UItextfield 动态限制输入的字数

@property (nonatomic, strong) UITextField *txtName;

- (void)viewDidLoad {

    [super viewDidLoad];

//UIControlEventEditingChanged(包括中文和英文等输入法)

[self.txtName addTarget:self action:@selector(limitLength:) forControlEvents:UIControlEventEditingChanged];

}

//包括中文和英文等输入法判断，不然会因为联想记忆而崩溃

-(void)limitLength:(UITextField *)sender

{

    bool isChinese;//判断当前输入法是否是中文

    if ([[[UITextInputMode currentInputMode] primaryLanguage] isEqualToString: @"en-US"]) {

        isChinese = false;

    }

    else

    {

        isChinese = true;

    }

     

    if(sender == self.txtName) {

        // 8位

        NSString *str = [[self.txtName text] stringByReplacingOccurrencesOfString:@"?" withString:@""];

        if (isChinese) { //中文输入法下

                UITextRange *selectedRange = [self.txtName markedTextRange];

                //获取高亮部分

                UITextPosition *position = [self.txtName 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) {

                    NSLog(@"汉字");

                    if ( str.length>=9) {

                        NSString *strNew = [NSString stringWithString:str];

                        [self.txtName setText:[strNew substringToIndex:8]];

                    }

                }

                else

                {

                    NSLog(@"输入的英文还没有转化为汉字的状态");

                 

                }

        }else{

            NSLog(@"str=%@; 本次长度=%d",str,[str length]);

            if ([str length]>=9) {

                NSString *strNew = [NSString stringWithString:str];

                [self.txtName setText:[strNew substringToIndex:8]];

            }

        }

    }

}