uialertview 设置输入的位数限制

-(void)creatalter{

    UIAlertView *alertview = [[UIAlertViewalloc]initWithTitle:@"请输入登录密码"message:nildelegate:selfcancelButtonTitle:@"取消"otherButtonTitles:@"确定",nil];

    alertview.alertViewStyle =UIAlertViewStylePlainTextInput;

    alertview.tag =826;

   UITextField * textfield=(UITextField *) [alertviewtextFieldAtIndex:0];

    textfield.tag=1200;

    textfield.delegate =self;

    [alertview show];

}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string;

{

 

    if ([stringisEqualToString:@"\n"])

    {

        returnYES;

    }

    NSString * toBeString = [textField.textstringByReplacingCharactersInRange:rangewithString:string];

    

    if (textField.tag==1200)

    {

        if ([toBeStringlength] >16) { //这里限定输入的位数

            textField.text = [toBeStringsubstringToIndex:16];

            

            returnNO;

        }

    }

    returnYES;

}