页面启动时添加通知
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textViewChange:) name:@"UITextViewTextDidChangeNotification" object:self.txtSuggestion];
 
 
 
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
    NSString *toBeString = [textView.text stringByReplacingCharactersInRange:range withString:text];
    if (toBeString.length > kMaxLength && range.length!=1){
        textView.text = [toBeString substringToIndex:kMaxLength];
        return NO;
    }
    return YES;
}
 
-(void)textViewChange:(NSNotification *)obj{
    UITextField *textField = (UITextField *)obj.object;
     
    NSString *toBeString = textField.text;
    NSString *lang = [[UIApplication sharedApplication]textInputMode].primaryLanguage; // 键盘输入模式
    if ([lang isEqualToString:@"zh-Hans"]) { // 简体中文输入，包括简体拼音，健体五笔，简体手写
        UITextRange *selectedRange = [textField markedTextRange];
        //获取高亮部分
        UITextPosition *position = [textField positionFromPosition:selectedRange.start offset:0];
        // 没有高亮选择的字，则对已输入的文字进行字数统计和限制
        if (!position) {
            if (toBeString.length > kMaxLength) {
                textField.text = [toBeString substringToIndex:kMaxLength];
            }
        }
        // 有高亮选择的字符串，则暂不对文字进行统计和限制
        else{
             
        }
    }
    // 中文输入法以外的直接对其统计限制即可，不考虑其他语种情况
    else{
        if (toBeString.length > kMaxLength) {
            textField.text = [toBeString substringToIndex:kMaxLength];
        }  
    }  
}
 
 
离开页面时
[[NSNotificationCenter defaultCenter]removeObserver:self name:@"UITextFieldTextDidChangeNotification"  
object:self.txtSuggestion];