I have a navigation-based app and I use MBProgressHud like crazy in my app. I converted to ARC when it came out and I experienced a lot of app crashes and I could not understand why. I began using analyzer tools and saw that my memory consumption was through the roof. I went into all of my view controllers and overloaded their dealloc methods to include a write out to NSLog to tell me if they were being dealloced or not. To my surprise, none of the ViewControllers that used MBProgressHUD were being dealloced.
I am calling MBProgressHUD like this:
HUD = [[MBProgressHUD alloc] initWithView:self.navigationController.view];
[self.navigationController.view addSubview:HUD];
HUD.delegate = self;
HUD.labelText = #"Retrieving Signature";
[HUD showWhileExecuting:#selector(getSignature) onTarget:self withObject:nil animated:YES];
When done with MBProgressHUD, you need to clean up HUD by setting the delegate to Nil, removing from superview and finally setting the HUD to nil.
HUD.delegate = nil;
[HUD removeFromSuperview];
HUD=nil;
Related
I'm having some random crashes at this part of my code:
-(void) goBack {
[self performSelectorInBackground:#selector(addActivityIndicator) withObject:nil];
[self.navigationController popViewControllerAnimated:YES];
}
- (void)addActivityIndicator {
#autoreleasepool {
UIActivityIndicatorView *activityView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
UIBarButtonItem * barButton = [[UIBarButtonItem alloc] initWithCustomView:activityView];
[activityView startAnimating];
self.navigationItem.leftBarButtonItem = barButton;
}
}
When I want to exit the screen where these method exists, the other ViewController have to process some data. To inform the user that processing is occurring I add an activity indicator to the left button in my navigation bar.
The problem is that sometimes I get an exc_bad_access in addActivityIndicator method. The frequency is very random, sometimes the XCode shows the error at the end of #autoreleasepool, sometimes at the line self.navigationItem.leftBarButtonItem = barButton;
I imagine that sometimes my viewController is destroyed but the thread is still running and try to access the navigationItem of a object that don't exists anymore. But I'm not sure if that is the problem and I don't know how to fix it.
I'm using ARC in my project and this problem occurs in all iOS versions that I tested.
Please, anyone can explain me what is happening and how can I fix this?
Thanks.
You should never do UIKit stuff in the background.
By calling [self performSelectorInBackground:#selector(addActivityIndicator) withObject:nil]; you are updating the UI on a background thread. You should only ever update the UI on the main thread.
Edit
Based on your comment you are trying to have the UI update before the view pops. The way to do that would be:
[self addActivityIndicator]
[navigationController performSelector:#selector(popViewControllerAnimated:) withObject:[NSNumber numberWithBool:YES] afterDelay:0];
You could also look into dispatch_after
I'm using SDWebImagePrefetcher to prefetch a list of images off my plist.
I was editing the method trying to alloc a UIViewController which would have shown an MBProgressHUD HUD to indicate the progress.
Problem is that the HUD won't show in any way. Plus, SDWebImagePrefetcher is a NSObject and I don't really know where to init my custom UIViewController and the HUD, due it doesn't have any viewDidLoad or viewWillAppear methods.
I tried to do something like
MyCustomViewController *cv = [[MyCustomViewController alloc]init];
HUD = [[MBProgressHUD alloc]initInView:cv.view];
and didn't work.
I also tried to add an UIAlertView as subView of the viewController in order to see if it worked but it didn't work at all!
Any advice on where to init an UIViewController in a NSObject class in order to show an HUD on the allocated controller would be awesome.
If you want to display a MBProgressHUD from any class it's simple. Just add it to your application's keyWindow. This is the very top level window for your application and it easy to access from anywhere.
UIWindow *keyWindow = [[UIApplication sharedApplication] keyWindow];
MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:keyWindow animated:YES];
hud.labelText = #"Loading";
And when you want to hide the MBProgressHUD just use
[hud hide:YES];
Make sure you wait to access the keyWindow until your app's main window has been set up. This occurs at launch. If it is setup programmatically it is in your AppDelegate by calling [window makeKeyAndVisible].
I apologize in advance for the n00b question. I am just getting started w/ iOS!
I am trying to push a webViewController onto a navigation controller.
mudWebViewController *webViewController = [[mudWebViewController alloc] initWithNibName:nil bundle:nil];
[[webViewController webView] setDelegate:webViewController];
[[self navigationController] pushViewController:webViewController animated:YES];
But this doesn't seem to work, as I don't see any of the logs in the delegate messages.
If I set the delegate in the viewDidLoad: method, it works fine.
I guess the webView doesn't actually exist at that point, but why? If I initialize the controller, shouldn't the webView be initialized too?
Is viewDidLoad: the right place to be setting up this stuff?
initWithNibName should be not nil, since you obviously are using a nib file to build the view, else you have to create the view in code, which you don't
mudWebViewController *webViewController = [[mudWebViewController alloc] initWithNibName:#"webViewController" bundle:nil];
[[self navigationController] pushViewController:webViewController animated:YES];
Also any delegates should be set either from the Interface builder or from the view itself in the viewDidLoad delegate and not from the previous class, as the object might not been yet initialized in the code so it can fail to set the delegate properly.
