It looks like this topic comes up a lot. I read through several answers but none were the same case as mine so please excuse me if you've seen similar before.
All of my UIViewControllers are being controlled by UINavgationController. On the first UIViewController (SMOnboardingPhotoMarketingViewController), I call into my keychain wrapper class to see if there is anyone logged in (app resuming). If so I call the segue to go to my main logged in screen (SMThumbnailViewController), where I'm getting the error message: Unbalanced calls to begin/end appearance transitions for .
I have examined all of the view controller life-cycle calls to ensure that I'm calling [super method] if I over-rode them. Done.
Other than that this is just a standard push type segue for all transitions. I don't understand what is so different about this call to a segue than all the others that are triggered by button actions. Here is the code from my first view controller:
-(void)viewDidAppear:(BOOL)animated{
[super viewDidAppear:animated];
[self loadScrollViewContent];
__weak SMOnboardingPhotoMarketingViewController *weakSelf = self;
[SMAuthentication validateStoredTokenWithCompletion:^(BOOL valid) {
if(valid){
NSLog(#"Logged in. Continue to thumbs page");
[weakSelf performSegueWithIdentifier:kSeguePhotoMarketingToThumbnails sender:self];
}
else{
[SMAuthentication logOut];
NSLog(#"invalid credentials stored. User must log in ");
}
}];
}
I've noticed that in my main view controller (the one that the above code navigates to), viewDidLoad is called, but viewDidAppear is never called. What could cause such an imbalance?
Edit: Adding info. I should state taht if I move the segue call to the outside of that block, the transition goes as normal with no error. Example:
// I know this is ugly. It is for testing only
-(void)viewDidAppear:(BOOL)animated{
[super viewDidAppear:animated];
[self loadScrollViewContent];
__block BOOL complete = NO;
__block BOOL isValid = NO;
[SMAuthentication validateStoredTokenWithCompletion:^(BOOL valid) {
if(valid){
NSLog(#"Logged in. Continue to thumbs page");
isValid = YES;
}
else{
[SMAuthentication logOut];
NSLog(#"invalid tokens stored. User must log in ");
}
complete = YES;
}];
while (!complete) {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
}
if(isValid){
[self performSegueWithIdentifier:kSeguePhotoMarketingToThumbnails sender:self];
}
}
You probably have implemented the following ViewController custom container methods:
- (void)endAppearanceTransition
- (void)beginAppearanceTransition:(BOOL)isAppearing animated:(BOOL)animated
I once written and forgot them in a base class and they messed up the whole appearance forwarding to child controllers when using storyboards.
Related
I have a button with this:
- (IBAction)themeBtnAction:(id)sender
{
NSString *language = [[OnlineStore sharedStore]getTheLanguage];
[[OnlineStore sharedStore]getTheThemeBaseGuides:language callback:^{
[self performSegueWithIdentifier:#"from main to themecategory" sender:self];
}]
}
But when user happens to doubletap the button it causes a crash. Probably because next viewcontroller is being loaded twice onto the heap (my guess) and the error message I get when I try to return with UINavigationController pop from that second UIViewControlleris: Unbalanced calls to begin/end appearance transitions for <MySecondViewController: 0xb257b80>.
How can I do to prevent this?
I have tried to put it inside callback within:
if ([NSStringFromClass([[viewControlles lastObject] class]) isEqualToString: #"MainViewController"]) {
and I have tried to do the callback within the selector goToNextView in the btn
[self performSelector:#selector(goToNextView) withObject:self afterDelay:1.0];
No luck.
Any suggestions. And please ask if this is unclear since I am a bit tired and just about to try to sleep now :)
You can ignore user interaction until the view controller disappears:
- (IBAction)themeBtnAction:(id)sender
{
NSString *language = [[OnlineStore sharedStore]getTheLanguage];
[[OnlineStore sharedStore]getTheThemeBaseGuides:language callback:^{
[[UIApplication sharedApplication] beginIgnoringInteractionEvents];
[self performSegueWithIdentifier:#"from main to themecategory" sender:self];
}]
}
- (void)viewDidDisappear:(BOOL)animated
{
[[UIApplication sharedApplication] endIgnoringInteractionEvents];
}
Or just disable user interaction on the button in a similar manner:
button.userInteractionEnabled = NO;
...
button.userInteractionEnabled = YES;
I have two UITableViewControllers A and B, and this is what I'm trying to do when I click on a table view cell in A:
Prepare to segue from A to B by setting some of B's variables from A.
