I have tabbed iOS application. I need to know which tab is active and detect when tab is changed. In storyboard I have a tab view controller, which changes the view when you click a tab fine. I created a class TabBarController and it is defined as follows:
Header
#interface TabBarController : UITabBarController <UITabBarControllerDelegate>
#end
Implementation
#import "TabBarController.h"
#implementation TabBarController
// In the initialization section, set the delegate
- (id) init
{
self = [super init];
if (self)
{
self.delegate = self;
}
return self;
}
- (void)tabBarController:(UITabBarController *)tabBarController
didSelectViewController:(UIViewController *)viewController
{
NSLog(#"controller class: %#", NSStringFromClass([viewController class]));
NSLog(#"controller title: %#", viewController.title);
}
#end
However, I couldn't detect tab changes with the code above. What do you think that the problem is?
I haven't linked my tab view to any outlets, but segues to other views. Is this the problem? Then, where should I link my outlet to?
Have you confirmed that your init method is being called? I don't think init is the designated initializer for UITabBarController and may not be called when loading the controller from a nib/storyboard.
If that's the case you may find it easier to set the delegate in your viewDidLoad since that will be called regardless of how the object is initialized or else make sure you set the delegate when -initWithNibName:bundle: or -initWithCoder is used to instantiate the object.
Solution to this is the implementation viewDidLoad as follows:
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
NSLog(#"Tabs showed up!");
self.delegate = self;
}
Related
Trying to achieve
When I tap on the tabbaritem say #2, it will called the method and reload the web view.
Issue
When I tap on the tabbaritem, the method is called but web view did not reload.
Did not load the web view
Question
If I called the method on the VC itself. I can manage to reload the web view. Only if I called it when the tabbaritem is tapped, it doesn't reload the web view.
Code
MyTabBarController.m
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController {
NSLog(#"controller class: %#", NSStringFromClass([viewController class]));
NSLog(#"controller title: %#", viewController.title);
if (viewController == [tabBarController.viewControllers objectAtIndex:2])
{
[(UINavigationController *)viewController popToRootViewControllerAnimated:YES];
tabBarController.delegate = self;
[[[Classes alloc] init] LoadClasses];
}else if (viewController == [tabBarController.viewControllers objectAtIndex:3]){
[(UINavigationController *)viewController popToRootViewControllerAnimated:YES];
tabBarController.moreNavigationController.delegate = self;
[[[Gym alloc] init] handleRefreshGym:nil];
}else{
[(UINavigationController *)viewController popToRootViewControllerAnimated:NO];
}
}
Classes.m
- (void)LoadClasses {
sURL = #"www.share-fitness.com/apps/class.asp?memCode=SF100012&dtpClass=13/09/2018&lang=EN&lat=37.785835&long=-122.406418&ver=1&plat=IOS"
NSLog(#"The URL To be loaded %#", sURL);
NSURL *url = [NSURL URLWithString:sURL];
sRefresh = sURL;
[[NSURLCache sharedURLCache] removeAllCachedResponses];
NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url];
[webView loadRequest:urlRequest];
[webView setDelegate:(id<UIWebViewDelegate>)self];
UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
[refreshControl addTarget:self action:#selector(handleRefresh:) forControlEvents:UIControlEventValueChanged];
[webView.scrollView addSubview:refreshControl];
}
As I mentioned in my other reply Objective-C: How to properly set didSelectViewController method for TabBarController, so I can refresh the VC everytime it is tapped, I don't think it's good User Experience to be refreshing the view from the server every time the tab bar is selected (this will get very annoying for users to wait every time for the server to refresh the data)
That being said, the issue with the code you posted is that you're initializing a new instance of your classes in the TabBarControllerDelegate method so the method will be called on this new instance instead of on the one that's displaying/exists in your TabBarController's view controllers. Specifically these two lines are initializing the new instances:
[[[Classes alloc] init] LoadClasses];
[[[Gym alloc] init] handleRefreshGym:nil];
Instead you should be finding the instance that already exists, and calling the method on them.
I would recommend creating a ParentViewController with a public method along the lines of - (void)doStuffWhenTabBarControllerSelects; (just example naming to be clear what's it doing to you) then have each of the view controllers you'd like to have do something when they're selected be child classes of this parent (and have their own implementation of - (void)doStuffWhenTabBarControllerSelects;). This way in the TabBarController's delegate method, you can just find the appropriate instance of ParentViewController (associated with the view controller being selected) and call the - (void)doStuffWhenTabBarControllerSelects; method on it.
