I have a UIButton in my app that when pressed it shows the next view controller. Sometimes the UI locks up and the app freezes for a moment due to background processes. When this happens the user might tap the button multiple times because nothing happened immediately on the first tap, and when this occurs the UINavigationController pushes the ViewController again a bunch of times on top of itself, so that you have to go back several times to get back to home. Here is my code:
- (void)viewDidLoad {
[super viewDidLoad];
self.pushVCButton.multipleTouchEnabled = NO;
}
- (IBAction)pushVCButtonPressed:(id)sender {
self.pushVCButton.enabled = NO;
ViewController *viewController = [[ViewController alloc] init];
[self.navigationController pushViewController:viewController animated:YES];
self.pushVCButton.enabled = YES;
}
How do I get this to never push multiple instances of viewController?
You should really try to make the background process run not on UI thread, but if you can not try setting the button enabled to yes only when view did disappear or listen for completion of push animation:
- (IBAction)pushVCButtonPressed:(id)sender {
self.pushVCButton.enabled = NO;
ViewController *viewController = [[ViewController alloc] init];
[self.navigationController pushViewController:viewController animated:YES];
// Hack: wait for this view to disappear to enable the button
//self.pushVCButton.enabled = YES;
}
- (void)viewDidDisappear:(BOOL)animated {
[super viewDidDisappear:animated]
self.pushVCButton.enabled = YES;
}
Also make sure that the action is not called twice.
Related
in my app i am trying to make a slider using the LWSlideShow LWSlideShow
the source of images are fetched from my server after trying the solution here i stuck with error that said unbalanced call and it means that i am presenting a modal view on a view that did not completed his animation after solving this problem by putting animation to no the splashView that i present will be dismissed before the images are downloaded here is my code for further explanation:
- (IBAction)goDownload {
UIViewController *vc = [self.storyboard instantiateViewControllerWithIdentifier:#"Splash"];
[self.navigationController presentViewController:vc animated:YES completion:nil];
dispatch_async(dispatch_get_main_queue(), ^{
NSMutableArray *array = [#[] mutableCopy];
LWSlideItem *item = [LWSlideItem itemWithCaption:#""
imageUrl:#"http://code-bee.net/geeks/images/cover-1.jpg"];
[array addObject:item];
item = [LWSlideItem itemWithCaption:#""
imageUrl:#"http://code-bee.net/geeks/images/cover-2.jpg"];
[array addObject:item];
item = [LWSlideItem itemWithCaption:#""
imageUrl:#"http://code-bee.net/geeks/images/cover-3.jpg"];
[array addObject:item];
LWSlideShow *slideShow = [[LWSlideShow alloc] initWithFrame:CGRectMake(0, 0, CGRectGetWidth(self.view.bounds), 120)];
slideShow.autoresizingMask = UIViewAutoresizingFlexibleWidth;
//slideShow.delegate = self;
[self.view addSubview:slideShow];
slideShow.slideItems = array;
if ([slideShow.slideItems count] == [array count]) {
[self dismissViewControllerAnimated:YES completion:nil];
}
});
}
//
//-(void)viewWillAppear:(BOOL)animated
//{
//
// UIViewController *vc = [self.storyboard instantiateViewControllerWithIdentifier:#"Splash"];
// [self.navigationController presentViewController:vc animated:YES completion:nil];
//}
- (void)viewDidLoad {
[super viewDidLoad];
[self goDownload];
}
also you can see from the code that also i try to use viewWillAppear same thing happened what i want is when the images are downloaded the splashView need to be dismissed i dont know what i am doing wrong
Running that code from a VC anytime before viewDidAppear (like viewDidLoad, viewWillAppear) will cause the problem you describe. But you probably don't want the slide show view to appear - even for an instant - until you're done fetching the assets. This is a common problem.
The solution is to realize that the "splash screen" and the network tasks aren't just preamble, they are as much a part of your application as the slide show.
EDIT
Make that Splash vc the app's initial view controller in storyboard. Right now, the slide show vc probably looks like this:
Uncheck the "Is Initial View Controller" checkbox, find your splash view controller (in the same storyboard, I hope) and check it's box to be the initial view controller. Now your app will start up on the splash vc, like you want it.
When the splash vc done, it can present the slide show vc, or it can even replace itself (with the slide show ) as the app window's root.
To replace the UI, I use variations of this snippet...
