当我在tabBarController中的选项卡之间切换时，将调用哪个方法？

Question

which method will be called when i switch between tabs in tabBarController

i know at first time it will call viewDidLoad method ,i want to know is there any method that come in action when i switch to a particular tab (second time or third time ) .

regards

Answer 1

You can use the UITabBarControllerDelegate method tabBarController:didSelectViewController: :

- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController {
    //do something
}

Answer 2

This is pretty old, but it does come up on Google and is linked to from another answer. So, I thought I'd update it.

If your UITableBarController is displaying a UIViewController (ie its view) then you have to check the ViewController methods that fire when a view disappears and appears. You could use viewWillDisappear to find out if your view is about to be switched away from, and viewWillAppear to test if your view just got switched back to. Notice, the TabBarController typically keeps the ViewControllers loaded, just their views are moved out and in. The problem with using the TabBarDelegate method is that you need to know the name of your viewController, which makes that a dependency. Change the name and it will probably break with xcode's poor ability to rename Class String representations. Avoid it. Besides you don't want a bunch of conditional junk checking to see if your tabbar just loaded a particular tab unless you cannot avoid it. The other thing to notice is that if a particular tab presents a TableViewController you may have to resort to other techniques if you need data in the cells to change in response to being switched away from. I'm using willMoveToWindow:(UIWindow *)newWindow to get notified in the UITableViewCell case when the view goes away. There's probably a better way.

Answer 3

The method viewWillDisappear: is triggered each time you are about to leave the current view controller (and hence the current tab) and viewWillAppear: is triggered each time a view is about to be displayed.

A full reference for these methods can be found in the UIViewController docs.