Three20基于URL的导航+标签栏示例?

我刚发现做起来有多容易 state persistence with Three20 library . 但是,我无法理解如何将URL映射器与选项卡一起使用。( UITabBarController )

情况是这样的:

1. 我有四个选项卡和不同的控制器: FirstViewController , SecondViewController ,请 ThirdViewController 和 FourthViewController .
2. 我想把它们映射到 tt://tabs/first … tt://tabs/fourth 分别在应用程序关闭时将其保存到某个位置,以便在应用程序再次启动时自动打开以前查看的选项卡。

我的代码到目前为止:

// Init the tab bar
tabBarController = [[UITabBarController alloc] init];
[tabBarController setDelegate:self];

// Init the navigator
TTNavigator *navigator = [TTNavigator navigator];
[navigator setWindow:window];
[navigator setPersistenceMode:TTNavigatorPersistenceModeAll];

// Begin mapping
TTURLMap *map = [navigator URLMap];
[map from:@"tt://tabs" toViewController:[UIViewController class]];
[map from:@"tt://tabs/first" toViewController:[FirstViewController class]];
[map from:@"tt://tabs/second" toViewController:[SecondViewController class]];
[map from:@"tt://tabs/third" toViewController:[ThirdViewController class]];
[map from:@"tt://tabs/fourth" toViewController:[FourthViewController class]];

// Try restoring
if (! [navigator restoreViewControllers]) {
  // Open default
  TTURLAction *defaultAction = [[TTURLAction alloc] initWithURLPath:@"tt://tabs/default"];
  [defaultAction setParentURLPath:@"tt://tabs"];
  [navigator openURLAction:defaultAction];
}

// Put view controllers to tab bar
[tabBarController setViewControllers:[NSArray arrayWithObjects:
                                      [[FirstViewController alloc] init],
                                      [[SecondViewController alloc] init],
                                      [[ThirdViewController alloc] init],
                                      [[FourthViewController alloc] init],
                                      nil]];

[window addSubview:tabBarController.view];
[window makeKeyAndVisible];

我如何得到 TTNavigator 打开上次打开的选项卡,如果没有-回退到 FirstView控制器 ?