My issue is that the back button will not restore its visibility if my web request does not finish before or soon after ViewWillAppear has fired.
I have a navigation based iPhone 4.0 application used a simple Root and Detail view setup.
I am working with data that is returned from a webservice so when I push my detail view in its ViewDidLoad function I call my web service method in a separate thread and the Iphone lifecycle does its thing on the main thread. I must disable/hide the back button until the web request has finished (or failed) so I call self.navigationItem.hidesBackButton = YES; in ViewDidLoad and self.navigationItem.hidesBackButton = NO; in the delegate function which fires once my web request has finished or failed.
I already tried the following:
[self.navigationItem performSelectorOnMainThread:#selector(setHidesBackButton:) withObject:NO waitUntilDone:NO];
[self.navigationItem setHidesBackButton:NO];
[self.view setNeedsDisplay];
[self.navigationController.view setNeedsDisplay];
UINavigationItem *nav = self.navigationItem;
nav.hidesBackButton = NO;
Root View Controller Push Code:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
ArticleViewController *articleViewController = [[ArticleViewController alloc] initWithNibName:#"ArticleViewController" bundle:nil];
NewsArticle *newsArticle = [newsItems objectAtIndex:indexPath.row];
articleViewController.articleID = newsArticle.newsID;
[self.navigationController pushViewController:articleViewController animated:YES];
[newsArticle release];
[articleViewController release];
}
Details View Controller Code:
- (void)viewDidLoad {
[super viewDidLoad];
self.navigationItem.hidesBackButton = YES;
id scrollView = [[[self webContent] subviews] objectAtIndex:0];
if([scrollView respondsToSelector:#selector(setBackgroundColor:)] )
{
[scrollView performSelector:#selector(setBackgroundColor:)
withObject:[UIColor blackColor]];
}
[self getNewsArticle];
}
//Fires when the web request has finished
- (void) finish:(NewsArticle *)newsArticleFromSvc {
self.navigationItem.hidesBackButton = NO;
self.newsArticle = newsArticleFromSvc;
[self bindNewsArtice];
}
Any help is GREATLY appreciated I can hardly ##$&^ believe that hiding a button in a UI could cause me this much wasted time.
Try use this method of UINavigationItem :
- (void)setHidesBackButton:(BOOL)hidesBackButton animated:(BOOL)animated
I wasn't able to solve this problem. Instead I tweaked my App Logic to make hiding he back button not necessary.
Related
i have an action that allows me to present a ModalViewController and show the UITextField as a first responder, the problem is when this ModalViewController will come up it takes a little time, the cause is the keyboard, and when i grab the code to the viewDidAppear the keyboard take a little time to show up, so how can i do to make the UIViewController comes up quickly?
- (IBAction)goToModalViewController
{
ModalSearchViewController *msvc = [[ModalSearchViewController alloc] init];
self.msvc.context = context;
self.msvc.delegate = self;
[self.msvc setModalTransitionStyle:UIModalTransitionStyleCrossDissolve ];
[self presentModalViewController:msvc animated:YES];
}
The viewWillAppear of the ModalViewController:
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:YES];
[findTextField becomeFirstResponder];
}
Try like this in the viewWillAppear.
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
//[findTextField becomeFirstResponder];
[findTextField performSelector:#selector(becomeFirstResponder) withObject:nil afterDelay:0.3];
}
I know there have been a couple questions asked similar to this, but I think my issues is a little different, so bear with me.
I have a tabbed view app with table views set in 2 of the 3 tabs. I want to be able to refresh just the table view of the selected tab when the app wakes back up. I have tried using the notification center to tell my tab to refresh, but it makes the other tab crash because it is stealing the view from my progress hud. I will put some code here, so hopefully I can find a solution that will work for me.
