I'm trying to get the following functionality in my iPhone app:
When backgrounded, stays running (doesn't have to do any background work)
When resumed, app picks up where it was left off
I'm mainly wanting the same screen on my app still up, as there are several UINavigationControllers within a UITabBarController.
I have done all of the following:
Made sure I'm compiling with 4.1 SDK
Set UIApplicationExitsOnSuspend to false
Handle DidEnterBackground and WillEnterForeground in my AppDelegate
Call BeginBackgroundTask in DidEnterBackground, to attempt to keep my app open
I'm using MonoTouch, but that it probably beside the point. I can take answers in Obj-C, for sure.
I've tested my app on a jailbroken phone with Backgrounder, and I see the "app in background" badge disappear immediately after pushing the home button. I also tried setting UIBackgroundModes in my Info.plist, but to no avail.
Is there anything I'm missing?
Or is this something I would have to implement on my own to resume the previous state of my app? Everywhere I've read talks like it should just work automatically.
If you don't want to be doing work in background, don't call beginBackgroundTask. That call is for situations where you want to do some kind of work in the background. And if you don't finish that work fast enough, iOS will terminate your app.
When I upgraded to iOS 4.x, my MT application started exhibiting this behavior without me having to do anything. iOS should take care of it for you.
I finally got in touch with someone on MonoTouch's irc.
In MonoDevelop there is an option to make a dual iPad/iPhone project, which I used. This is causing my app to behave as if it's running with the 3.2 SDK when deployed to the device.
I think my solution is to install the iOS 4.2 SDK that just came out, since this ads the new multi-tasking feature on iPad.
Not only do you need to support going into the background, you also need to support cases where your app has been terminated. In your app’s initialization code, you should resume the state that it was in. For instance, when you push a view controller, use NSUserDefaults to store a value for the currently-displayed screen, and then when you start read that value and display the associated screen.
Related
I am developing an app for iPhone.
I am looking for a way to run some code once a drag gesture is recognized on the homescreen (or on all screens if possible).
Does anyone know how to get this with the iOS SDK using Xcode and Objective-C?
Your app cannot receive gestures anywhere in iOS except within itself and its own views while it's active (not counting system notifications and the app icon).
I doubt this is possible. To do this, you will need to hook into the OS at a lower level than is usually allowed.
iOS is locked down much more than Mac OS, I'm afraid.
So I made an app, And it runs on all possible platforms except the ipad device. I would understand if it ran on the ipad device and not the iphone device since the processor is better on the ipad, but this has me stumped. It also worked fine on the ipad simulator. Can anyone think of a reason why this could be?
There are too few details to give an explanation. A possibility is: when you run the app in two different devices, iPhone and iPad, some nib files could be different. Even the app delegate is different if you use XCode templates for universal apps. So this means that it is possible that the code executed is different in the two devices.
So imagine that in the iPad app delegate / view controller you're allocating - at launch - a lot of memory (scroll view with many large images for example). Then the app will not crash in the simulator (it uses your Mac memory). The app will not crash in the iPhone (different code). So at the end it will crash in the iPad only.
Other possibilities: you're going short in memory very soon. But the iPad 1 has less memory than iPhone 4G.
Other possibility: the watchdog timer kills your app at launch. It happens on the iPad 1 only because you're loading a few large images and it takes a lot of time, just enough to be killed by the watchdog.
Other possibility: iPad 1 is still with iOS 3.2, while iPhone and simulator are linked to iOS 4.0. In this case it is easy to have the app crashing in iPad 1 by calling one of the many new APIs introduced with iOS 4.
As you can see there are many possible explanations...
add target for device or convert it to universal application
Yes, it's easy to target both platforms. If you login to ADC and read the Programming Guide, it'll provide the basics for specific development. I can't legally speak of the "how."
Um. If you follow their directions, build two targets, share your source within the same project... then you'll be set. It's the same SDK, just different Nibs & main(), from what I can tell.
You say different xibs... you might be missing an Outlet connection somewhere.
Ok gents, sorry but I did not provide enough information for any of you to correctly answer this, but! here was my problem.