Perform segue from A to B.
B appears.
Display a "Loading" activity indicator with [MBProgressHUD][1].
In a background task, retrieve data from a URL.
If an error occurs in the URL request (either no data received or non-200 status code), (a) hide activity indicator, then (b) display UIAlertView with an error message
Else, (a) Reload B's tableView with the retrieved data, then (b) Hide activity indicator
However, this is what's happening, and I don't know how to fix it:
After clicking a cell in A, B slides in from the right with an empty plain UITableView. The MBProgressHUD DOES NOT SHOW.
After a while, the tableView reloads with the retrieved data, with the MBProgressHUD appearing very briefly.
The MBProgressHUD immediately disappears.
There doesn't seem to be an error with the way the background task is performed. My problem is, how do I display the MBProgressHUD activity indicator as soon as my B view controller appears? (And actually, how come it's not showing?) Code is below.
A's prepareForSegue
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
B *b = (B *)[segue destinationViewController];
// Set some of B's variables here...
}
Relevant methods in B
- (void)viewDidAppear:(BOOL)animated {
[self startOver];
}
- (void)startOver {
[self displayLoadingAndDisableTableViewInteractions];
[self retrieveListings];
[self.tableView reloadData];
[self hideLoadingAndEnableTableViewInteractions];
}
- (void)displayLoadingAndDisableTableViewInteractions {
MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];
hud.labelText = #"Loading";
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
self.tableView.userInteractionEnabled = NO;
}
- (void)hideLoadingAndEnableTableViewInteractions {
[MBProgressHUD hideHUDForView:self.view animated:YES];
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
self.tableView.userInteractionEnabled = YES;
}
- (void)retrieveListings {
__block NSArray *newSearchResults;
// Perform synchronous URL request in another thread.
dispatch_sync(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
newSearchResults = [self fetchNewSearchResults];
});
// If nil was returned, there must have been some error--display a UIAlertView.
if (newSearchResults == nil) {
[[[UIAlertView alloc] initWithTitle:#"Oops!" message:#"An unknown error occurred. Try again later?" delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil] show];
} else {
// Add the retrieved data to this UITableView's model. Then,
[self.tableView reloadData];
}
}
- (NSArray *)fetchNewSearchResults {
// Assemble NSMutableArray called newSearchResults from NSURLConnection data.
// Return nil if an error or a non-200 response code occurred.
return newSearchResults;
}
I think you have to call [self hideLoadingAndEnableTableViewInteractions]; after newSearchResults = [self fetchNewSearchResults]; You are retrieving data in another thread which means -startOver will continue executing after calling [self retrieveListings]; and will hide the HUD right away. Also because you are updating the display you have to make sure you are doing that on the main thread. See example
dispatch_async(dispatch_get_main_queue(), ^{
//update UI here
});
When B appears, it displays a plain and empty UITableView, but does not display the MBProgressHUD even if the task does begin in the background (and yet, the MBProgressHUD is called to show before that). Hence, my solution is to show the MBProgressHUD in viewDidLoad, which precedes viewWillAppear.
- (void)viewDidLoad {
// ...
[self displayLoadingAndDisableUI];
}
I set up two additional boolean properties to B--one in .h, called shouldStartOverUponAppearing, and one in a class extension in .m, called isLoadingAndDisabledUI. In startOver, I added the following lines:
- (void)startOver {
if (!self.isLoadingAndDisabledUI) {
[self displayLoadingAndDisabledUI];
}
}
The check is done so that startOver doesn't display another MBProgressHUD when it has already been displayed from viewDidLoad. That is because I have a third view controller, called C, that may call on B's startOver, but doesn't need to call viewDidLoad just to display the MBProgressHUD.