Tab 1 ViewController
- (void)viewDidLoad {
// becomeActive just calls viewDidAppear:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(becomeActive:)
name:UIApplicationDidBecomeActiveNotification
object:nil];
[super viewDidLoad];
}
-(void)viewDidAppear:(BOOL)animated {
HUD = [[MBProgressHUD alloc] initWithView:self.view];
[self.view addSubview:HUD];
HUD.delegate = self;
HUD.labelText = #"Updating";
HUD.detailsLabelText = #"Please Wait";
[HUD showWhileExecuting:#selector(refreshData) onTarget:self withObject:nil animated:YES];
}
Tab 2 ViewController
- (void)viewDidLoad
{
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
self.navigationItem.title = [defaults valueForKey:#"companyName"];
self.view.backgroundColor = background;
tableView.backgroundColor = [UIColor clearColor];
tableView.opaque = YES;
tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
// becomeActive just calls viewDidAppear
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(becomeActive:)
name:UIApplicationDidBecomeActiveNotification
object:nil];
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
if (_refreshHeaderView == nil) {
EGORefreshTableHeaderView *view = [[EGORefreshTableHeaderView alloc] initWithFrame:CGRectMake(0.0f, 0.0f - self.tableView.bounds.size.height, self.view.frame.size.width, self.tableView.bounds.size.height)];
view.delegate = self;
[self.tableView addSubview:view];
_refreshHeaderView = view;
[view release];
}
// update the last update date
[_refreshHeaderView refreshLastUpdatedDate];
}
-(void)viewDidAppear:(BOOL)animated {
HUD = [[MBProgressHUD alloc] initWithView:self.view];
[self.view addSubview:HUD];
HUD.delegate = self;
HUD.labelText = #"Updating";
HUD.detailsLabelText = #"Please Wait";
[HUD showWhileExecuting:#selector(updateBoard) onTarget:self withObject:nil animated:YES];
// update the last update date
[_refreshHeaderView refreshLastUpdatedDate];
}
With this setup, my application will refresh tab 2 just fine, assuming that tab 2 was the last tab open before you closed the application. If I switch to tab 1 when I close, upon restarting the app, the notification calls tab 2 first and steals the view out from under my progress hud, so when I try to call the viewDidAppear method, the view is null and the app crashes. I either need to figure out how to implement the notification center better so it doesn't crash the other tab, or a better way overall to just refresh when the app becomes active. Looking forward to a good answer. Thanks in advance.
EDIT
When I run with this setup, it aborts inside the MBProgressHUD
- (id)initWithView:(UIView *)view {
// Let's check if the view is nil (this is a common error when using the windw initializer above)
if (!view) {
[NSException raise:#"MBProgressHUDViewIsNillException"
format:#"The view used in the MBProgressHUD initializer is nil."]; // <-- Aborts on this line, so they know it can happen
}
id me = [self initWithFrame:view.bounds];
// We need to take care of rotation ourselfs if we're adding the HUD to a window
if ([view isKindOfClass:[UIWindow class]]) {
[self setTransformForCurrentOrientation:NO];
}
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(deviceOrientationDidChange:)
name:UIDeviceOrientationDidChangeNotification object:nil];
return me;
}
Main problem here that notifications are received by all views, whether they will appear or not. Good practice would be to notify only those views which will appear in screen
you can use application delegate's (void)applicationWillEnterForeground:(UIApplication *)application method to handle change in application instead of notification.
if problem is all about refreshing tab that is on screen then keeping track of change in tab in AppDelegate and using that when application enters foreground would be better idea over notification.
Other option is to use viewWillAppear method in tabbarcontroller. When this method gets called, you can refresh current tab.
There really isn't much out there to help answer this question. #Learner gave me an idea that ultimately led to how I resolved this issue.
Since all of the logic I have works, the issue was to prevent the HUD from stealing the view from the other one since they both get called when they respond to the notification event. So in my -becomeActive event for both tabs, I added a check if the selectedIndex was a match for the current tab, if not, no refresh. Worked like a charm.
-(void)becomeActive:(NSNotification *)notification {
// only respond if the selected tab is our current tab
if (self.tabBarController.selectedIndex == 1) { // just set the number to your tab index
[self viewDidAppear:YES];
}
}
My iPhone app badly leaks when flipping back and forth between a main uiviewcontroller and a help uiviewcontroller .
Here is the source of the main view, followed by source of the help view.
MAIN VIEW - FLIP TO HELP.....................
// Changes from operational view to Help view.
- (IBAction)showHelp:(id)sender
{
// End trial mode:
self.stop_trial_if_started;
self.rename_trial_if_edited;
// Switch to trial help:
help_view_context = 0;
HelpView *controller = [[HelpView alloc] initWithNibName:#"HelpView" bundle:nil];
controller.delegate = self;
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:controller animated:YES];
[controller release];
}
HELP VIEW - INIT.............................
- (void)viewDidLoad {
[super viewDidLoad];
self.view.backgroundColor = [UIColor viewFlipsideBackgroundColor];
help_scroll.editable = FALSE;
return;
}
HELP - RETURN TO MAIN VIEW.........................
// User clicked the button to return to operational view:
- (IBAction)done:(id)sender {
NSLog(#"help- done");
if( help_view_context == 0 ) {
[self.delegate trial_help_DidFinish:self];
}else{
[self.delegate file_help_DidFinish:self];
}
}
MAIN VIEW - RETURN FROM HELP...............................
