I have 5 view controllers, which are in a navigation controller hierarchy. When I reach my last view controller, there's a button that lets me go back to the "Home" view controller (named CardWalletViewController) which is a table view controller. Here's the method I have in my last VC (PointsResultsVC)
- (IBAction)homePressed:(id)sender {
NSArray *VCs = [self.navigationController viewControllers];
[self.navigationController popToViewController:[VCs objectAtIndex:0] animated:YES];
}
CardWalletVC's cells is being filled up by values coming from the saved instances of a Card in NSUserDefaults and it works fine.
Now, what I want is to update the value in my CardWalletViewController, which is the points of a card coming from my PointsResultsVC. Note that this points is saved in NSUserDefaults.
Upon the process of trying to update of the value shown in my CardWalletVC, I placed [self.tableView reloadData]; inside -viewDidLoad, -viewWillAppear, and -viewDidAppear of the said class. I tried placing it one by one in each of this methods, yet it doesn't seem to work.
Advice Please.
EDIT: problem solved
This one served as my guide Save data from one tab and reloadData in another tab.
And as I have discovered, -viewDidLoad of a certain class will only be called once, all throughout runtime of app. Whereas -viewWillAppear, it will be called every time the view appears.
So, I just moved the way I am loading the values saved in NSUserDefaults from -viewDidLoad to -viewWillAppear. Also, inside -viewWillAppear I placed the [self.tableView reloadData]. Then there, problem solved.
There's a lot of things that could be going wrong so you'll need to provide more info to narrow it down.
First of all, viewDidLoad will not be called so you can remove it from here. Both viewWillAppear and viewDidAppear will be called, so you only need it one of these 2 methods.
Next, you need to determine what the actual issue is.
1 - is self.tableView a proper reference to the table? Are you properly maintaining the reference?
2 - is the table actually reloading but using the old data, or is it not reloading at all? You can log the willDisplayCell method to see what is going on when the view appears.
With that info, the root cause can be narrowed down to a solvable problem.
Related
Ok I am trying to refresh the tab content of each of my tabs after a web call has been made, and I have tried soo many different methods to do this that I have lost count. Could someone please tell me how this is possible?
The web call just calls JSON from a server and uses it to update the content of the tabs. For testing purposes I have a button set up inside my settings class. Settings class is a view within the home tab which has a button called refresh. When clicked this takes JSON stored on the device which is different to the one called from the web call on application start up. This saves me having to change the JSON on the server.
I will take you through some of the techniques I have tried and would be grateful if someone could tell me what I am doing wrong.
I tried making an instance of the class and calling the refresh method like this
DashboardVC *db = [[DashboardVC alloc] init];
[db refreshMe];
The refresh method in dashboard class is this
-(void) refreshMe
{
[self loadView];
[self viewDidLoad];
}
However no luck. This method will work if I call it inside the Dashboard class, but wont work if I call it from another class. I think it is become I am instantiating a new class and calling refresh on that. So I dropped that technique and moved onto the next method
This loops through all the tabBars and changes the tabTitles without any issues, so it I know it is definitely looping through the ViewControllers properly.
I also tried every varient of the view methods like ViewDidAppear, viewWillAppear etc, no luck.
I also tried accessing the refreshMe method I made in the dashBoard class through the tabController like this
[[[self.tabBarController viewControllers] objectAtIndex:0] refreshMe];
But again no luck, this just causes my application to crash.
I read through this guide
https://developer.apple.com/library/ios/#documentation/WindowsViews/Conceptual/ViewControllerPGforiOSLegacy/TabBarControllers/TabBarControllers.html
on the apple website but it doesn't seem to cover how to refresh individual tab content.
All I want is to have each individual tab refresh its content after the web call is made, and have spent ages trying to figure this out, but nothing is working.
So would be very grateful if someone could show me what I am doing wrong?
Thanx in advance....
EDIT:
Expand on what I have tried
After discussion with Michael I realised you should never call loadView as against Apple guidelines. So I removed any references to LoadView. I have now placed a method in all the main ViewControllers called RefreshMe which sets up the views, images texts etc in the class. And this method is placed inside the ViewDidLoad. Now I want to be able to call these methods after a web call has taken place, so effectively refreshing the application.
