UITextField使用的一些细节

//
//  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