1 - (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{ 2      3     if ([text isEqualToString:@"\n"]){ 4         [self onSendBarrage:nil]; 5         return YES; 6     } 7     NSMutableAttributedString *attrM = [[NSMutableAttributedString alloc]initWithAttributedString:textView.attributedText]; 8     if (textView == self.textFieldBarrage) 9     {10         if (attrM.length > MAX_INPUT_LEN) {11             NSRange range = NSMakeRange(0, MAX_INPUT_LEN);12             textView.attributedText = [attrM attributedSubstringFromRange:range];13         }14         [self fixChatButtonStateWithTextViewLength:attrM.length];15     }16     return YES;17 }

以上代码的好处主要在于,先提前计算用户输入的内容,再根据推断出的输入框结果,对输入框的字符进行截取.