My viewDidLoad now looks like this in all my the main classes.
- (void) viewDidLoad {
[super viewDidLoad];
[self refreshMe];
}
And then the refreshMe method contains the code which sets up the screen.
The JSON data pulled from the web call will set up the content of each of the 5 tabs, so need them all to be refreshed after web call.
I tried looping through the viewControllers and calling viewDidLoad, which should in turn call the refreshMe method which sets up the class, however nothing happens. Code I used was this
NSArray * tabBarViewControllers = [self.tabBarController viewControllers];
for(UIViewController * viewController in tabBarViewControllers)
{
[viewController viewDidLoad];
}
For the time being I have also included
NSLog(#"Method called");
in the viewDidLoad of each class to test if it is being called. However the message is only being printed out when I first load the application or if I re-enter the application. This method should be called after I click the refresh button in the settings screen but it isn't and I have no idea why.
Anyone have any idea why this is not working?
From the question and your comments, it sounds like there are at least two problems:
You're having trouble accessing the view controllers managed by your app's tab bar controller.
You seem to be working against the normal operation of your view controllers.
The first part should be straightforward to sort out. If you have a pointer to an object, you can send messages to that object. If the corresponding method doesn't execute, then either the pointer doesn't point where you think it does or the object doesn't have the method that you think it does. Let's look at your code:
NSArray * tabBarViewControllers = [self.tabBarController viewControllers];
for(UIViewController * viewController in tabBarViewControllers)
{
[viewController viewDidLoad];
}
This code is supposed to call -viewDidLoad on each of the view controllers managed by some tab bar controller. Leaving aside the wisdom of doing that for a moment, we can say that this code should work as expected if self.tabBarController points to the object that you think it does. You don't say where this code exists in your app -- is it part of your app delegate, part of one of the view controllers managed by the tab bar controller in question, or somewhere else? Use the debugger to step through the code. After the first line, does tabBarViewControllers contain an array of view controllers? Is the number of view controllers correct, and are they of the expected types? If the -viewDidLoad methods for your view controllers aren't being called, it's a good bet that the answer is "no," so figure out why self.tabBarController isn't what you think.
Now, it's definitely worth pointing out (as Michael did) that you shouldn't be calling -viewDidLoad in the first place. The view controller will send that method to itself after it has created its view (either loaded it from a .xib/storyboard file or created it programmatically). If you call -viewDidLoad yourself, it'll either run before the view has been created or it'll run a second time, and neither of those is helpful.
Also, it doesn't make much sense to try to "refresh" each view controller's view preemptively. If your app is retrieving some data from a web service (or anywhere else), it should use the resulting data to update its model, i.e. the data objects that the app manages. When a view controller is selected, the tab bar controller will present its view and the view controller's -viewWillAppear method will be called just before the view is displayed. Use that method to grab the data you need from the model and update the view. Doing it this way, you know that:
the view controller's view will have already been created
the data displayed in the view will be up to date, even if one of the other view controllers modified the data
you'll never spend time updating views that the user may never look at
Similarly, if the user can make any changes to the displayed data, you should ensure that you update the model either when the changes are made or else in your view controller's -viewWillDisappear method so that the next view controller will have correct data to work with.
Instead of refreshing your view controllers when updating your tab bar ordering, why not simply refresh your views right before they will appear by implementing your subclassed UIViewController's viewWillAppear: method?
What this means is that each time your view is about to appear, you can update the view for new & updated content.
I have an app that uses a UITablewView and in that TableView there is an NSMutableArray that holds the data to be displayed in the TabelView.
The problem is in my TableView Controller I use:
[[self tableView] reloadData]
To reload the TableView data and it works fine for a couple of times but doesn't work on the 3rd time and instead it changes the array count in a weird way.
Now I read similar question here and most likely I have 2 instances of the TableView or the TableViewController but I can't figure out how to troubleshoot this? How to detect if there are 2 instances of the object and fix that?
EDIT: Here is a pic how my navigation goes
So the 1st round of going from ScrollView to TableView things show up correctly. Then I go to UIView and back to TableView and it's working fine. So I go back all the way to ScrollView and back again to TableView and it's good.