I had a login screen with 2 textfields, and a submit button. The submit button would release the current view and add a new view. I would usually press submit while the keyboard is being shown. Aparantly this makes everything blow up. You must manually hide the keyboard first. Hopefully this saves somebody some time.
I have tabbar-based application. When I put in my plist UIBackgroundModes (my application is supposed to support voip), the GUI doesn't load. It sucks on Splash screen and doesn't load the first tab view. When i remove the UIBackgroundModes property from info.plist, it works fine. More than that, pressing the home button when it stuck does nothing. Did somebody encountered a similar problem? (The problem exists on simulator)
Thanks,
Nava
It appears, that the problem happens on Simulator only, it works on the device... So the solution (temporary one) is not to put UIBackgroundModes into info.plist for simulator version.
You are responsible for loading/unloading the interface when going in and out of the background mode. You'll also need to update the interface accordingly when coming out of background.
iOS helps a bit by taking a screenshot before putting the app in background and displaying it when getting the app to foreground (a bit like Default.png when starting the app) and also some UIImage caching.
It might be worth sharing some code.
Supporting Background State Transitions
Supporting the background state transition is part of the fundamental architecture for applications in iOS 4 and later. Although technically the only thing you have to do to support this capability is link against iOS 4 and later, properly supporting it requires some additional work. Specifically, your application delegate should implement the following methods and implement appropriate behaviors in each of them:
application:didFinishLaunchingWithOptions:
applicationDidBecomeActive:
applicationWillResignActive:
applicationDidEnterBackground:
applicationWillEnterForeground:
applicationWillTerminate:
Being a Responsible, Multitasking-Aware Application
Applications that run in the background are more limited in what they can do than a foreground application. And even if your application does not run in the background, there are are certain guidelines you should follow when implementing your application.
Do not make any OpenGL ES calls from your code. You must not create an EAGLContext object or issue any OpenGL ES drawing commands of any kind. Using these calls will cause your application to be terminated immediately.
[...]
iOS Application Programming Guide
I see this bug as well. It's very annoying. It's as if the app is stuck in the simulator and won't keep going. When this happens, I know how to "unstick" it.
In the simulator I just go to menu Hardware > Lock and then unlock the phone again. Now I stop the debugger and start the app again. This seems to kick it back to life.
Fortunately this bug doesn't happen on a real phone, only in the simulator.
I have upgraded my iPhone SDK from 3.1.2 to 4. The application which I developed in previous version is running fine but I have only one problem.
When I close the application it is not calling application termination and deallocating anything. When I click home button application quits but when I open it again it opens exactly where I left it.
Does anyone else had this issue if yes how did you solve that?
Thanks
What you are seeing is the state-saving multitasking that all sdk4 apps do. It isn't calling those methods because you app is not terminating, iOS is just saving the state and pushing it to the background. If you notice, the debugger doesn't unhook when you hit the home button now either. If you look into the new sdk documentation, there are methods when you app enters the background, which sound like the place you want to move the code that was in your 'willTerminate' method.
Edit: Here is the documentation for those methods
applicationDidEnterBackground:
applicationWillResignActive:
At a guess, I'd say that your application is not terminating, but is staying present in the background. It will be terminated when memory becomes scarce in the same way as it would be terminated in the 3.x days.
Example: My Default.png image shows the start screen of my app with an empty interface. When the app is launched from scratch the first time, this is cool. It appears like it started quickly. But when the user quits it and the app just goes to background, and then the user opens it, this sucks. Then I always end up with a wrong "snapshot" as launch image and my app then looks completely different after launch because it is like it was left the last time.
I would have to disable the Default.png when my app just goes to background, or I would have to enable it when it gets really terminated. Any way to do this?
It sounds to me like your app isn't being suspended. Every app that I've used that supports fast-app switching hasn't shown its default png when I open it after suspending it.
Are you sure your app is supporting fast-app switching and that it is being suspended?
Just updating my answer for some clarity that was revealed in the comments:
In order to take advantage of fast-app switching, the following conditions need to be met:
App needs to be compiled against the 4.0 SDK
App needs to be running on a multitasking-capable device such as:
iPhone 4
iPhone 3GS
iPod touch 3rd Generation
info.plist must not contain the UIApplicationExitsOnSuspend key.