OC - UITextField设置和键盘

导读：

• 一、创建UITextField
• 二、设置UITextField的leftView/rightView
• 三、UITextField的常用设置
• 四、键盘回收
• 五、键盘通知

一、创建UITextField

• UITextField 是UIControl的子类，UIControl又是UIView的子类，所以也是一个视图，只不过比UIView多了两个功能:1.文字显示，2.文本编辑。

UITextField *text = [[UITextField alloc] int];
text.frame = CGRectMake(50, 50, 180, 50)]; 
text.backgroundColor = [UIColor yellowColor]; 
[self.view addSubview:text]; 

二、设置UITextField的leftView/rightView

UIImageView *leftView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"icon"]];
leftView.frame = CGRectMake(0, 0, 55, 20);
leftView.contentMode = UIViewContentModeCenter;
self.textField.leftViewMode = UITextFieldViewModeAlways;
self.textField.leftView = leftView;

三、UITextField的常用设置

• UITextField不支持文字换行
• 设置text右侧清除按钮
  self.textField.clearButtonMode = UITextFieldViewModeAlways;
• 设置text的边框样式(圆角)
  text.borderStyle = UITextBorderStyleRoundedRect;
• 设置text默认显示文字(但是不作为文本内容的一部分)
  text.placeholder = @"请输入用户名";
• 设置text文字
  text.text = @"什么破烂”;
• 设置文本颜色
  text.textColor = [UIColor blackColor];
• 设置文本的对齐方式
  text.textAlignment = NSTextAlignmentCenter;
• 设置文字字体
  text.font = [UIFont systemFontOfSize:18];
• 设置输入框是否可编辑
  text.enabled = YES;
• 设置当开始编辑时,是否清除框中内容
  text.clearsOnBeginEditing = YES;
• 设置密码格式(输入框中内容是否以点的形式显示)
  text.secureTextEntry = YES;
• 设置弹出键盘的样式(数字键盘)
  text.keyboardType = UIKeyboardTypeNumberPad;
• 键盘右下角显示样式
  text.returnKeyType = UIReturnKeyGo;
• 设置tag值
  text.tag = 120;

三、键盘回收

• 点击右下角或者回车回收键盘
  1. 遵守协议：@interface ViewController ()<UITextFieldDelegate>
  2. 设置代理：text.delegate = self；
  3. 实现协议中的方法：
  - (BOOL)textFieldShouldReturn:(UITextField *)textField {
  [textField resignFirstResponder];
  return YES;
  }
• 点击空白处回收键盘
  - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
  {
  [self.textField resignFirstResponder];
  }

四、键盘通知

• //在view即将显示时添加对系统发出的键盘通知的监听 
  - (void)viewWillAppear:(BOOL)animated
  {
      [super viewWillAppear:animated];
  //为当前控制器注册键盘弹起和关闭通知
      [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(openKeyboard:) name:UIKeyboardWillShowNotification object:nil];
      [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(closeKeyboard:) name:UIKeyboardWillHideNotification object:nil];
  }
  /** 在view即将消失时取消键盘通知的监听 */
  - (void)viewWillDisappear:(BOOL)animated
  {
      [super viewWillDisappear:animated];
      [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
      [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillHideNotification object:nil];
  }
  /** 键盘弹起事件 */
  - (void)openKeyboard:(NSNotification *)notification
  {
        NSLog(@"%@",notification.userInfo);
  }
  /** 键盘关闭事件 */
  -(void)closeKeyboard:(NSNotification *)notification
  {
        NSLog(@"关闭了键盘");
  }
  /** 点击空白处回收键盘 */
  - (void)touchesBegan:(NSSet<UITouch *> *)touches   withEvent:(UIEvent *)event
  {
        [self.view endEditing:YES];
  }
  /** 销毁通知 */
  - (void)dealloc
  {
        [[NSNotificationCenter defaultCenter] removeObserver:self];
  }