I have a class with a viewDidLoad method and an artworkInfo method as follows:
-(void)viewDidLoad {
mainDelegate = (AppDelegate*)[[UIApplication sharedApplication]delegate];
[super viewDidLoad];
}
-(void)artworkInfo:(NSNumber *)pos{
mainDelegate = (AppDelegate*)[[UIApplication sharedApplication]delegate];
[self.image setImage:(UIImage *)[[mainDelegate.mapAnnotations objectAtIndex:0]image]];
}
the mainDelegate thing is to gain access to the appDelegate where an array is stored, but anyway, with the "[self.image setImage...]" command where it is, the image on the app does not appear, but when I copy that exact line of code into the viewDidLoad method, it shows up like it should. I know that the artworkInfo method is being called because I debugged it and it goes through, so I can't figure out why the command would not be doing anything it's current method while it will in the viewDidLoad...?
Also, here is where the method is called and this new view is loaded from another class:
infoPage *info = [[infoPage alloc] initWithNibName:#"infoPage" bundle:nil];
info.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
[self presentModalViewController:info animated:YES];
infoPage *myInfoPage = [[infoPage alloc] init];
[myInfoPage artworkInfo:position];
[info release];
OH, I see the problem. You're instantiating 2 different infoPage classes.
Change this:
infoPage *info = [[infoPage alloc] initWithNibName:#"infoPage" bundle:nil];
info.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
[self presentModalViewController:info animated:YES];
infoPage *myInfoPage = [[infoPage alloc] init];
[myInfoPage artworkInfo:position];
[info release];
to this:
infoPage *info = [[infoPage alloc] initWithNibName:#"infoPage" bundle:nil];
info.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
[self presentModalViewController:info animated:YES];
[info artworkInfo:position];
[info release];
Ok detailed answer. In order to understand why this image is not displaying properly you have to first look at how Runloops work in Objective C.
While viewDidLoad is the method that is called when a view is loaded and it is technically also called before a view is displayed and it's view objects initialized. Since presentModalViewController is an animation there is actually some threading going on in the works.
viewDidLoad gets called before the animation is created for the presentModalView. This initializes your objects. However, due to some of the inner workings of UI Kit some processes are loaded off into a thread. When they complete they run callback methods on the main UI thread.
Since presentModalViewController is a non-blocking method your artworkInfo method gets added to the mainRunLoop before the initializer form thread adds its callback methods to the main run loop. The best approach would be to have both a UIImage property of your viewController and a UIImageView.
set the value of UIImage by calling artworkInfo BEFORE the presentModalViewController method.
in your ViewDidLoad go ahead and set the value of your UIImageView
[self.imageView setImage:self.image];
Problem solved.
This seems pretty straight forward.
So you initialize your nib and try to call your method artwork before the nib is fully loaded. <-- This is not working for you.
Then you do additional initialization by overrider viewDidLoad per the doco where the nib is loaded <-- This is working for you
So the answer is, when you call setImage before your nib is loaded, then there is nothing to set the image to. When you call setImage in viewDidLoad your nib is loaded and then things should work just fine.
I hope this explains it a bit.
I feel like I don't understand something fundamental here. I've been working on memory management in my app while using Instruments to check out live allocations. I have a modal view controller (settingsViewController) that has an image for a background. One thing I noticed was that even after settingsViewController dealloc is called, there still is a live Malloc 520 KB, ImageIO is the responsible library. I'd expect live memory to drop back down after dismissing settingsViewController. Is the UIImageView still hanging around somewhere?
Here is how I load the image in viewDidLoad, as well as dismiss the view controller when I'm finished.
- (void)loadView {
[super loadView];
////// background ////////
UIImageView *background = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"settings_background.png"]];
[self.view addSubview:background];
[background release];
//////////////////////////
}
- (void)viewDidLoad {
[super viewDidLoad];
///////// done button //////////
UIBarButtonItem *done = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:#selector(doneButtonPressed)];
self.navigationItem.leftBarButtonItem = done;
[done release];
////////////////////////////////
}
- (void) doneButtonPressed {
[self dismissModalViewControllerAnimated:YES];
}
- (void)dealloc {
NSLog(#"settingsViewController dealloc"];
[super dealloc];
}
At this point, this is all that is in the settingsViewController, so no need to do anything special in dealloc, right? Here is how I'm showing testViewController in the rootViewController.
- (void) loadSettingsView {
SettingsViewController *settingsViewController = [[SettingsViewController alloc] init];
UINavigationController *settingsNavigationController = [[UINavigationController alloc] initWithRootViewController:settingsViewController];
[self presentModalViewController:settingsNavigationController animated:YES];
[settingsViewController release];
[settingsNavigationController release];
}
I'd like to make sure I understand what is going on before moving forward. I have several different modal view controllers, each with a different image as a background. Since each one creates a Malloc 520 KB, I end up using 2-3 MB of precious memory for no good reason. What is holding on to that 520 KB?
When you use the +[UIImage imageNamed:] method, the framework caches the image data for you. That's why you see it hold onto some memory even after your view is released. If you're working in the simulator and you want to see it release that memory, send the simulator a memory warning after you've dismissed your view. The image framework should then release the cached image data.