键盘相关处理

实际开发中在退出当前界面前，要将弹起的键盘收起

 - (void)viewWillDisappear:(BOOL)animated {    
      [super viewWillDisappear:animated];
      
      // 视图退出编辑状态（收起键盘）
      [self.view endEditing:YES];
 }

如果当前控制器是TableViewController时，就不能这么写了

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
    
    // 关闭第一响应者（收起键盘）
    [self.textField resignFirstResponder];
}

在实际开发中有时候需要对 文本输入框UITextfiled 进行一些限制.
比如说在输入金额的时候我们希望只能输入最多两位小数.应该怎么办呢?UITextfiled 有个代理方法

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string; // return NO to not change text

官方的注释是** return NO 的时候是不能改变文字的.那么我们就在这个方法里做手脚.为了少做一些判断.我们可以先限制调出的键盘类型为UIKeyboardTypeDecimalPad.

UIKeyboardTypeDecimalPad

// 输入金额 限制两个小数

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
      if ([textField.text containsString:@"."]) {
        if ([string isEqualToString:@"."]) return NO;
        NSRange rangeOfPoint = [textField.text rangeOfString:@"."];
        if (range.location > rangeOfPoint.location + 2) return NO;
      }
        return YES;
      }

附录: 键盘样式:

UIKeyboardTypeDefault

UIKeyboardTypeASCIICapable

UIKeyboardTypeNumbersAndPunctuation

UIKeyboardTypeURL

UIKeyboardTypeNumberPad

UIKeyboardTypePhonePad电话号码键盘

UIKeyboardTypeNamePhonePad

UIKeyboardTypeEmailAddress

UIKeyboardTypeDecimalPad金额键盘

UIKeyboardTypeTwitter

UIKeyboardTypeWebSearch

UIKeyboardTypeAlphabet = UIKeyboardTypeASCIICapable