// in the splash vc, after all of the asset loading is complete
// give what used to be your initial view controller a storyboard id
// like #"MySlideShowUI"
UIViewController *vc = [self.storyboard instantiateViewControllerWithIdentifier:#"MySlideShowUI"];
UIWindow *window = [UIApplication sharedApplication].delegate.window;
window.rootViewController = vc;
[UIView transitionWithView:window
duration:0.3
options:UIViewAnimationOptionTransitionCrossDissolve
animations:nil
completion:nil];
I have a trio of functions and a property that I use to control my popovers as follows:
-(void)dismissPopoverIfPresentAnimated:(BOOL)animated
{
if (self.currentPopover)
{
[self.currentPopover dismissPopoverAnimated:animated];
self.currentPopover = nil;
}
}
-(void)presentViewController:(UIViewController *)viewController inView:(UIView *)view fromRect:(CGRect)rect suppressArrow:(BOOL)suppressArrow
{
//Did the user just tap on a button to bring up the same controller that's already displayed?
//If so, just dismiss the current controller.
BOOL closeOnly = NO;
if (self.currentPopover)
{
UIViewController *currentController = [self.currentPopover.contentViewController isKindOfClass:UINavigationController.class] ? ((UINavigationController *)self.currentPopover.contentViewController).topViewController : self.currentPopover.contentViewController;
UIViewController *newController = [viewController isKindOfClass:UINavigationController.class] ? ((UINavigationController *)viewController).topViewController : viewController;
if ([currentController isKindOfClass:newController.class])
closeOnly = YES;
[self dismissPopoverIfPresentAnimated:NO];
}
if (!closeOnly)
{
self.currentPopover = [[UIPopoverController alloc] initWithContentViewController:viewController];
self.currentPopover.backgroundColor = [UIColor whiteColor];
[self.currentPopover presentPopoverFromRect:rect inView:view permittedArrowDirections:(suppressArrow ? 0 : UIPopoverArrowDirectionAny) animated:YES];
}
}
(instancetype) initWithContentViewController:(UIViewController )viewController
{
self = [super initWithContentViewController:[[UIViewController alloc] init]];
if (self)
{
UIViewController contentViewController = super.contentViewController;
[contentViewController addChildViewController:viewController];
[viewController didMoveToParentViewController:contentViewController];
[contentViewController.view addSubview:viewController.view];
[self setPopoverContentSize:viewController.preferredContentSize animated:NO];
}
return self;
}
This runs fine in iOS 7, but in iOS 8 the problem is there is a delay between the call to presentPopoverFromRect and when the item actually shows up onscreen. So, if a user double taps a button to show a popover, the first tap will properly dismiss, then "start" the showing of the new controller. The second tap will make the dismiss call (the popover is not yet visible) and then not show the new controller (this is a design feature so that click a button will show a popover, clicking it again will hide it).
The problem is that the call to dismiss the popover doesn't actually work and the popover will show up. At that point I can't get rid of it because my property is nil and I think it is not showing.
My guess is this is an iOS 8 bug where the dismiss somehow doesn't see a visible popover and thus doesn't do anything, where instead, it should prevent it from showing up.
Oh, one last note is that the call to presentViewController is always done on the main thread.
The problem I am experiencing is that when i try to pop a view controller using the default back swipeGesture in iOS7 viewDidDisappear of the present ViewController does not always get called after viewWillDisappear. I am using the UINavigationController as rootViewController.
App remain struck and does not receive any user inputs after this scenario. Sometimes app gets crashed, when i look at the log: it shows "Can't add self as subview' and in crash log, it showss EXC_BAD_ACCESS. How to fix this, but when i use back button in navigation bar app works normally.
- (void)viewWillDisappear:(BOOL)animated
{
// [self.navigationController.navigationBar setAlpha:1.0f];
[self createBarButtonITems];
self.navigationItem.title = #"Back";
}
- (void)viewDidDisappear:(BOOL)animated
{
[self zoomOutTableWithoutAnimation];
}
-(void)zoomOutTableWithoutAnimation
{
backgroundView.frame = CGRectMake(0,0,320,480);
backgroundView.transform=CGAffineTransformMakeScale(1, 1);
sideMenuTableView.transform=CGAffineTransformMakeScale(0.5,0.5);
sideMenuTableView.frame = CGRectMake(0,150,self.view.frame.size.width/2, self.view.frame.size.height);
sideMenuTableView.hidden = YES;
}
As you mentioned swipe back gesture, this is probably due to the interactive pop back.
As it is mentioned in WWDC 2013, session Custom Transitions Using View Controllers, you cannot assume a viewWillDisappear will be followed by viewDidDisappear. The same goes to viewWillAppear and viewDidAppear.
I'm not sure why you want to call
[self createBarButtonITems]
in viewWillDisappear, did you mean viewWillAppear?
Anyway, it seems to me that [self createBarButtonITems] did some side effect.
