The appearance of the UIView crashes application

Question

I basically click on the UIView from the UITableViewController, and all it contains is a UIWebView. However, when I remove the UIView to return to the UITableView, the application crashes.

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { // Navigation logic may go here. Create and push another view controller. if (indexPath.row == websiteCell) { NSString *urlPath = [NSString stringWithFormat:@"http://%@", exhibitor.website]; WebViewController *webViewController = [[WebViewController alloc] initWithURLString:urlPath]; // Pass the selected object to the new view controller. [self.parentViewController presentModalViewController:webViewController animated:YES]; [webViewController release]; } 

}

If I comment on [release WebViewController], the application will not work, but I know it will be a leak.

Below is the web browser code:

 #import "WebViewController.h" @implementation WebViewController @synthesize webBrowserView; @synthesize urlValue; @synthesize toolBar; @synthesize spinner; @synthesize loadUrl; -(id)initWithURLString:(NSString *)urlString { if (self = [super init]) { urlValue = urlString; } return self; } #pragma mark WebView Controls - (void)goBack { [webBrowserView goBack]; } - (void)goForward { [webBrowserView goForward]; } - (void)reload { [webBrowserView reload]; } - (void)closeBrowser { [self.parentViewController dismissModalViewControllerAnimated:YES]; } #pragma end // Implement viewDidLoad to do additional setup after loading the view, typically from a nib. - (void)viewDidLoad { [super viewDidLoad]; CGRect contentRect = self.view.bounds; //NSLog(@"%f", contentRect.size.height); float webViewHeight = contentRect.size.height - 44.0f; // navBar = 44 float toolBarHeight = contentRect.size.height - webViewHeight; // navigation bar UINavigationBar *navBar = [[[UINavigationBar alloc] initWithFrame:CGRectMake(0, 20, contentRect.size.width, 44)] autorelease]; navBar.delegate = self; UIBarButtonItem *doneButton = [[[UIBarButtonItem alloc] initWithTitle:@"Done" style:UIBarButtonItemStyleDone target:nil action:@selector(closeBrowser)] autorelease]; UINavigationItem *item = [[[UINavigationItem alloc] initWithTitle:@"CEDIA10"] autorelease]; item.leftBarButtonItem = doneButton; [navBar pushNavigationItem:item animated:NO]; [self.view addSubview:navBar]; // web browser webBrowserView = [[UIWebView alloc] initWithFrame:CGRectMake(0, 64, contentRect.size.width, webViewHeight)]; webBrowserView.delegate = self; webBrowserView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight; webBrowserView.scalesPageToFit = YES; [self.view addSubview:webBrowserView]; // buttons UIBarButtonItem *backButton = [[[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"arrowleft.png"] style:UIBarButtonItemStylePlain target:self action:@selector(goBack)] autorelease]; UIBarButtonItem *fwdButton = [[[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"arrowright.png"] style:UIBarButtonItemStylePlain target:self action:@selector(goForward)] autorelease]; UIBarButtonItem *refreshButton = [[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh target:self action:@selector(reload)] autorelease]; UIBarButtonItem *flexSpace = [[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil] autorelease]; UIBarButtonItem *fixSpace = [[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace target:nil action:nil] autorelease]; [fixSpace setWidth: 40.0f]; spinner = [[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite] autorelease]; [spinner startAnimating]; UIBarButtonItem *loadingIcon = [[[UIBarButtonItem alloc] initWithCustomView:spinner] autorelease]; NSArray *toolBarButtons = [[NSArray alloc] initWithObjects: fixSpace, backButton, fixSpace, fwdButton, flexSpace, loadingIcon, flexSpace, refreshButton, nil]; // toolbar toolBar = [[UIToolbar alloc] initWithFrame:CGRectMake(0, webViewHeight, contentRect.size.width, toolBarHeight)]; toolBar.autoresizingMask = UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleWidth; toolBar.items = toolBarButtons; [self.view addSubview:toolBar]; // load the request NSURL *requestString = [NSURL URLWithString:urlValue]; [webBrowserView loadRequest:[NSURLRequest requestWithURL: requestString]]; [toolBarButtons release]; } - (void)viewWillDisappear { if ([webBrowserView isLoading]) { [webBrowserView stopLoading]; webBrowserView.delegate = nil; } } #pragma mark UIWebView - (void)webViewDidStartLoad:(UIWebView*)webView { [spinner startAnimating]; } - (void)webViewDidFinishLoad:(UIWebView*)webView { [spinner stopAnimating]; } - (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType { loadUrl = [[request URL] retain]; if ([[loadUrl scheme] isEqualToString: @"mailto"]) { UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"CEDIA10" message:@"Do you want to open Mail and exit AREC10?" delegate:self cancelButtonTitle:@"No" otherButtonTitles:@"Yes",nil]; [alert show]; [alert release]; return NO; } [loadUrl release]; return YES; } - (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error { [spinner stopAnimating]; if (error.code == -1009) { // no internet connection UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"CEDIA10" message:@"You need an active Internet connection." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alert show]; [alert release]; } } #pragma mark UIAlertView - (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex { if (buttonIndex == 1) { [[UIApplication sharedApplication] openURL:loadUrl]; [loadUrl release]; } } - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc that aren't in use. [webBrowserView release]; [urlValue release]; [toolBar release]; [spinner release]; [loadUrl release]; webBrowserView = nil; webBrowserView.delegate = nil; urlValue = nil; toolBar = nil; spinner = nil; loadUrl = nil; } - (void)viewDidUnload { // Release any retained subviews of the main view. // eg self.myOutlet = nil; } - (void)dealloc { [webBrowserView release]; [urlValue release]; [toolBar release]; [spinner release]; [loadUrl release]; webBrowserView.delegate = nil; urlValue = nil; toolBar = nil; spinner = nil; loadUrl = nil; [super dealloc]; } @end 