// Inits operational view when user changes from Help view back to operational view.
- (void)trial_help_DidFinish:(HelpView *)controller {
NSLog(#"trial_help_DidFinish");
[self dismissModalViewControllerAnimated:YES];
self.init_trial_operation;
}
You are creating a controller with ref count of 1 and a local reference each time showHelp: is called:
HelpView *controller = [[HelpView alloc] initWithNibName:#"HelpView" bundle:nil];
you are losing your reference to it at the end of this method.
You happen to have references to it in done: (self) and *_help_didFinish (controller), but you never release it in either of those locations. Dismissing the controller is fine, but you also have to release it.
(Another option would be to never create a second one, and maintain an iVar to the original.)
You could well be leaking on this line
controller.delegate = self;
What is your property declaration for the delegate. If it's anything other than assign, then you either need to change it (preferred option) or make sure you are releasing it in the dealloc method of HelpView controller.
I am implementing a simple in-app browser. In my home view (UITableViewController), I have something like:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
WebViewController *webViewController = [[WebViewController alloc] init];
switch (indexPath.row) {
case 0:
webViewController.stringURL = #"http://www.google.com";
break;
case 1:
webViewController.stringURL = #"http://www.bing.com";
break;
default:
webViewController.stringURL = #"http://stackoverflow.com";
break;
}
[self.navigationController pushViewController:webViewController animated:YES];
[webViewController release];
}
The app crashed after I repetitively navigated back and forth between my home view and webViewControllera few times.
Inside WebViewController class, I have nothing but a [UIWebView *webView] and a [UIActivityIndicatorView *activityIndicator]. Both are with attributes nonatomic, retain. Here is the implementation.
#import "WebViewController.h"
#implementation WebViewController
#synthesize webView, activityIndicator, stringURL;
- (void)dealloc
{
[self.webView release];
self.webView.delegate = nil;
[self.activityIndicator release];
[super dealloc];
}
-(void)loadView {
UIView *contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
self.view = contentView;
CGRect webFrame = [[UIScreen mainScreen] applicationFrame];
webFrame.origin.y = 0.0f;
self.webView = [[UIWebView alloc] initWithFrame:webFrame];
self.webView.backgroundColor = [UIColor blueColor];
self.webView.scalesPageToFit = YES;
self.webView.autoresizingMask = (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight);
self.webView.delegate = self;
[self.view addSubview: self.webView];
[self.webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:self.stringURL]]];
self.activityIndicator = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
self.activityIndicator.frame = CGRectMake(0.0, 0.0, 30.0, 30.0);
self.activityIndicator.center = self.view.center;
[self.view addSubview: self.activityIndicator];
}
- (void)viewDidLoad
{
[super viewDidLoad];
[self loadView];
}
- (void)webViewDidStartLoad:(UIWebView *)webView
{
// starting the load, show the activity indicator in the status bar
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
[activityIndicator startAnimating];
}
- (void)webViewDidFinishLoad:(UIWebView *)webView
{
// finished loading, hide the activity indicator in the status bar
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
[activityIndicator stopAnimating];
}
#end
I just ran my app in Instruments using the Zombies template, which shows -[UIWebView webView:didReceiveTitle:forFrame:] is the Zombie call. But I still can’t figure out what is actually the problem.
(Please download trace if needed)
Any help is greatly appreciated!
[Update]:
As #7KV7 and #David pointed out, there is an obvious bug in my dealloc function. I should call self.webView.delegate=nil; first before I release self.webView. Sorry about that. Unfortunately, after I fix it, the app still crashes in the same way.
If I delete [webViewController release]; from the first code block, the crash actually is gone. But obviously, there will be memory leak.
First of all, remove that call to loadView in viewDidLoad. The framework will the call the method when it doesn't find a view provided in XIB file. Second, your loadView is filled with memory leaks. You are allocating, initializing and retaining an object every time the method is called. So you are taking ownership twice and releasing it only once in the dealloc.
The objects are not being properly deallocated. You should do something like alloc-init-autorelease to solve this. Next thing is the that every time the controller gets loaded, because of your call to loadView, you end up creating two web view objects and two requests. You lose reference to one of them as you reassign. Herein, lies the problem mentioned in the title. You aren't able to reset the delegate of a web view object that has your controller as a delegate. Imagine a request being completed soon after you leave. Here the message will go to a zombie object. This is a pretty good example for why you need to nil out your delegates.
- (void)dealloc
{
self.webView.delegate = nil;
[self.webView release];
[self.activityIndicator release];
[super dealloc];
}
Try this dealloc. You were releasing the webview and then setting the delegate as nil. You should first set the delegate as nil and then release it. Hope this solves the issue.
