When I receive a memory warning in my navigation based iPhone App the background image disappears in the previously allocated navigation controllers.
The background image is set as the background property of a UIView. This view is then added to the main window of the App delegate:
UIView *backgroundView = [[UIView alloc] initWithFrame: window.frame];
backgroundView.backgroundColor = [UIColor colorWithPatternImage:[[Utilities sharedManager] getImageWithName:#"Hintergrund2"]];
backgroundView.tag = 56789;
[window addSubview:backgroundView];
[backgroundView release];
[window addSubview:[navigationController view]];
[window makeKeyAndVisible];
After I received the memory warning message and pressed the back button of the navigation controller the previous navigation controller shows up the normal Apple gray background. I have to navigate back to my home screen and navigate forward to "reset" the background image.
Can anyone tell me why the background disappears? It is not because of the image, when I set the background to a standard UIColor like blackColor the background (color) also disappears.
Thank you in advance for your help!
regards
Phil
It is undefined what the OS does with stuff added directly to the main UIWindow in case of low memory situations.
Maybe consider using a simple UIViewController for the background? You will then at least get callbacks when there is a low memory situation.
First, you should probably add your controller to the window like this:
window.rootViewController = navigationController;
I haven't tested this, but perhaps you can set the background color of the window directly:
window.backgroundColor = [UIColor colorWithPatternImage:[[Utilities sharedManager] getImageWithName:#"Hintergrund2"]];
If that doesn't work, you'll need a better way to recreate your view state in low memory situations. The most standard way to do this is by defining the background in each xib, which is reloaded. Alternatively, you could catch the low memory warning and recreate as needed by seeing if your backgroundView has a superview.
Make sure that you are setting the calling self.view.backgroundColor = [UIColor clearColor]; in the view controller's - (void) viewDidLoad otherwise the window's image will not be displayed.
- (void) viewDidLoad
{
[super viewDidLoad];
self.view.backgroundColor = [UIColor clearColor];
...
}
My problem was that I set the view's backgroundColor when it is initialized
MyTableViewController *myTVC =
[[MyTableViewController alloc] initWithStyle:UITableViewStyleGrouped];
myTVC.view.backgroundColor = [UIColor clearColor];
and not in - (void) viewDidLoad.
In this situation, the UITableViewController's view's background color was set after it was initially created. However after a low memory warning, the UIViewController's that were not displayed have - (void) viewDidUnload called on them. That deallocate their views. Just before the UIViewController was to be displayed again, - (void) viewDidLoad was called and created a new view, but the view's background color was set to the default which is not clear.
Related
I have a view being displayed modally and, before I display it, I set it's background color to transparent...
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
MyViewController_iPhone *myVC = [[MyViewController_iPhone alloc] initWithNibName:#"MyView" bundle:nil];
[myVC.view setBackgroundColor:[UIColor colorWithRed:0 green:0 blue:0 alpha:0.0]]
[[self navigationController] presentModalViewController:myVC animated:YES];
[myVC release];
}
As the view animates up onto the screen, the background is transparent, but as soon as it finishes animating upward, the view's background goes back to the original opaque white color, why?
Thanks in advance for your help!
According to this post Transparent Background with a Modal UIViewController it cannot be done. What are you trying to end up with?
This link seems to describe what you're trying to achieve. http://doganberktas.com/2010/05/18/adding-transparent-modal-view-programatically-iphone/
Is it possible with a standard UINavigationController-rooted app, to have a single ADBannerView visible at the bottom of the screen, below the view hierarchy? That is, without modifying each view-controller/view that can be pushed to the root UINavigationController, can I have a global ADBannerView be visible?
I'm not sure how to set this up, either in IB or in code. Help?
I see similar questions with vague answers. I'm looking for a concrete example.
EDIT: The better way to do this in iOS5+ is likely to use view controller containment. That is, make a root controller that contains your ad and application controller (nav, tab, etc.).
I figured out a way to do this. Here is what I did:
For my first attempt I created a new view controller called AdBannerController. For its view I created a full-screen view and two subviews. The first subview (contentView) is for regular content, the second is the AdBannerView. I used an instance of this view controller as the view controller associated with the app window ( [window addSubview: adBannerController.view] ). Then I added my UINavigationController.view as a subview of adBannerController.view: [adBannerController.contentView addSubview: navigationController.view].
This mostly worked except that viewcontrollers pushed to the UINavigationController never got their will/did-load/unload methods called. Shucks. I read in a few places that this is a symptom of the UINavigationController view not being a direct descendant of the app window.
