需要同时将视图控制器和对应的view
加载到当前视图控制器上
SecondController *second = [[SecondController alloc]init];
second.view.frame = CGRectMake(20, 20, self.view.bounds.size.width-40, self.view.bounds.size.height-40);
[self addChildViewController:second];
[self.view addSubview:second.view];
加载到当前视图控制器上
SecondController *second = [[SecondController alloc]init];
second.view.frame = CGRectMake(20, 20, self.view.bounds.size.width-40, self.view.bounds.size.height-40);
[self addChildViewController:second];
[self.view addSubview:second.view];