Here's an example of what I mean:
ParentViewController.h:
#import <UIKit/UIKit.h>
NS_ASSUME_NONNULL_BEGIN
#interface ParentViewController : UIViewController
- (void)doStuffWhenTabBarControllerSelects;
#end
NS_ASSUME_NONNULL_END
ParentViewController.m:
#import "ParentViewController.h"
#interface ParentViewController ()
#end
#implementation ParentViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
}
- (void)doStuffWhenTabBarControllerSelects {
NSLog(#"Fallback implementation if this method isn't implemented by the child class");
}
#end
FirstViewController.h:
#import <UIKit/UIKit.h>
#import "ParentViewController.h"
#interface FirstViewController : ParentViewController
#end
FirstViewController.m:
#import "FirstViewController.h"
#interface FirstViewController ()
#end
#implementation FirstViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)doStuffWhenTabBarControllerSelects {
NSLog(#"I'm doing stuff on the %# when the tab bar controller delegate calls back to selection", NSStringFromClass([self class]));
}
#end
SecondViewController.h:
#import <UIKit/UIKit.h>
#import "ParentViewController.h"
#interface SecondViewController : ParentViewController
#end
SecondViewController.m:
#import "SecondViewController.h"
#interface SecondViewController ()
#end
#implementation SecondViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)doStuffWhenTabBarControllerSelects {
NSLog(#"I'm doing stuff on the %# when the tab bar controller delegate calls back to selection", NSStringFromClass([self class]));
}
#end
MyTabBarController.h:
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
NS_ASSUME_NONNULL_BEGIN
#interface MyTabBarController : UITabBarController <UITabBarControllerDelegate>
#end
NS_ASSUME_NONNULL_END
MyTabBarController.m:
#import "MyTabBarController.h"
#import "ParentViewController.h"
#implementation MyTabBarController
- (void)viewDidLoad {
[super viewDidLoad];
self.delegate = self;
}
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController {
// since your view controllers are embedded in nav controllers, let's make sure we're getting a nav controller
if ([viewController isKindOfClass:[UINavigationController class]]) {
// we're expecting a nav controller so cast it to a nav here
UINavigationController *navController = (UINavigationController *)viewController;
// now grab the first view controller from that nav controller
UIViewController *firstViewControllerInNav = navController.viewControllers.firstObject;
// check to make sure it's what we're expecting (ParentViewController)
if ([firstViewControllerInNav isKindOfClass:[ParentViewController class]]) {
// cast it to our parent view controller class
ParentViewController *viewControllerToCallMethodOnAfterSelection = (ParentViewController *)firstViewControllerInNav;
[viewControllerToCallMethodOnAfterSelection doStuffWhenTabBarControllerSelects];
}
}
}
#end
Then when you select between the two tabs you'll this is the output:
I'm doing stuff on the FirstViewController when the tab bar controller delegate calls back to selection
I'm doing stuff on the SecondViewController when the tab bar controller delegate calls back to selection
I'd recommend doing some additional research/reading of the documentation:
There's a good amount of beginner information here: https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/DefiningClasses/DefiningClasses.html#//apple_ref/doc/uid/TP40011210-CH3-SW1
UITabBarController: https://developer.apple.com/documentation/uikit/uitabbarcontroller?language=objc
UITabBarControllerDelegate:
https://developer.apple.com/documentation/uikit/uitabbarcontrollerdelegate?language=objc
One other helpful hint is that within Xcode you can hold down on the option key and click on something to show a quicklook into the explanation/documentation
You can also right click on something and "Jump To Definition". The majority of Apple's implementations will will have additional information in the header.
Here's the example of what's in the header of UITabBarController:
/*!
UITabBarController manages a button bar and transition view, for an application with multiple top-level modes.
To use in your application, add its view to the view hierarchy, then add top-level view controllers in order.
Most clients will not need to subclass UITabBarController.
If more than five view controllers are added to a tab bar controller, only the first four will display.
The rest will be accessible under an automatically generated More item.
UITabBarController is rotatable if all of its view controllers are rotatable.
*/
NS_CLASS_AVAILABLE_IOS(2_0) #interface UITabBarController : UIViewController <UITabBarDelegate, NSCoding>
As well as under the Help Menu there's "Developer Documentation" (CMD + SHIFT + 0) which has a multitude of useful information.
I'm using a UICollectionView with Storyboard and trying to subclass the UICollectionViewFlowLayout but it doesn't seem to work.
I've created the subclass CollectionViewFlowLayout :
#import "CollectionViewFlowLayout.h"
#implementation CollectionViewFlowLayout
-(id)init
{
NSLog(#"Init of CollectionViewFlowLayout");
if (!(self = [super init])) return nil;
self.itemSize = CGSizeMake(250, 250);
return self;
}
#end
And in the Storyboard's Identity Inspector I changed the class for the flow layout:
But when I save/build/run, the itemSize is not set at 250 and my NSLog isn't being output.
I've seen in examples such as this that you can set the layout in the collectionView controller, but I sort of assumed that wasn't necessary if you set it in the storyboard.
Objects loaded from the storyboard use initWithCoder:, not init. Move your setup code there instead, or have a common method that is called from each initialiser.
I subclassed UIViewController as STViewController and noticed that classes inheriting from STViewController have their viewDidLoad method being called repeatedly. Ultimately crashing the app. STViewController is basically a blank implementation at this point. I am subclassing as shown below:
#import "STViewController.h"
#interface WelcomeViewController : STViewController {
STViewController.h
#import <UIKit/UIKit.h>
#interface STViewController : UIViewController
{
}
#end
STViewController.m
#import "STViewController.h"
#implementation STViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)loadView
{
// Implement loadView to create a view hierarchy programmatically, without using a nib.