For my second attempt I took the same AdBannerController and derived it from UINavigationController. This time, I did the following in loadView:
- (void)loadView
{
[super loadView];
_contentView = [self.view retain];
self.view = [[[UIView alloc] initWithFrame: _contentView.frame] autorelease];
[self.view addSubview: _contentView];
_adView = [[ADBannerView alloc] initWithFrame: CGRectMake(0, _contentView.bounds.size.height, 320, 50)];
_adView.currentContentSizeIdentifier = ADBannerContentSizeIdentifier320x50;
_adView.delegate = self;
[self.view addSubview: _adView];
/* for visual debugging of view layout
[[_mainView layer] setCornerRadius: 6.0];
[[_mainView layer] setMasksToBounds: YES];
[[_mainView layer] setBorderWidth: 1.5];
[[_mainView layer] setBorderColor: [[UIColor grayColor] CGColor]];
*/
}
Notice what happens - I let the superclass UINavigationController construct its regular "content" view, but I swap it out and replace it with my own view which is a container for both the content and ad views.
This works pretty well. I'm also using three20 and there were a few things required to make this work with that setup, but not too bad.
I hope this helps someone!
In Apple's dev sample code the iAdSuite project contents projects that have this done for you. Highly recommended.
In my root view controller (w/ ADBannerViewDelegate) I setup my banner by adding it to the nav controller view, which keeps it on top at all times:
banner = [[ADBannerView alloc] init];
banner.delegate = self;
banner.frame = CGRectMake(0.0, 430.0, banner.frame.size.width, banner.frame.size.height);
[self.navigationController.view addSubview:banner];
Note you will have to comment out layoutAnimated in delegate method bannerViewDidLoadAd as it will try to move the ad view up:
- (void)bannerViewDidLoadAd:(ADBannerView *)banner
{
//[self layoutAnimated:YES];
}
I adapted the approach suggested in the iAdSuite given here
http://developer.apple.com/library/ios/#samplecode/iAdSuite/Introduction/Intro.html
I downloaded the code and focused on the 'tab' example. I copied over the BannerViewController.h/.m as is into my project.
I created all my views in the usual way with the storyboard approach. However, in my AppDelegate class I then accessed the already built tab bar - containing all the storyboard built viewControllers.
The AppDelegate class implements the TabBarControllerDelegate protocol:
#interfaceAppDelegate : UIResponder <UITabBarControllerDelegate, UIApplicationDelegate>
The AppDelegate implementation didFinishLaunchingWithOptions method grabs the pre-built tabBar, setting its delegate to self (e.g. the AppDelegate class).
-(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:
// ----------------------------------------------------------
// Set the TabBarController delegate to be 'self'
// ----------------------------------------------------------
_tabBarController = (UITabBarController*)self.window.rootViewController;
// tabController.selectedIndex = [defaults integerForKey:kOptionLastTabSelectedKey];
_tabBarController.delegate = self;
// update tab bar per iAdSuite approach
[self updateiAd];
I then built a new set of controllers per the iAdSuite approach and reset the tab bar with these new tab bar items.
-(void)updateiAd {
NSArray* viewControllers = [_tabBarController viewControllers];
NSMutableArray*newViewControllers = [[NSMutableArray alloc] init];
BannerViewController*bvc=NULL;
for(UIViewController * vc in viewControllers) {
bvc = [[BannerViewController alloc] initWithContentViewController:vc];
[newViewControllers addObject:bvc];
}
// set the new view controllers, replacing the original set
[_tabBarController setViewControllers:newViewControllers];
}
This approach puts the same 'ad' at the bottom of each view, exactly as needed. I also had to set the view title in the viewDidLoad method of each custom viewController (somehow, setting it on the bar item didn't seem to work not did setting the image; the later may reflect an issue with my images however).
My original configuration was
TabViewController
NavController1 NavController2 NavController3 ...
| | |
CustomViewController1 CustomViewController2 CustomViewController3
My final configuration is now
TabViewController
NavController1 NavController2 NavController3 ...
| | |
iAdView1 iAdView2 iAdView3
| | |
CustomViewController1 CustomViewController2 CustomViewController3
In terms of view lifecycle, I should add that only the NavControllers are in existence at the time the updateiAd method is called.
The individual CustomViewControllers1/2/3/etc get created after the call completes.
The docs say that the whole subview hierarchy can be created in -loadView. But there's also this -viewDidLoad method which sounds nice to ovewrite for actually building the hierarchy, when the view loaded. I guess it's a matter of taste only. But maybe doing so in -viewDidLoad hast the advantage that the view controller already adjusted the frame of the view correctly to accomodate for the status bar or any other kind of bar like tab bar or tool bar?
viewDidLoad is called after the view hierarchy is built. loadView is supposed to build the hierarchy and set the view property if you are not loading from a NIB file.
viewDidLoad is also called after a memory warning if you're view got unloaded. When you get a memory warning viewDidUnload is called to give you a change to release objects that can be easily recreated in viewDidLoad.
