I have a UITabBarController instansiated in my appDelegate, but I need a way to know when the user presses the different tab bar items (buttons on the tab bar).
-UITabBarDelegate protocol to the rescue (with the required didSelectViewController-method)!
With everything wired up in Interface Builder, how do I obtain a reference to the actual UIViewController subclass instance that corresponds to this tab bar item that was pressed?
I need this reference because I need to call a method in one of my UIViewControllers subclasses every time that tab bar item is pressed.
Any suggestions?
- (void)tabBarController:(UITabBarController *)theTabBarController didSelectViewController:(UIViewController *)viewController
{
NSLog(#"%#", [[self.tabBarController selectedViewController] nibName]); // nil, no success here
if ([theTabBarController selectedIndex] == 1) {
MySecondViewController *reference = (MySecondViewController *) viewController;
if ([reference isKindOfClass:[UINavigationController class]]) {
NSLog(#"OMG. It's a UINavigationController class??!"); // kicks in for some reason, shouldn't reference be a MySecondViewController
}
}
Possibly I am not understanding your question correctly, but it seems that what you're asking for is simply the "viewController" parameter which is passed into the method call you've mentioned
- (void)tabBarController:(UITabBarController *)theTabBarController didSelectViewController:(UIViewController *)viewController
UITabBarController also has a property to get the same info
#property(nonatomic, assign) UIViewController *selectedViewController
Related
I have two view controllers (FirstViewController and SecondViewController) and a Tab Bar Controller and I'm using Storyboards. In the FirstViewController user can drag and drop an imageview. So every time a user clicks on the second TabBarItem which displays the SecondViewController I would like to check if the user has dropped the image or not every time she clicks the TabBarItem.
So I understand that this can be done with UITabBarDelegate and with its method -(void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item. But I'm doing something wrong because the method isn't called and I believe this is because I can't set the delegate properly. So I want the SecondViewController to be the delegate for TabBarController.
So in my SecondViewController.h I have the following
#interface SecondViewController : UIViewController<UITabBarDelegate>
And in SecondViewController.m I have
-(void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item {
NSLog(#"%#", item);
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.tabBarController.delegate = self;
}
But nothing happens and when setting the delegate I also get a compiler warning: Assigning to 'id' from incompatible type 'SecondViewController *const __strong'
Please be gentle with me, this is my first app and the first time I'm trying to use delegates.
Add the following code to any of the view controllers
UITabBarController *tabBarController = (UITabBarController*)[UIApplication sharedApplication].keyWindow.rootViewController ;
[tabBarController setDelegate:self];
// add any delegates methods to your class
-(void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController {
NSLog(#"%#", tabBarController);
}
-(void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item;
This method is a delegate method for UITabBar, not UITabBarController, so
self.tabBarController.delegate = self;
will not work.
Tab bar controller has its own UITabBar, but changing the delegate of a tab bar managed by a tab bar controller is not allowed, so just try UITabBarControllerDelegate method like this:
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController
NSLog(#"%#", item);
}
For more detail check info
Thanks
I imported and implemented the following. Hope it helps.
- (void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item
{
if (_mainTab.selectedItem.tag == 1) {
NSLog(#"TAB 1");
}
else if (_mainTab.selectedItem.tag == 2) {
NSLog(#"TAB2");
}
else if (_mainTab.selectedItem.tag == 3)
{
NSLog(#"TAB3");
}
else
{
NSLog(#"TAB NOT WORKING");
}
}
You are using the wrong delegate protocol UITabBarDelegate is usually used for customizing the UITabBar objects. You need to use UITabBarControllerDelegate protocol in order to check if a tab is selected or customize the behavior of tabs.
You should implement UITabBarControllerDelegate protocol instead and use this delegates callback to track selection:
tabBarController:didSelectViewController:
Next thing is, that you should initialize delegate before it will be called. ViewDidLoad will be called after tabbarcontroller will try to talk to delegate.
In order to get rid of the compiler warning your SecondViewController should conform to the UITabBarControllerDelegate protocol instead of the UITabBarDelegate protocol.
#interface SecondViewController : UIViewController<UITabBarControllerDelegate>
I have a tab bar with 3 items. Each points to a UINavigationController. Each UINavigationController has several viewControllers beneath. I'm wanting to reset back to the first controller in the navigation when any tab bar item is pressed.
I've specified my TabBarController implementation as a delegate
self.delegate = self and my method below (running in my TabBarController implementation works returning UINavigationControllers.
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController
{
NSLog(#"%#", viewController);
}
With the log file showing e.g.
UINavigationController: 0x8a31a90>2012-12-31 02:16:40.035 Demo[6142:c07]
when I try popToRootViewController or popViewController within this method it doesn't seem to work. I don't get any errors but my viewControllers don't reset. It seems like I've made a really basic error here but I can't tell what.
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController
{
NSLog(#"%#", viewController);
[self.navigationController popToRootViewControllerAnimated:YES];
[[self navigationController] popViewControllerAnimated:YES];
}
You need to popToRootViewController on the navigationController (viewcontroller) - not the TabViewController (self).
[viewController popToRootViewControllerAnimated:YES];
I'm not sure if this will help. I had a lot of trouble getting this to work and found that I needed to do the following:
In root view controller (first view app comes to), add a delegate in the .h file.
#interface MGMProductsViewController : UIViewController <UITabBarControllerDelegate>
Add the below code to viewDidLoad in root view controller (.m file).
[self.tabBarController setDelegate:self];
Override method in root view controller (.m file) with the below.
