视图界面切换

首先在在AppDelegate.m里的：（BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions方法中加入ViewController *viewcontroller=[ViewController new];
    UINavigationController *uinavigationcontroller=[[UINavigationController alloc]initWithRootViewController:viewcontroller];//先将ViewController添加到navigation上；
    self.window.rootViewController=uinavigationcontroller;//navigation加在window上

接下来页面之间的跳转通过（比如a➡️b）：在a类事件函数中添加：[self.navigationController pushViewController:b animated:true];可以实现a跳到b。

如果想回到上一级一面可以写：self.navigationController popViewControllerAnimated:YES];
}
如果想跳回首界面：self.navigationController popRootViewControllerAnimated:YES];
}