Read the "Subclassing Notes" and "Memory Management" sections of the class description to better understand how it works.
I think the logic behind it is that in loadView you build elements, i.e. instantiate and allocate memory, this being the most costly action. So when [super loadView] has been called all the way up the ladder, all views are ready to be displayed and the expensive part is over.
In - (void) viewDidLoad you populate the views with data, viewDidLoad "know" all elements are ready to have text set on them, values, content etc.
UINavigationControllers etc. can benefit from knowing when everything is ready as to start animating view on to the screen. If you place all the instantiation/allocation in the viewDidLoad you force the controller to do everything, including being animated on screen, at the last moment. I don't know the exact details, but this is what I get from the documentation and the "life-cycle" of the UIViewController
I usually do it like this:
- (void)loadView {
[super loadView];
UIView *container = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 20.0f, 320.0f, 460.0f)];
UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"bg02.png"]];
[container addSubview:imageView];
[imageView release];
UIImageView *background = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"bg_search.png"]];
[container addSubview:background];
[background release];
UILabel *textlabel = [[UILabel alloc] initWithFrame:CGRectMake(10.0f, 10.0f, 200.0f, 20.0f)];
[self setLabel:textlabel];
[container addSubview:self.label];
[textlabel release];
[self setView:container];
[container release];
}
- (void)viewDidLoad {
[self.label setText:#"I am ready!"];
[super viewDidLoad];
}
I sometimes use the viewWillAppear to set data, if it is a view controller that sports modalViewControllers or pushes a new viewController where a user sets data that needs to be updated on the parent when popping the view again (e.g. a UITableViewController with a list of songs is pushed, the user selects a song and the controllers pops and the parent now displays the song title the user selected etc.) Any case wher the view goes on/off screen often, but needs to display newly changed data.
I have a core data application which uses a navigation controller to drill down to a detail view and then if you edit one of the rows of data in the detail view you get taken to an Edit View for the that single line, like in Apples CoreDataBooks example (except CoreDataBooks only uses a UITextField on its own, not one which is a subview of UITableViewCell like mine)!
The edit view is a UITableviewController which creates its table with a single section single row and a UITextfield in the cell, programatically.
What I want to happen is when you select a row to edit and the edit view is pushed onto the nav stack and the edit view is animated moving across the screen, I want the textfield to be selected as firstResponder so that the keyboard is already showing as the view moves across the screen to take position. Like in the Contacts app or in the CoreDataBooks App.
I currently have the following code in my app which causes the view to load and then you see the keyboard appear (which isn't what I want, I want the keyboard to already be there)
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
[theTextField becomeFirstResponder];
}
You can't put this in -viewWillAppear as the textfield hasn't been created yet so theTextField is nil. In the CoreDataBooks App where they achieve what i want they load their view from a nib so they use the same code but in -viewWillAppear as the textfield has already been created!
Is there anyway of getting around this without creating a nib, I want to keep the implementation programatic to enable greater flexibility.
Many Thanks
After speaking with the Apple Dev Support Team, I have an answer!
What you need to do is to create an offscreen UITextField in -(void)loadView; and then set it as first responder then on the viewDidLoad method you can set the UITextField in the UITableViewCell to be first responder. Heres some example code (remember I'm doing this in a UITableViewController so I am creating the tableview as well!
- (void)loadView
{
[super loadView];
//Set the view up.
UIView *theView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
self.view = theView;
[theView release];
//Create an negatively sized or offscreen textfield
UITextField *hiddenField = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, -10, -10)];
hiddenTextField = hiddenField;
[self.view addSubview:hiddenTextField];
[hiddenField release];
//Create the tableview
UITableView *theTableView = [[UITableView alloc] initWithFrame:[[UIScreen mainScreen] bounds] style:UITableViewStyleGrouped];
theTableView.delegate = self;
theTableView.dataSource = self;
[self.view addSubview:theTableView];
[theTableView release];
//Set the hiddenTextField to become first responder
[hiddenTextField becomeFirstResponder];
//Background for a grouped tableview
self.view.backgroundColor = [UIColor groupTableViewBackgroundColor];
}
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
//Now the the UITableViewCells UITextField has loaded you can set that as first responder
[theTextField becomeFirstResponder];
}
I hope this helps anyone stuck in the same position as me!
If anyone else can see a better way to do this please say.
Try do it in viewDidAppear method, works for me.
I think the obvious solution is to create the textfield in the init method of the view controller. That is usually where you configure the view because a view controller does require a populated view property.
