- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

    self.window = [[UIWindowalloc] initWithFrame:[[UIScreenmainScreen] bounds]];

    UILabel *lab1=[[UILabelalloc]initWithFrame:CGRectMake(20, 30, 100, 30)];

    lab1.text=@"helloworld";

　　//设置tag属性

    lab1.tag=1;

    UITapGestureRecognizer *tap=[[UITapGestureRecognizeralloc]initWithTarget:selfaction:@selector(randomColor:)];

    [lab1 addGestureRecognizer:tap];

    lab1.userInteractionEnabled=YES;

    [self.window addSubview:lab1];

    self.window.backgroundColor = [UIColorwhiteColor];

    [self.windowmakeKeyAndVisible];

    returnYES;

}

-(void)randomColor:(UITapGestureRecognizer *)gestureRecognizer

{

　　//通过tag属性来获取label

    UILabel *lab=(UILabel *)[self.window viewWithTag:1];

    lab.backgroundColor=[UIColorcolorWithRed:arc4random()%256/255.0green:arc4random()%256/255.0blue:arc4random()%256/255.0alpha:1];

}