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
#end
viewDidLoad() from WelcomeViewController.m
- (void)viewDidLoad
{
[super viewDidLoad];
// hide the buttons
[[self signUp] setHidden: YES];
[[self logIn] setHidden: YES];
}
You are overriding loadView, but your implementation is empty, and you're not assigning a view. Remove the loadView override.
From UIViewController Class Reference (emphasis mine):
You should never call this method directly. The view controller calls
this method when the view property is requested but is currently nil.
If you create your views manually, you must override this method and
use it to create your views. If you use Interface Builder to create
your views and initialize the view controller—that is, you initialize
the view using the initWithNibName:bundle: method, set the nibName and
nibBundle properties directly, or create both your views and view
controller in Interface Builder—then you must not override this
method.
The default implementation of this method looks for valid nib
information and uses that information to load the associated nib file.
If no nib information is specified, the default implementation creates
a plain UIView object and makes it the main view.
If you override this method in order to create your views manually,
you should do so and assign the root view of your hierarchy to the
view property. (The views you create should be unique instances and
should not be shared with any other view controller object.) Your
custom implementation of this method should not call super.
I am new to storyboards and I have set up a segue from a button to a view controller. This view controller is of a custom subclass SFListViewController, which has a designated initializer initWithList:.
Using the designated initializer is the only way to correctly initialize the view controller. However, when using segues the designated initializer won't be called (obviously).
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([segue.identifier isEqualToString:#"Show List"]) {
SFListViewController *listViewController = segue.destinationViewController;
// ????
}
}
How can I make the segue call the designated initializer when performed?
As far as I know this is not possible since the storyboard framework simply calls alloc and init on the class you define in Interfacebuilder. Additionally the segue's destinationViewController attribute is read-only so you couldn't simply replace the existing ViewController either.
The only way to use Storyboarding would probably be to create a wrapper-class that internally instantiates the SFListViewController with the desired attributes and then functions as a proxy object and thus propagates viewDid*** and viewWill***-methods to the wrapped class and also returning the wrapped VC's view in a readonly view property... You get the idea.
Generally there are a number of alternative ways to initialize a UIViewController in such a case:
There is an option to specify "User defined runtime Attributes" which could be used for initialisation.
Override the prepareForSegue: method, like you tried, in your root ViewController and do "post-alloc-init-initialisation" there.
If worst comes worst, you could fall back to an IBAction in order to be able to initialize the ViewController yourself.
I hope this helps.
Edit: I can verify that the Proxy-Approach works since I just came across a similar problem with ABPeoplePickerNavigationController where this approach worked nicely. Since we've set up the thing in our story board please note that you have to use awakeFromNib in order to do initial configuration (instead of some init method).
This is the code for my wrapper class:
#import "PeoplePickerViewControllerWrapper.h"
#implementation PeoplePickerViewControllerWrapper
#synthesize ppvc = _ppvc; // This is the object I'm proxying (The proxyee so to speak)
#synthesize delegate = _delegate;
- (void)awakeFromNib
{
self.ppvc = [[ABPeoplePickerNavigationController alloc] init ];
self.ppvc.peoplePickerDelegate = self;
self.ppvc.addressBook = ABAddressBookCreate();
self.ppvc.displayedProperties = [NSArray arrayWithObject:[NSNumber numberWithInt:kABPersonPhoneProperty]];
}
#pragma mark - View lifecycle
- (void)loadView
{
[super loadView];
[self.ppvc loadView];
}
- (void)viewDidLoad
{
[super viewDidLoad];
[self.ppvc viewDidLoad];
}
-(void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
[self.ppvc viewWillAppear:animated];
}
-(void)viewDidDisappear:(BOOL)animated{
[super viewDidDisappear:animated];
[self.ppvc viewDidDisappear:animated];
}
-(UIView *)view{
return self.ppvc.view;
}
- (void)viewDidUnload
{
[super viewDidUnload];
[self.ppvc viewDidUnload];
}
I've got a TabBarController in my app and in it I've got a few NavigationControllers. I've got all this stuff simply made in interface builder.
Now I want to implement my custom navigationcontroller so I created a class:
#import <UIKit/UIKit.h>
#interface DetailNavigationController : UINavigationController
#end
#implementation DetailNavigationController
- (id)initWithRootViewController:(UIViewController *)rootViewController
{
self = [super initWithRootViewController:rootViewController];
if (self) {
NSLog(#"I work!");
}
return self;
}
- (void) dealloc {
[super dealloc];
}
#end
And in Interface builder I added this class as Custom Class to the navigation controller I want. Now when I start the app and select the tab with this navigation controller it works but the initWithRootController is not called. I guess it's completely ignoring the class and runs as default navigation controller.
Do I need to specify anything more in interface builder or do I need to specify this controller programatically somewhere in tabbar delegate?
Thanks.
If you're creating the navigation controller in interface builder, you will need to override initWithCoder:, not initWithRootViewController:. The xib contains an instantiated version of your object, with the root view controller already set.