Then you can set the textfield as first responder in viewWillAppear and the keyboard should be visible as the view slides in.
have you tried using the uinavigationcontroller delegate methods?:
navigationController:willShowViewController:animated:
How can I make it so when a tab is selected, the current one is unloaded, and the next one is loaded so only one loaded at a time? Or should I not even do this? I know how to do it with a normal UIViewController as the root VC, but not sure with a UITabBarController. Also, is there a way to animate the transition from one tab to the next? Any help? Thanks!!
EDIT: ... If I unload the view controllers, then their icons on the tab bar are gone... maybe I'll just unload their views..
I can answer both questions in one...
You just need a class that acts as the UITabBarController delegate, then implement a method like so:
// Animate tab selections so they fade in and fade out
-(void)tabBarController:(UITabBarController*)tbc didSelectViewController:(UIViewController*)newSelection
{
[UIView beginAnimations:#"TabFadeIn" context:nil];
[UIView setAnimationDuration:0.6];
for( UIViewController* vc in tbc.viewControllers )
vc.view.alpha = (vc==newSelection) ? 1 : 0;
[UIView commitAnimations];
}
Now my code simply makes the tab bars fade in and out, but you could also do work here to unload non-used tabs. Sometimes that is a good idea if some of the tabs will be using a ton of memory.
You cant really manage the UITabBarController unfortunaly so you cant do lazy loading. You can by managining your own TabBar but you said u knew that already,
to manage your own tab bar though all you gotta do is setup a UITabBar with its TabBarItems in a ViewController, then implement the TabBar Delegate protocol, mainly the – tabBar:didSelectItem: method which is called whenever the tabbarItem selection is changed, then based on the item id you can load your new ViewController and release any others
so: Edit: this code goes in your UIViewController
-(void)addTabBar{
NSMutableArray* items=[[NSMutableArray alloc] init];
UITabBarItem *eventsItem= [[UITabBarItem alloc] initWithTitle:#"Events" image:nil tag:0];
UITabBarItem *albumItems=[[UITabBarItem alloc] initWithTitle:#"Album" image:nil tag:1]; //the tag is how you tell what was clicked
[items addObject:homeItem];
[items addObject:albumItems];
//MyTabBar is of type UITabBar
myTabBar=[[UITabBar alloc] initWithFrame:CGRectMake(0,411,320,49)];
[myTabBar setItems:items];
myTabBar.delegate=self; //you gotta implement the UITabBar delegate protocol
[myTabBar setSelectedItem:eventItem]; //set the selected item
[homeItem release];
[eventsItem release];
[albumItems release];
[items release];
[self.view addSubview:myTabBar]
}
then the protocol method would look something like below
- (void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item
{
if(item.tag == 0 )
{
//load the ViewController that pertains to this item and release others
}
...etc
}
Lazy loading is not an UITabBarController task. Instead, it is responsability of your viewControllers associated with your Tab.
To release the UIView, associated with each UIViewControllers, every time you change the TabBarItem, you must implement the following method in each UIViewController subclass, associated with your UITabBarController.viewControllers property:
-(void)viewDidDisappear {
[self.view removeFromSuperview];
self.view = nil;
}
Obviously, this will remove the self.view associated with your UIViewController. However, if your code is smart enough, this will remove all the related objects.
For example, suppose that your loadView method is as follow:
-(void)loadView {
UIView *contentVew = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
self.view = contentView;
…
...
UILabel *aLabel = [[UILabel alloc] initWithFrame:CGRectMake(0,0,320,50)];
…
…
[contentView addSubview:aLabel];
[aLabel release];
…
[contentView release];
}
This means that every object inside the contentView and their memory responsabilities are demanded to the contentView, that is released and attached to the self.view property.
In this scenario, removing the self.view (that's the reference to the contentView) resulting in a domino-style releasing of every object, that's your goal.
Best regards
Not sure why you'd want to do this, the current tab will get unloaded anyway if there's a memory issue involved. That's what -viewWillAppear, -viewDidUnload, etc. are for.
UITabBarController does lazy load all of its view controllers. When a tab is switched out, then it's view is subject to being deallocated in a memory tight situation. It is then recreated when it is chosen the second time. Furthermore, most of your memory hits are in your views and not the view controllers. Hence, don't worry about the memory hit from the view controller. The view is the proze.
If you are running on v3 of the OS, then you can use the -viewDidUnload method to ensure the maximal amount of memory reduction.
Andrew
I'm currently using this to unload inactive view controllers in the tab bar (based on Kendall's answer)
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController: (UIViewController *)viewController {
// reload all inactive view controllers in the tab bar
for (UIViewController *vc in tabBarController.viewControllers) {
if(vc != viewController)
[vc didReceiveMemoryWarning];
}
}