Is there any way to automatically call a custom method when switching views usig a UITabBarController? Like, I want to he able to, when I set a NSString in one view in a UILabel, haave it automatically update a different label on a different tab with the same string. Thank you!
Yes, take a look at the UITabBarControllerDelegate protocol. All you have to do is register your object as the tab bar delegate and implement the shouldSelect or didSelect callback (the didSelect would be better a better choice). The callback will get called each time the tab bar switches.
Take a look at tabBarController:didSelectViewController: in UITabBarControllerDelegate. Implement that method in your delegate and do whatever updating you need to do in there.
Related
I am trying to use a variable (birthDateLabel) in two view controllers that are separated via a modal but use the same view controller class (CreateAccountViewController). The label works in the view that it is set in but after [self dismissViewControllerAnimated:YES completion:nil]; is run the varriable is reset, how can I retain it?
Order of operations:
The first instance of CreateAccountViewController is run
A button is tapped to go to a new instance of CreateAccountViewController but this instance has a different view with a UIDatePicker to set the birthDateLabel variable.
The birthDateLabel is set
The user taps done and dismissViewControllerAnimated is run
The app updates a UILabel on the first instance of CreateAccountViewController
Step 5 is what does not work, if I put the label on the view as the picker it works but when the modal is dismissed the variable is reset. How can I keep the variable set after the modal is dismissed? Or is my only option to create separate view controller classes?
I tried to do my best explaining this, but if you need me to explain it more just comment.
The standard way to do this is to use a delegate. The fact that your two controllers are both instances of the same class doesn't make any difference, other than they will both have a variable called birthDataLabel. The value of that variable is specific to each instance, just as it would be if these were of two different classes.
So, you should do it the right way, which is to create a delegate protocol in your second instance, and have the first one set itself as the delegate when it first presents the second one.
#rdelmar provides the most technically correct answer, but if it's just one value you could simply use nsuserdefaults. If the number begins to expand creating a delegate might be a smart choice.
The structure of my MainStoryboard is:
->Tab Bar Controller -> Navigation Controller -> View Controller (Search)
The behaviour I want to have is that when the user re-selects the Search tab, the UIScrollView on it scrolls to the top. I am unsure how to get the event from the TabBarController, however.
I've been looking at a lot of stuff about UITabBarDelegate, particularly:
- (void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item
I have, not quite managed to get this to work properly though. I am very unsure about how to go about setting the delegate (assuming that is the way it's done). I've tried hooking it up in IB, but it wouldn't let me. I also tried to get the UITabBar from the AppDelegate (after looking at some seemingly-related answers).
Any pointers will be greatly appreciated (unless they're null).
UITabBar *aTabBar = [UITabBarItem alloc] init];
....Any other modifications you want to make to aTabBar....
[aTabBar setDelegate:self]
Don't forget to add "<UITabBarDelegate>" to the "#interface" part of whatever object you're trying to designate as the delegate.
For my own code, I usually use some object that isn't the application delegate (as the app delegate is usually meant for application level events like "application is suspending" or "application is coming back into foreground"). If you add "<UITabBarDelegate>" to your Search view controller, make sure that whatever you do with the "didSelectItem" method is applicable only to the Search view controller. Otherwise instantiate some different object if you want to do actions on various view controllers based on which tab bar item is being displayed.
I have a pretty basic question. Assuming I have a UINavigationController set up for my app and I want to pass a value to the previous view when the user hits the "back" button in the UINavigationBar. I know I call popViewController:, but is there a way to pass a value back with it? Assuming there is (which there must be), what's the best way to do this?
Thanks!
What you should do in this case is think about the problem in a different way. You can create a delegate protocol on the view controller you want to pass information back from. This protocol can have any number of methods, at least one of which will look something like viewController:(MyViewController *)theViewController didSelectThisInformation:(NSString *)someInformation. When some action takes place on this view controller, it makes a call to its delegate (which conforms to the protocol you defined) and calls the appropriate method. When pushing this view controller, you would set its delegate property to the object you want to receive that information.
When I switch tabs in my tab bar application, one of my views needs to update because the user may have changed a preference that affects it. It is a UIViewController's view, but when the views switch, the viewDidLoad/Appear methods aren't called. Can this be solved using an NSNotification or any other way? Please give example code, especially for NSNotifications, as I am new to them.
You might want to peek at UITabBarControllerDelegate and tabBarController:didSelectViewController:. There you can determine how to handle the view change and whether you need to update the view based on the possible preference change.
tabBarController:didSelectViewController: you can implement this method in the appdelegate.
you will get the sxact root view controller at which yopu clicked . then you can update that view .
So, I developed a kind of drop down button class.
Let's call it DDButton.
I mainly export one function :
-(void) addButtonWithImage:(UIImage*)image andTarget:(id)target andSelector:(SEL)selector
which lets the user add another button to the drop down.
I will need to use DDButton in different screens of my app.
I would like to use it like:
DDButton* ddb = [[DDButton alloc] initWithFrame:rect];
[ddb addButtonWithImage....]
[ddb addButtonWithImage....]
My question is since I never subclassed UIView before how should I implement it, and how should I use it later ?
Do I use IB and create a stub UIView which I'll connect to the DDButton in the Identity Pane ?
if so , how exactly I instantiate the view later on.
Or,
Do I subclass UIView ? if so , what methods I should override ? Do you I setup my buttons in the initializer ? in LayoutSubView ? In drawRect ?
I would love to hear the best approach here.
Thanks!
Edit
Let's say I choose the IB way : I have a main button which I set regardless of the
addButtonWithImage() calls, actually all calls to addButtonWithImage just "append" to that button. I want to main button to be the size of the view, until other buttons are added and then the view grows appropriately. However, I want the size of the view to be chosen by the user at first...using setFrame I guess.
Meaning in the awakeFromNib I can't count on the frame size yet (it only take the xib size I assume). So where would I setup my main button ? LayoutSubView ? setFrame ? I'm not sure.
Add your view to the interface in IB as a UIView, then change the class in the identity pane. If you need to do initialization in code, use a -(void)awakeFromNib method. I would suggest setting up the buttons when they are added in addButtonWithImage....
I'd probably do a subclass, building views in code is a good thing to learn.
Override drawrect: to do any custom drawing you need to do, if you're just adding a UIImageview or something and doing positioning you could just override initWith...: and do your custom initialisations.