But when I go to the UIView for this time then back to TableView this problem happens. TableView doesn't display the changes. So I put a breakpoint just before [[self tableView] reloadData] and found out that the array _displayedObjetcs gets its count changed. -1 actually. see the following screen shots b4 and after I step over the reloadData
and then
My immediate thought is that your array is not being retained properly, by your application. Your "weird" count is probably a number like 234791..., which is highly indicative of an array that has been released incorrectly. Therefore, I would check how your are retaining and releasing this array.
However, without more posted code, it is impossible to help you further.
I have data being refreshed in a modalViewController and when that data gets refreshed, the parent controller needs to refresh its data as well. I tried doing a [tableView reloadData]; but it didn't work properly since the actual array values aren't being refreshed. Is there a way for me to reload a controller without the user seeing any animation?
Thanks for any help!
Are you refreshing the data off the main thread? If so, you need to call the reloadData method using the following method:
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait
So for a tableView it would be something like:
[tableView performSelectorOnMainThread:#selector(reloadData) withObject:nil waitUntilDone:NO];
The underlying view can get released while the modal view is showing, so you shouldn't try to modify it directly. Instead, you can use the viewWillAppear: method on the main view controller to make any necessary updates.
I'm not sure what you mean that "the actual array values aren't being refreshed". How the two view controllers exchange data depends a lot on what you are trying to accomplish. If the modal view is only used in one place, the main controller can access its properties directly. Or maybe you want a dedicated class to hold the state... Again, depends on the context.
I have a UITableView which is populated by an array, I have a button on the navigaton bar which (when pressed) adds an item to the array and calls [self.tableView reloadData] in the UITableView. This results in numberOfRowsInSection being called and returning the correct number of rows (the number of items in the array) BUT doesn't call cellForRowAtIndexPath.
I have created a new navigation based application to try and find a solution but have exactly the same problem!
If anyone knows the answer it would be greatly appreciated, i've been tearing what's left of my hair out for the last day!
I have put the source for the test project up on my site at www.sofaracing.com/Downloads/Test3.zip
Works for me! ;)
In MainWindow.xib, You added an object Root View Controller (that's not part of the Navigation Controller) - Delete it, not necessary. Then connect outlet refreshFriendsList to the Bar Button of the NavigationItem of RootViewController. Wha-la, magic!
BTW: You may need to clean up the warning. And you might want to think about creating a class for your data model instead of using UIApplication sharedApplication.
I quickly debugged your test app. I couldnt't spot the root cause, but it seems that you have two different table views due some mess up in Interface Builder setup.
If you initialize original array with an item, cellForRowAtIndexPath is correctly called. If you examine self.tableView instance in this call and later in subsequent calls to refreshFriendsList, self.tableView points to a different instance.
2009-05-17 14:33:07.591 Test3[33580:20b] cellForRowAtIndexPath 0
2009-05-17 14:33:07.594 Test3[33580:20b] self.tableView: <UITableView: 0x52b9b0>
2009-05-17 14:42:36.810 Test3[33762:20b] numberOfRowsInSection: tableView <UITableView: 0x53bcd0>
I have a RootViewController and a SubViewController. I traverse the views in either direction. The RootViewController is a UITableView SubClass. Depending upon the row selected I want to change the title of the subview using self.navigationItem.title = [chunks objectAtIndex:1];
It works when the subview is first time loaded. But when I return to the RootViewController and load the subview again the previous title persists.
Any ideas what am I missing out on?
In your particular case, you probably want to set your title in viewWillAppear: so that the title gets set every time the view comes on the screen.
I just tried it in an app of mine. When I set the title using
self.navigationItem.title = #"Foo"
the name in the navigation bar changes instantly. I think you have a bug somewhere else that you code is only getting called the first time you invoke your SubViewController. Stick a break point on that line and see if it actually gets called a second time. Or perhaps [chunks objectAtIndex:1] is always returning the same string.
Or perhaps I'm not understanding your question. As far as I can tell it does work like you are expecting it to.
I guess you are trying to change the title in the viewDidLoad method. The viewDidLoad is called only the first time the view is loaded. In case you are reusing the same viewcontroller's instance, viewDidLoad will be called only once.
Instead try setting the title in viewWillAppear method. This method is called every time the view is going to be displayed. That should work.