使不可响应事件的UILabel响应事件

使不可响应事件的UILabel响应事件

• 说明：响应的结果为弹出对话框通知

1. 新建一个继承自UILabel的类，暂且为EventableLabel

2. 在EventableLabel.m中，需要添加的方法有

• - (BOOL)canBecomeFirstResponder此为重写


• - (id)initWithFrame:(CGRect)frame此为重写


• - (void)awakeFromNib此为重写


• - (void)attachTapEvent


• - (void)handleTap:(UITapGestureRecognizer *)recognizer

3. 上代码

• EventableLabel.h，这里面没什么东西

   #import 
   @interface EventableLabel : UILabel
   @end
   



• EventableLabel.m
  
  
  • 使其label可以成为第一响应者
  
  
  • 不过经过实践，好像没有这个也能实现
  
  

   //make the label be able to receive event
   
   
   
    
  (BOOL)canBecomeFirstResponder
   {
   return YES;
   }
   

• 执行某种方法将事件绑定到绑定上


• initWithFrame是在控件初始化的时候绑定


• awakeFromNib是在控件。。。的时候绑定

 //bind the event
 
 
 
  
 
(id)initWithFrame:(CGRect)frame
 {
 self = [super initWithFrame:frame];
 if (self){
 [self attachTapEvent];
 }
 
  NSLog(@"initWithFrame");
  return self;
 
 
 
 
 
}
 
 
 
  
 
(void)awakeFromNib
 {
 [super awakeFromNib];
 [self attachTapEvent];
 
  NSLog(@"awakeFromNib");
 
 
 
 
 
}
 

• 将事件绑定到控件的方法

 //add the tap event
 
 
 
  
 
(void)attachTapEvent
 {
 self.userInteractionEnabled = YES;
 UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(handleTap:)];
 tapGesture.numberOfTapsRequired = 1;
 [self addGestureRecognizer:tapGesture];
 
  NSLog(@"attachTapEvent");
 
 
 
 
 
}
 

• 事件发生时执行的方法


• 对于UITapGestureRecognizer来说，使用UIGestureRecognizerStateEnded来判别动作

 //how to deal with the tap event
 
 
 
  
 
(void)handleTap:(UITapGestureRecognizer *)recognizer
 {
 if(recognizer.state == UIGestureRecognizerStateEnded){
 UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:@"Tap" message:@"Label Tap Event Detected..." delegate:nil cancelButtonTitle:@"Cancel" otherButtonTitles:@"OK", nil];
 
  [alertView show];
  }

  NSLog(@"handleTap");
 
 
 
 
 
}
 

4. 运行代码

• 发现什么也没有


• 因为还没有创建EventableLabel的实例

5. 创建EventableLabel实例

- (void)viewDidLoad {
 [super viewDidLoad];
 // Do any additional setup after loading the view, typically from a nib.
 
 
CGRect rect = CGRectMake(50, 50, 100, 100);
EventableLabel *eventableLabel = [[EventableLabel alloc]initWithFrame:rect];
eventableLabel.text = @"I am here";

[self.view addSubview:eventableLabel];
 
 
}
 

6. 另

• 上述代码中UIAlertView已经在iOS8中所deprecated，取而代之为UIAlertController


• 下面将UIAlertView部分的代码替换为UIalertController
  
  

  • 创建一个UIAlertController

     UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Tap" message:@"Tap Gesture Detected..." preferredStyle:UIAlertControllerStyleAlert];
     

  
  

  • 为alert添加上按钮

     UIAlertAction *alertAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action){
     self.backgroundColor = [UIColor whiteColor];
     }];
     [alert addAction:alertAction];
     

  
  

  • 显示出alert

     UIViewController *viewController = [self getViewController];
     [viewController presentViewController:alert animated:YES completion:nil];
     

  
  
  • 问题来了，显示alert部分的代码为什么如此突兀？
  
  
  
  



• 由于presentViewController:animated:completion:这条消息需要一个UIViewController来发出；然而本类却是一个继承自UILabel的普通控件而已，因此需要寻找一个UIViewController，而刚好，EventableLabel的下一个响应者是ViewController，于是有下列函数，参考自http://hufeng825.github.io/2013/08/29/ios5/

   - (UIViewController *)getViewController
   {
   id object = self;
   while (![object isKindOfClass:[ViewController class]]) {
   object = [object nextResponder];
   }
   return object;
   }
   



• 上面代码不断寻找一个ViewController的类，找到便返回

以上