////  RootViewController.m//  UITextField////  Created by YouXianMing on 14-9-15.//  Copyright (c) 2014年 YouXianMing. All rights reserved.//#import "RootViewController.h"@interface RootViewController ()<UITextFieldDelegate>@property (nonatomic, strong) UITextField *textField;@end@implementation RootViewController- (void)viewDidLoad{    [super viewDidLoad];    _textField                      = [[UITextField alloc] initWithFrame:CGRectMake(10,  80, 300, 40)];    _textField.layer.borderWidth    = 1.f;    _textField.layer.borderColor    = [UIColor redColor].CGColor;    _textField.backgroundColor      = [UIColor whiteColor];    _textField.textAlignment        = kCTTextAlignmentLeft;    // 左对齐    _textField.delegate             = self ;    _textField.keyboardType         = UIKeyboardTypeNumberPad; // 数字键盘    _textField.placeholder          = @"请输入4位验证码";    _textField.clearsOnBeginEditing = YES;                // 空出左侧边缘空隙（通过添加一个view来实现）    UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 10,                                                            CGRectGetHeight(_textField.bounds))];    _textField.leftView     = view;    _textField.leftViewMode = UITextFieldViewModeAlways;        [self.view addSubview:_textField];        // 添加手势    [self addGesture];}- (void)addGesture{    // 手势    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapGesture:)];    [self.view addGestureRecognizer:tap];}// 限制输入长度- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{    if (range.location >= 4)    {        return NO;    }    else    {        return YES;    }}- (void)tapGesture:(UITapGestureRecognizer *)tap{    // 取消第一响应状态    [_textField resignFirstResponder];}@end