I think what's happening is that you are going back while the page is still loading so the controller gets deallocated and then the webview finishes loading.
Try calling [webView stopLoading] in your viewDidUnload method to make sure this isn't happening.
Don't know if it's the cause of your problem, but this is definitely wrong:
[self.webView release];
self.webView.delegate = nil;
You cannot (safely) refer to self.webView after you release it!
Instead of pushing webViewController,add its view to self.view .
Dont call [self loadView]; in viewDidLoad.
I have a UINavigationController with two ViewControllers on the stack. At a certain point in the program execution, the second view controller is visible on the screen and at that moment, I would like to replace that ViewController with another. However, it's not working. Here is my code:
UINavigationController * thisNavController = self.waitingController;
// remove the Dummy and set the new page instead
NSMutableArray * newControllers = [NSMutableArray arrayWithArray: thisNavController.viewControllers];
[newControllers replaceObjectAtIndex: ([thisNavController.viewControllers count] - 1) withObject: page];
NSLog (#"visible before: %#", [thisNavController.visibleViewController description]);
[thisNavController setViewControllers: [NSArray arrayWithArray: newControllers] animated: YES];
NSLog (#"visible after: %#", [thisNavController.visibleViewController description]);
[thisNavController.visibleViewController.view setNeedsDisplay];
The above code produces this output:
2011-05-05 13:30:22.201 myApp[3286:207] visible before: <DummyViewController: 0x4c8b4c0>
2011-05-05 13:30:22.209 myApp[3286:207] visible after: <RealViewController: 0x60173f0>
But what is shown on the screen does not change. It seems that everything works fine after I switch tabs, so it seems that it is a redrawing problem, but setNeedsDisplay does nothing and I couldn't find a method that tells the NavigationController that its viewControllers have changed.
Is there some refresh mechanism that I have to trigger to refresh the screen?
One solution would be to say add 2 (initial) view controllers when your app is started, and only allow navigation from the 2nd and 3rd ones, falling back to the 1st (root) view controller in your senario described. You never allow navigation back to this 1st view controller or from this 1st view controller to the 2nd; you see this sort of behaviour in some of Apple's apps, like iTunes and Remote - if there's no network connect the app shows a no-network connection view immediately.
So, when you want to show the 1st view controller above, you do something like:
NSArray *array = [navigationController popToRootViewControllerAnimated:NO];
Without more info about the navigation behaviour of your app I hope this helps.
Or show a modal view controller?
The problem turned out to be the fact that I was trying to replace the view controller stack before the initial transition animation for the Dummy controller has finished. This can be prevented in the following manner.
First, preserve the (eventual) delegate, set the current object as the delegate, set a flag that animation is in progress and push the new controller:
self.oldNavigationControllerDelegate = self.waitingController.navigationController.delegate;
self.waitingController.navigationController.delegate = self;
self.isAnimating = YES;
[viewController.navigationController pushViewController: [[DummyViewController alloc] init] animated: YES];
Then, implement the UIViewControllerDelegate protocol methods as follows:
#pragma mark -
#pragma mark UINavigationControllerDelegate methods
- (void) navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
if (navigationController == self.waitingController.navigationController)
self.isAnimating = YES;
}
- (void) navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
if (navigationController == self.waitingController.navigationController) {
self.isAnimating = NO;
if (self.readyPage != nil)
[self pageIsReady: self.readyPage]; // method to load the ready controller
}
}
After that, whenever your content/controller/download/whatever is ready, make sure that the navigation controller is no longer animating. If it is, set a flag that the page is ready. If it isn't, load the page:
if (self.isAnimating)
self.readyPage = controller;
else
[self pageIsReady: controller];
And, of course, implement the actual loading of the new stack (as usual):
- (void) pageIsReady: (UIViewController *) page {
// this method should replace the dummy that is spinning there
UINavigationController * thisNavController = self.waitingController.navigationController;
// remove the Dummy and set the new page instead
NSMutableArray * newControllers = [NSMutableArray arrayWithArray: thisNavController.viewControllers];
[newControllers replaceObjectAtIndex: ([thisNavController.viewControllers count] - 1) withObject: page];
thisNavController.viewControllers = [NSArray arrayWithArray: newControllers];
thisNavController.delegate = self.oldNavigationControllerDelegate; // restore the original delegate
// clean up
self.isAnimating = NO;
self.readyPage = nil;
self.waitingController = nil;
self.oldNavigationControllerDelegate = nil;
}
This makes everybody happy :P