelButtonTitle:@"" otherButtonTitles:nil];
       [alert show];
       [alert release];
       NSTimer showTimer = [NSTimer scheduledTimerWithTimeInterval:1.5 target:self selector:@selector(hideAlertView:) userInfo:alertView repeats:NO];
    }
    return (bys >= 10) ? NO:YES;
}

- (void)hideAlertView:(NSTimer)timer {
   UIAlertView *alertView = timer.userInfo;
   [alertView dismissWithClickedButtonIndex:0 animated:YES];
}