Try the following code in viewWillDisappear to undo the side effect:
- (void)viewWillDisappear
{
[self doSomethingHasSideEffect];
id <UIViewControllerTransitionCoordinator> coordinator;
coordinator = [self transitionCoordinator];
if(coordinator && [coordinator initiallyInteractive])
{
[coordinator notifyWhenInteractionEndsUsingBlock:
^(id <UIViewControllerTransitionCoordinatorContext> ctx)
{
if(ctx.isCancelled)
{
[self undoAnySideEffect]
}
}];
}
}
From your code what I can understand is you need a back button with title #"Back" instead of the previous view controllers title
just add this code tho your view controller, in which you trying to do the above stuff view did load method
UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithTitle:(IS_IOS_7 ? #"" : #"Back") style:UIBarButtonItemStylePlain target:Nil action:nil];
self..navigationItem.backBarButtonItem = backButton;
Add [super viewWillDisappear:animated];
- (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
[self createBarButtonITems];
self.navigationItem.title = #"Back";
}
Is is possible to have a UIView preloaded so that it will load faster when the user taps on button to load it? Currently I've got a library of informaiton that I'm attempting to load when the user taps a button, and for now it seems to be "ok" , but it makes the navigation to the page choppy, because of all the information in the library it's loading.
Thanks in advance!
It should be possible to split the setup of a View Controller from code that displays the view after a button is pushed. This will eliminate the lag when the button but the task to setup the view controller still need to be done sometime during execution (You can for example put it in the ViewdidAppear method so it is executed while waiting for the button to be pushed.
Take this code for example:
-(IBAction) button_pushed {
/*setup */
NewVC *vc = [[NewVC alloc] init];
vc.var1 = var1;
vc.var2 = x;
[vc setup];
/*display */
[self.navigationController pushViewController:vc animated:NO];
return;
}
You can split the code that setup the view from the code that displays the view
into :
#synthesize vc;
…..
- (NewVC) setup {
//setup
NewVC *vc1 = [[NewVC alloc] init];
vc.var1 = var1;
vc.var2 = x;
[vc setup];
return(vc1);
}
-(void) ViewDidAppear {
if (setupready) {
vc = [self setup];}
return;
}
-(IBAction) button_pushed:(ID) sender {
//display
[self.navigationController pushViewController:vc animated:NO];
return;
}
I'm confused. I have a navigation controller with a BarItem which opens a first view. After some work is done, I want this view to disappear and I want a second view to open.
root view: navigation controller
first view: activity indicator, where some data is put together
second view: MFMailComposeViewController
In the root view, the BarItem runs these lines to open the first view:
IndicatorViewController *indicator = [[IndicatorViewController alloc] initWithNibName:#"IndicatorViewController" bundle:nil];
indicator.view.backgroundColor = [UIColor clearColor];
self.modalPresentationStyle = UIModalPresentationCurrentContext;
[self presentModalViewController:indicator animated:YES];
The first view (IndicatorViewController) does some work and finally runs
[self dismissModalViewControllerAnimated:YES];
This works fine. But - how do I open the second view?
I tried this:
I open the second view. After closing the second view, my first view pops up again (since it is still there) and get's dismissed at this point. This code is placed in the first view:
- (void) viewDidAppear:(BOOL)animated {
static BOOL firstTime = YES;
if (firstTime) {
//do stuff that takes some time (that's why I show the indicator)
MailViewController *controller = [[MailViewController alloc] init];
if (controller)
[self presentModalViewController:controller animated:YES];
firstTime = NO;
} else {
[self dismissModalViewControllerAnimated:YES];
}
}
Since the first view pops up again, the user can see the indicator one more time, after the second view is closed - and that is not what I want.
What am I missing here? What would be the better way to do this?
I would do something like this. Make a navigationController, and make the first view as the root controller. Then do something like this:
FirstView.m
- (void)viewDidLoad
{
[super viewDidLoad];
[self.navigationController setNavigationBarHidden:YES];
}
- (void) nextView { // however you get to your next view, button/action/etc.
UIViewController *screen = [self.storyboard instantiateViewControllerWithIdentifier:#"yourIdentifier"];
[self.navigationController pushViewController:screen animated:YES];
}
Then in the second view:
SecondView.m
- (void) nextView { // however you get to your next view, button/action/etc.
UIViewController *screen = [self.storyboard instantiateViewControllerWithIdentifier:#"yourIdentifier"];
[self.navigationController pushViewController:screen animated:YES];
}
And finally in the rootview:
RootView.m
- (void)viewDidLoad
{
[super viewDidLoad];
NSArray *navStack = [NSArray arrayWithObject:self];
self.navigationController.viewControllers = navStack;
[self.navigationController setNavigationBarHidden:NO];
}
This will make your RootView the new rootview of the NavigationController.
self.navigationController.viewControllers
is the array with all the ViewControllers that are on the navcontrollers stack. The first object is the rootcontroller. If we replace the whole array with our own array, it knows only one item. You CAN go back by dismissing if that's what you want though. This isn't the prettiest way of doing it, but it's not the worst either.