Pop to root view when tab is selected

问题:

I've been having some trouble with something I thought might be easy. I have a table in my root view controller, when a row is selected I push a new view and from there I go to another tab.

My question is how do I make sure that as soon as the user taps the first tab the navigation controller will pop to root?

回答1:

Following delegate is called while each tab is selected on tabbar.

-(void) tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController

Put following code inside this delegate method.

if ([viewController isKindOfClass:[UINavigationController class]]) 
    {
        [(UINavigationController *)viewController popToRootViewControllerAnimated:NO];
    }

its working fine on my app.

回答2:

For Swift lovers:

import UIKit

class YourTabBarControllerHere: UITabBarController,
UITabBarControllerDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()
        self.delegate = self;
    }

    func tabBarController(tabBarController: UITabBarController,
        didSelectViewController viewController: UIViewController) {
            if let vc = viewController as? UINavigationController {
                vc.popViewControllerAnimated(animated: false);
            }
    }
}

Edit: Swift 3 update, thanks to @Justin Oroz for pointing that out.

回答3:

In Swift 3.1

Add UITabBarControllerDelegate to your TabBar Class:

class YourClass: UITabBarController, UITabBarControllerDelegate {

After:

override func tabBar(tabBar: UITabBar, didSelectItem item: UITabBarItem) {

let yourView = self.viewControllers![self.selectedIndex] as! UINavigationController
yourView .popToRootViewControllerAnimated(false) 

}

回答4:

What you are trying to do sounds a little bit odd. Have you read the Human Interface Guidelines on combining UINavigationControllers and UITabBarControllers?

However, what you need to do is detect the selection of the tab by setting a delegate for your UITabBarController and implementing the tabBarController:didSelectViewController: delegate method. In this method you need to pop back to the root view controller using UINavigationController's popToRootViewControllerAnimated: method.

回答5:

[self.navigationController popToRootViewControllerAnimated:NO];

回答6:

First, you should create subclass of UITabbarController and add Observer:

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.tabBar addObserver:self forKeyPath:@"selectedItem" options:NSKeyValueObservingOptionOld | NSKeyValueObservingOptionNew context:nil];
}

When tabbar is selected, We will process in method:

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
    if ([keyPath isEqualToString:@"selectedItem"] && [object isKindOfClass:[UITabBar class]]){
        UITabBar *bar = (UITabBar *)object; // The object will be the bar we're observing.
        // The change dictionary will contain the previous tabBarItem for the "old" key.
        UITabBarItem *wasItem = [change objectForKey:NSKeyValueChangeOldKey];
        NSUInteger was = [bar.items indexOfObject:wasItem];
        // The same is true for the new tabBarItem but it will be under the "new" key.
        UITabBarItem *isItem = [change objectForKey:NSKeyValueChangeNewKey];
        NSUInteger is = [bar.items indexOfObject:isItem];
        if (is == was) {
           UIViewController *vc = self.viewControllers[is];
            if ([vc isKindOfClass:[UINavigationController class]]) {
                [(UINavigationController *)vc popToRootViewControllerAnimated:YES];
            }
        }
    }
}

回答7:

The UTabController suggests a different UX for letting a user "pop to root". When switching back to a tab, it keeps the full UINav stack from before. If they tap the bar item a second time (tapping the selected tab), only then does it pop to root. That's all automatic. Some apps, like instagram, allow a third tap to scroll to top.

I'd suggest sticking with the defaults as that's what users will be expecting.

回答8:

The below had worked for me .This code in swift 3:

1> subclass UITabbarController and implement two below method with one iVAr:
class MyTabBarController: UITabBarController ,UITabBarControllerDelegate { var previousSelectedTabIndex : Int = -1 }

2> set the tabbar delegate in viewdidLoad

override func viewDidLoad() {    
    super.viewDidLoad()
    self.delegate = self    // you must do it}  

func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {

    self.previousSelectedTabIndex = tabBarController.selectedIndex
}     
func tabBarController(_ tabBarController: UITabBarController,
                               shouldSelect viewController: UIViewController) -> Bool {    

    if  self.previousSelectedTabIndex == tabBarController.selectedIndex {
        let   nav  =  viewController as! UINavigationController // mine in nav_VC
        for vc in nav.childViewControllers {
            if vc is YUOR_DESIRED_VIEW_CONTROLLER {
            nav.popToViewController(vc, animated: true)
            return false// IT WONT LET YOU GO TO delegate METHOD
            }
        }
    }
 return true
}    

tabBarController.selectedIndex give you the selected tab

In tabBarController_shouldSelect_viewController method you can set your desired view controller with some easy calculation.
if you are not getting the above code play with both above method and you come to know how both working together

回答9:

Swift 4.2

The solution that works for me is to subclass the UITabBarController and add the two delegate functions as follows:

import UIKit

class MyCustomTabBarController: UITabBarController, UITabBarControllerDelegate {
    var previousSelectedTabIndex:Int = 0

override func viewDidLoad() {
    super.viewDidLoad()
    self.delegate = self
}

func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {
    self.previousSelectedTabIndex = tabBarController.selectedIndex
}


override func tabBar(_ tabBar: UITabBar, didSelect item:
    UITabBarItem) {
    let vc = self.viewControllers![previousSelectedTabIndex] as! UINavigationController
    vc.popToRootViewController(animated: false)

}

}

Make sure you set animated to false otherwise you will get

 Unbalanced calls to begin/end appearance transitions for the targeted ViewController