The following is the crash log I receive:

 Date/Time: 2010-05-13 11:58:20.023 +1000 OS Version: iPhone OS 3.1.3 (7E18) Report Version: 104 Exception Type: EXC_CRASH (SIGABRT) Exception Codes: 0x00000000, 0x00000000 Crashed Thread: 0 Thread 0 Crashed: 0 libSystem.B.dylib 0x00090b2c __kill + 8 1 libSystem.B.dylib 0x00090b1a kill + 4 2 libSystem.B.dylib 0x00090b0e raise + 10 3 libSystem.B.dylib 0x000a7e34 abort + 36 4 libstdc++.6.dylib 0x00066390 __gnu_cxx::__verbose_terminate_handler() + 588 5 libobjc.A.dylib 0x00008898 _objc_terminate + 160 6 libstdc++.6.dylib 0x00063a84 __cxxabiv1::__terminate(void (*)()) + 76 7 libstdc++.6.dylib 0x00063afc std::terminate() + 16 8 libstdc++.6.dylib 0x00063c24 __cxa_throw + 100 9 libobjc.A.dylib 0x00006e54 objc_exception_throw + 104 10 CoreFoundation 0x00095bf6 -[NSObject doesNotRecognizeSelector:] + 106 11 CoreFoundation 0x0001ab12 ___forwarding___ + 474 12 CoreFoundation 0x00011838 _CF_forwarding_prep_0 + 40 13 QuartzCore 0x0000f448 CALayerCopyRenderLayer + 24 14 QuartzCore 0x0000f048 CA::Context::commit_layer(_CALayer*, unsigned int, unsigned int, void*) + 100 15 QuartzCore 0x0000ef34 CALayerCommitIfNeeded + 336 16 QuartzCore 0x0000eedc CALayerCommitIfNeeded + 248 17 QuartzCore 0x00011ee8 CA::Context::commit_root(void*, void*) + 52 18 QuartzCore 0x00011e80 x_hash_table_foreach + 64 19 QuartzCore 0x00011e2c CA::Transaction::foreach_root(void (*)(void*, void*), void*) + 40 20 QuartzCore 0x0000bb68 CA::Context::commit_transaction(CA::Transaction*) + 1068 21 QuartzCore 0x0000b46c CA::Transaction::commit() + 276 22 QuartzCore 0x000135d4 CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 84 23 CoreFoundation 0x0000f82a __CFRunLoopDoObservers + 466 24 CoreFoundation 0x00057340 CFRunLoopRunSpecific + 1812 25 CoreFoundation 0x00056c18 CFRunLoopRunInMode + 44 26 GraphicsServices 0x000041c0 GSEventRunModal + 188 27 UIKit 0x00003c28 -[UIApplication _run] + 552 28 UIKit 0x00002228 UIApplicationMain + 960 29 CEDIA10 0x00002e16 main (main.m:14) 30 CEDIA10 0x00002db8 start + 32 

Any ideas on why the app crashes?

Answer 1

I just realized what it was. In the WebViewController dealloc, I had the following:

 - (void)dealloc { [webBrowserView release]; [urlValue release]; [toolBar release]; [spinner release]; [loadUrl release]; webBrowserView.delegate = nil; urlValue = nil; toolBar = nil; spinner = nil; loadUrl = nil; [super dealloc]; 

}

So, changing it to this, it works fine and there are no leaks:

 - (void)dealloc { webBrowserView.delegate = nil; [webBrowserView stopLoading]; urlValue = nil; toolBar = nil; spinner = nil; loadUrl = nil; [webBrowserView release]; [urlValue release]; [toolBar release]; [spinner release]; [loadUrl release]; [super dealloc]; } 

This way, I did not give up the delegate before the release, so the webview should still send calls to the delegate that does not exist.

Answer 2

I would argue that this is a webView that still dispatches events to its delegate (your now dealloc'ed view handler).

Also, do you run Xcode build and analysis to find potential memory leaks / over releases?

Answer 3

The problem is that you are actually setting the webBrowserView delegate to nil AFTER you released it. By setting everything to zero, you are creating memory leaks before releasing (sending [nil release] does nothing).

Instead, it should look like

 - (void)dealloc { [webBrowserView stopLoading]; webBrowserView.delegate = nil; [webBrowserView release]; [urlValue release]; [toolBar release]; [spinner release]; [loadUrl release]; [super dealloc]; }