Also, this is how I defined viewDidAppear:
- (void)viewDidAppear:(BOOL)animated {
if (self.shouldStartOverUponAppearing) {
[self startOver];
self.shouldStartOverUponAppearing = NO;
}
}
This way, startOver will only be invoked IF B appeared from A. If B appears by pressing "Back" in C, it will do nothing and only display the old data that was there.
I think that this solution is FAR from elegant, but it works. I guess I'll just ask for a better approach in a separate SO question.
I have used a common method for MBProgressHUD.
#import "MBProgressHUD.h" in AppDelegate.h also following methods.
- (MBProgressHUD *)showGlobalProgressHUDWithTitle:(NSString *)title;
- (void)dismissGlobalHUD;
In AppDelegate.m add following methods.
- (MBProgressHUD *)showGlobalProgressHUDWithTitle:(NSString *)title {
[MBProgressHUD hideAllHUDsForView:self.window animated:YES];
MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.window animated:YES];
hud.labelText = title;
return hud;
}
- (void)dismissGlobalHUD {
[MBProgressHUD hideHUDForView:self.window animated:YES];
}
How to use?
AppDelegate *appDel = (AppDelegate *)[[UIApplication sharedApplication]delegate];
//Show Indicator
[appDel showGlobalProgressHUDWithTitle:#"Loading..."];
//Hide Indicator
[appDel dismissGlobalHUD];
Hope this helps.
I am trying to implement the SVProgressHUD progress activity indicator. I copied the class from the [demo].1
My app loads up but the activity indicator doesn't show up. This is my first time trying to use one of these, so any help would be appreciated.
Here is the code:
#import "SVProgressHUD.h"
#implementation QuotesAppDelegate
- (void)startLoading
{
//call this in your app delegate instead of setting window.rootViewController to your main view controller
//you can show a UIActivityIndiocatorView here or something if you like
[SVProgressHUD show];
[self performSelectorInBackground:#selector(loadInBackground) withObject:nil];
}
- (void)loadInBackground
{
//do your loading here
//this is in the background, so don't try to access any UI elements
[self populateFromDatabase];
[SVProgressHUD dismiss];
[self performSelectorOnMainThread:#selector(finishedLoading) withObject:nil waitUntilDone:NO];
}
- (void)finishedLoading
{
//back on the main thread now, it's safe to show your view controller
[window addSubview:[navigationController view]];
[window makeKeyAndVisible];
}
- (void)applicationDidFinishLaunching:(UIApplication *)application {
[self copyDatabaseIfNeeded];
[self startLoading];
}
For anyone else having a similar problem, this can also happen because you have a long loop or a piece of code that takes a long time to execute. If this happens, your progress bar wont be shown until after the loop, which kind of defeats the purpose.
To solve this issue you need to you this:
- (void)performSelectorInBackground:(SEL)aSelector withObject:(id)arg
Basically your code would look something like this:
- (IBAction)submitPost:(id)sender {
//now we show the loading bar and submit the comment
[SVProgressHUD showWithStatus:#"Submitting post" maskType:SVProgressHUDMaskTypeGradient];
SEL aSelector = #selector(submitDataOfPost);
[self performSelectorInBackground:aSelector withObject:sender];
}
This will basically load the progress bar, and in a background thread, the method you want to execute will be called. This makes sure that the UI is updated (shows the progress hud) at the same time that your code is executed.
First of all you were not adding your SVProgressHUD to the view.
If your class inherited from UIViewController then [self.view addSubview:]; or if your class is simple UIView then [self addSubView:];
I do not understand your requirement but as far as i can understand through your code that you are showing [SVProgressHUD show]; in your startLoading method and then you are calling loadInBackground method in that method where you are hiding your hud using [SVProgressHUD dismiss];
I will suggest you to trace it by using breakpoint and figure it out.
I had the same problem. When I changed a version of SVProgressHUD to the later one the problem disappeared. My current version supports ARC.
