给uiview添加点击事件

    UIView *leftitleView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 200, 54)];
    [leftitleView addSubview:lab];
    UITapGestureRecognizer *singleTap=[[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(cancel)];
    [leftitleView addGestureRecognizer:singleTap];
    self.navigationItem.leftBarButtonItem=[[UIBarButtonItem alloc]initWithCustomView:leftitleView];