一.在Xcode11.0之前新建的项目，设置根视图，代码如下：
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
TabViewController *ltabVC = [[TabViewController alloc]init];
ltabVC.delegate = self;
self.window.rootViewController = ltabVC;
[self.window makeKeyAndVisible];
return YES;
}
二.在Xcode11.0之后新建的项目，项目会自动生成AppDelegate文件之外，还会生成SceneDelegate文件。
设置根视图代码如下：
（兼容iOS13和iOS13以前的项目AppDelegate和SceneDelegate类方法里设置）
1.在AppDelegate.h里加声明window：
@property (nonatomic, strong) UIWindow * window;
2.在AppDelegate.m设置：
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
if (@available(iOS 13.0, *)) {
} else {
self.window = [[UIWindow alloc]initWithFrame:[UIScreen mainScreen].bounds];
self.window.rootViewController = [[UITabBarController alloc]init];
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
}
return YES;
}
3.在SceneDelegate.m里设置
- (void)scene:(UIScene *)scene willConnectToSession:(UISceneSession *)session options:(UISceneConnectionOptions *)connectionOptions {
// Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
// If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
// This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
UIWindowScene *windowScene = (UIWindowScene *)scene;
self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
self.window = [[UIWindow alloc] initWithWindowScene:windowScene];
[self.window setWindowScene:windowScene];
[self.window setBackgroundColor:[UIColor whiteColor]];
[self.window setRootViewController:[UITabBarController new]];
[self.window makeKeyAndVisible];
}
获取window
if (@available(iOS 13.0, *)) {
window = [UIApplication sharedApplication].windows[0];
} else {
window = [UIApplication sharedApplication].delegate.window;
}