=>
(IBAction)fetchData:(id)sender
{
[SVProgressHUD showWithStatus:#"Loading..." maskType:SVProgressHUDMaskTypeGradient];
[self performSelectorOnMainThread:#selector(getDataFromSomeWhere) withObject:nil waitUntilDone:NO];
}
=>
(void)getDataFromSomeWhere
{
//Do your data populating here. and dismiss the ProgressHud.
[SVProgressHUD dismiss];
}
so basically in my app delegate i have a navigation.controller
This navigation controller has a view of a class named MainScreen.
In MainScreen.m , i have a IBAction which will bring me to a SelectionScreen.m page by pushing it. here is the coding for it
SelectionScreen *aSelectionScreenViewController = [[SelectionScreen alloc]initWithNibName:#"SelectionScreen" bundle:nil];
[self.navigationController pushViewController:aSelectionScreenViewController animated:YES];
[aSelectionScreenViewController release];
So how do i check if my current navigationController.view = this selectionscreen.view?
The reason for checking which current view it is, is because when i receieve a push notification, i would want to automatically switch to this SelectionScreen.m page and invoke some methods within it. But this checking can only be done in the appDelegate because the didReceiveRemoteNotification method is located in there.
This is how i'm doing it
for example if you have three ViewControllers ,and any of those have possibility to be pushed by NavigationController:
ViewControllerA
ViewControllerB
ViewControllerC
Then what you need to do is:
-(void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
{
if ([[self.navigationController topViewController] isKindOfClass:[ViewControllerA class]]) {
//do sth
}
if ([[self.navigationController topViewController] isKindOfClass:[ViewControllerB class]]) {
//do sth
}
if ([[self.navigationController topViewController] isKindOfClass:[ViewControllerC class]]) {
//do sth
}
}//end of code
One way is to save selectionScreenViewController as a property of your app delegate, then:
if (self.navigationController.topViewController == self.selectionScreenViewController) {
//...
}
else {
//...
}
Hey guys, i did it in a simple way. In every view controller i had, i removed all objects and assigned an object to an array in the appdelegate. So this way, everytime i go to a new view, the value is different.
So in appdidrecieveremotenotification, i can check that array and decide on what to do accordingly.
Its just a simple way of checking.
I've been searching around but unfortunately have had no luck.
My app requires the user to sign in/sign up the first time he or she launches the app. I know how to determine first launch (using NSUserDefaults) but whenever I try to present the modal containing the sign in/ sign up controls, nothing happens.
Here's what I have:
-(void)viewDidLoad {
[self showLogin];
[super viewDidLoad];
}
-(void)showLogin {
FlipsideViewController *controller = [[FlipsideViewController alloc] initWithNibName:#"AccountView" bundle:nil];
controller.delegate = self;
controller.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
[self presentModalViewController:controller animated:YES];
[controller release];
}
However, nothing happens. The main view just loads as normal. Any help is greatly appreciated.
-Giles
[UPDATE]
Fixed simply by using..
-(void)viewDidAppear:(BOOL)animated
{
}
instead of
-(void)viewDidLoad
{
}
Thanks anyway!
/idiocy
I had the same issue and ended up using viewDidAppear as well. The only problem with the viewDidAppear approach is that if you load other UIViewControllers on top, then reshow the base, then your setup code gets called over and over. I ended up having to add a boolean value (initialised to YES) to this view controller and check that value before deciding what to do. Hope this helps someone...
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:(BOOL)animated];
if(justLaunched)
{
justLaunched = NO;
if(settingsFileExists)
{
[self displayMainView];
}
else
{
[self displaySetupView];
}
}
}
How about using performSelector:withObject:afterDelay in the viewDidLoad function? That's how I do it, with a short delay of 0.1s.
And invoking this in the viewDidLoad isn't very safe : the sequence viewDidLoad / viewDidUnload can occur at runtime when the iPhone needs to release some views in order to get back some free memory.
The side effect of such sequence would be that your login controller would be shown...
As you said the viewDidAppear looks better but not simply put it at the end of the appDidFinishedLaunching the delegate of your UIApplication?