没用storyboard

没有用到storyboard的话，需要在系统初始化完成之前进行恢复
需要在这个方法里面

- (BOOL)application:(UIApplication *)application willFinishLaunchingWithOptions:(nullable NSDictionary<UIApplicationLaunchOptionsKey, id> *)launchOptions {
    CGRect frame = [UIScreen mainScreen].bounds;
    self.window = [[UIWindow alloc] initWithFrame:frame];
    self.window.backgroundColor = [UIColor whiteColor];
    //设置恢复的唯一标识 如果没有对window进行保存的相关操作，则可以不设置
    self.window.restorationIdentifier = NSStringFromClass([UIWindow class]);
    PGTabBarViewController *tabBar = [PGTabBarViewController sharedGTTabBar];
    //设置恢复的唯一标识
    tabBar.restorationIdentifier = NSStringFromClass([PGTabBarViewController class]);
    self.window.rootViewController = tabBar;
    return true;
}

PGTabBarViewController关键代码

- (void)viewDidLoad {
    [super viewDidLoad];
    
    
    FirstController *firstController = [[FirstController alloc] init];
    [self setupChildViewController:firstController title:@"第一"];
    SecondTableController *second = [[SecondTableController alloc] initWithNibName:@"SecondTableController" bundle:nil];
    [self setupChildViewController:second title:@"第二"];
    ThirdViewController *third = [[ThirdViewController alloc] initWithNibName:@"ThirdViewController" bundle:nil];
    [self setupChildViewController:third title:@"第三"];
    FourTableController *four = [[FourTableController alloc] init];
    [self setupChildViewController:four title:@"第四"];
}

- (void)setupChildViewController:(UIViewController *)controller title:(NSString *)title {
    UITabBarItem *tabBarItem = controller.tabBarItem;
    tabBarItem.title = title;
    [tabBarItem setTitleTextAttributes:@{NSForegroundColorAttributeName: [UIColor grayColor]} forState:UIControlStateNormal];
    [tabBarItem setTitleTextAttributes:@{NSForegroundColorAttributeName: [UIColor blueColor]} forState:UIControlStateSelected];
    tabBarItem.image = [self imageWithColor:[UIColor greenColor]];
    PGNavigationController *navigationController = [[PGNavigationController alloc] initWithRootViewController:controller];
    //设置需要恢复的唯一标识
    navigationController.restorationIdentifier = NSStringFromClass([controller class]);
    [self addChildViewController:navigationController];
}

FirstController跟FourTableController没有用到xib，恢复标识在viewDidLoad设置即可。

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.restorationIdentifier = NSStringFromClass([self class]);
}

SecondTableController跟ThirdViewController用到了xib，则需要在initWithNibName方法进行设置

- (instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    if ([super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {
        self.restorationIdentifier = NSStringFromClass([self class]);
    }
    return self;
}

子页面指的是没有在willFinishLaunchingWithOptions跟PGTabBarViewController里面初始化的页面，也就是不是PGTabBarViewController直接嵌套的页面
如果还有子页面，则需要设置

@interface PersonDetailController ()<UIViewControllerRestoration>

@end

@implementation PersonDetailController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.restorationIdentifier = NSStringFromClass(self.class);
    self.restorationClass = self.class;
}

#pragma mark - UIViewControllerRestoration
+ (nullable UIViewController *) viewControllerWithRestorationIdentifierPath:(NSArray<NSString *> *)identifierComponents coder:(NSCoder *)coder {
    PersonDetailController *ctrl = [[PersonDetailController alloc]init];
    return ctrl;
}

@end

保存与恢复数据

- (void)encodeRestorableStateWithCoder:(NSCoder *)coder {
    
    [super encodeRestorableStateWithCoder:coder];
    
}

- (void)decodeRestorableStateWithCoder:(NSCoder *)coder {
    
    [super decodeRestorableStateWithCoder:coder];
    
}