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController
{
if ([viewController isKindOfClass:[UINavigationController class]])
{
[(UINavigationController*)viewController popToRootViewControllerAnimated:NO];
}
}
I can't attribute this to anyone as I couldn't find the appropriate code again. I think I pieced it together from a few places though the '[self.tabBarController setDelegate:self]' looked to be the key to it working for me.
Good luck.
How can i get the index of the tabBar when i touch a tab?
I´ve extended my class to < UITabBarController > and added the method
- (void)tabBarController:(UITabBarController *)tabBarController
didSelectViewController:(UIViewController *)viewController
{
if (viewController == tabBarController.moreNavigationController)
{
tabBarController.moreNavigationController.delegate = self;
}
}
But that method isn´t triggered when i touch a tab item.
What should i do?
UITabBarController has a property selectedIndex that you can use to find the selected tab.
More information about the UITabBarController can be found here
Also be sure to set the delegate property of your UITabBarController, otherwise the delegate messages (such as didSelectViewController:) will not be received.
Did you set the delegate of the UITabBarController to your delegate class when you create it?
Can any one help me,
when i am using my UITabBarController delegate it is not working..
I called a delegate method like this..
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController
{
[self.navigationController popToRootViewControllerAnimated:NO];
}
If what you're doing is subclassing a UITabBarController, then... oddly enough... you can get it working by setting itself as a delegate:
- (void)viewDidLoad
{
[super viewDidLoad];
self.delegate = self;
}
Then the didSelectViewController action will fire normally:
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController {
NSLog(#"View Changed");
}
Don't forget to add your UITabBarControllerDelegate class to your .h file:
#interface MyTabBarController : UITabBarController <UITabBarControllerDelegate>
#end
If you are using tab bar customizing by extending UITabBarController and trying to change tab bar selected index programmatically then it will not call delegates.
Please see the note inside "UITabBarDelegate":
// Note: called when a new view is selected by the user (but not programmatically)
This might help you
-(void)applicationDidFinishLaunching:(UIApplication *)application {
tabBarController.delegate=self;
// Add the tab bar controller's current view as a subview of the window
[window addSubview:tabBarController.view];
}
specify
UITabbarcontrollerDelegate in .h file
then
-(void)applicationDidFinishLaunching:(UIApplication *)application {
tabBarController.delegate=self;
// Add the tab bar controller's current view as a subview of the window
[window addSubview:tabBarController.view];
}
Read the documents to get a deeper understanding of the relationships between navigation controllers, tabBar controllers, and the view and navigation hierarchy.
Then review the code you've provided. Which view/controller is the container? You are popping the navigationController of self, which is not the same as the tabBarController. I don't think you actually need this method if you are looking to switch between tabs.
Try commenting out this method. It is an optional method in the UITabBarController delegate protocol. If you comment it out, you should get the default behavior of the tab controller, which should be to select the appropriate viewController and switch to the new view.
You typically only need to use this method if you want some action taken as you switch between view controllers.
Trying to mimic/copy the built-in address book, specifically the behavior when editing a contact or viewing an existing contact's Info from inside the Phone app. When you navigate to another tab, the editing state is reset and the "New Contact" or "Info" view is popped so that when you come back to the Contacts tab, you are back at the root table view.
I have most of this working inside viewWillDisappear using setEditing: and popToViewController: however I get strange behavior when the user navigates from the Info view to the table view using the back button. Even if I pop to the root table view controller, it seems to be using the default UITableViewController class and not my subclass (e.g. standard selection behaviors instead of my overrides to push the detail view.)
Any hints? IPD
Here's some code to illustrate:
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
// This is to clean up from the colored bar in detail view
self.navigationController.navigationBar.tintColor = nil;
// These are to match the behaviour of Contacts app
[self setEditing:NO animated:NO];
// This is the tricky part: works when switching tabs, but not when back button was going to pop anyway!!
[self.navigationController popToViewController:rootViewControllerForTab animated:NO];
}
The -viewWillDisappear: method is not the best place for modifying the view controller stack for your navigationController because it is triggered both when you switch tabs and when a view is pushed on top of it.
I played around with this a bit and found that the best place for this is in the -[UITabBarControllerDelegate tabBarController:didSelectViewController:] method. So, first you need to designate an object to be the delegate for your tab bar (I used the app delegate). Bind the delegate property of your UITabBarController to an object implementing the UITabBarControllerDelegate protocol in code or in Interface Builder.
Then, implement the -tabBarController:didSelectViewController: method. The trick now is how to tell when your "address book" tab is being switched to. I kept track of the view controller for the tab in question using a property of type UINavigationController (the root view controller for the tab). After binding the tab1NavController property to the actual instance using Interface Builder, it can be used to compare to the viewController parameter to see what tab was just selected.
#interface Pop2RootTabSwitchAppDelegate : NSObject
<UIApplicationDelegate, UITabBarControllerDelegate> {
UINavigationController *tab1NavController;
}
#property (nonatomic, retain) IBOutlet UINavigationController *tab1NavController;
#end
#implementation Pop2RootTabSwitchAppDelegate
- (void)tabBarController:(UITabBarController *)tabBarController
didSelectViewController:(UIViewController *)viewController {
NSLog(#"[%# tabBarController:%# didSelectViewController:%#]", [self class],
tabBarController, viewController);
if (viewController == tab1NavController) {
NSLog(#"viewController == tab1NavController");
[tab1NavController popToRootViewControllerAnimated:NO];
}
}