When I pressing "home" button, app calling - (void)applicationWillResignActive:(UIApplication *)application, ok its good, but when I wait for a some time (10-15 mins), app starting from first loading screen, why? I have added:
[UIApplication sharedApplication].idleTimerDisabled = YES;
But not success. I think it goes to suspended mode, how do I prevent this? Thanks.
It means that your app has been killed by the system.
You can't prevent it completely, the system kills background apps when it needs more memory, but you can do something like this:
free as memory as you can when the app goes in background: doing this, when the system needs memory, your app won't be one of the first to be killed because its footprint is low.
Since you can't be sure that your app won't be killed, use state preservation / restoration: Link
EDIT:
since your app needs to reproduce audio in the background (as written in the comments) I give you some extra advices.
remember to register your app background mode (from this link: Multitasking guide) --> "by including the UIBackgroundModes key (with the value audio) in its Info.plist file"
the app continues to work in the background since it's playing audio, but when the audio is suspended the app is suspended too (it means that it can be killed). So, you must use state preservation to restore it when the user comes back.
Another extract:
"When the UIBackgroundModes key contains the audio value, the system’s media frameworks automatically prevent the corresponding app from being suspended when it moves to the background. As long as it is playing audio or video content, the app continues to run in the background. However, if the app stops playing the audio or video, the system suspends it."
You app has exited. If you want it to come back to where you left off you'll have to preserve the state somehow, check on launch, and then restore the state.
Related
we can easily capture a view(screenshot) programmatically in iPhone.
But i am trying to capture screen automatically after every 5 seconds.that also, can be done.
But my main objective is , to capture screen, even if the app is closed, i.e in background.
Apple doesn't allow to background process to run for a long time, but can we do it for 5-10 min in background.
Capturing screen,even if the app is closed.Ofcourse user can close this function, within the app.
Apple might reject this, but is this possible ?
Regards
This is possible but it's not easy. You can register you app (via a .plist setting) as being a media app, this will allow it to run in the background. This is normally to allow media apps to continue playing music when the app is sent to the background. However if you are careful you can get it to do other thing in there too.
In your plist under "Required Background Modes" add a key "Item 0" and set it to "App plays Audio". This will mean you can do it.
You will then have to using AVAudioPlayer, play a silent sound that is say 5mins long, and then register one of your controllers for the AVPlayerItemDidPlayToEndTimeNotification notification. Then when this calls back, you can have your bit of code that, first takes a screenshot, and then starts the sound again.
This is the general concept, look somewhere like :
http://mobile.tutsplus.com/tutorials/iphone/ios-sdk_background-audio/
for how to set up the audio playing.
Just a note: APPLE WILL REJECT THIS!
If you are making an app for personal use only, this is fine, but will never make it to the app store.
Hoep this sheds some light on your situation! :)
When press the lock button in app,system will call :
-(void) applicationWillResignActive:(UIApplication *)application and
-(void) applicationDidEnterBackground:(UIApplication *)application
So how can I do to make my app only resignActive but not enter background,and I can run my timer when screen locked(Timer can't execute in background mode).
One method is set the property "Application does not run in background" in .plist to YES,it worked, but my app can never enter background again,however I want it will enter background when press the home button.
Update: I want to play some music in my app at a certain time,just like a music alarm,and I still want it works fine when the screen locked,because keep the screen on may waste a lot of battery,and I don't need to do any thing when user press the home button and exit my app.
Open your Info.plist file and add Application does not run in background. Set value to YES.
Application must have special privileges to do any processing in background such as Audio service/Voip service/Location service.
"I can run my timer when screen locked(Timer can't execute in background mode)"
you cannot run a timer in background which will keep running without using any tentrum and doing so...apple will not accept your application on appstore - that's the worst side if you are targeting appstore...
You can not prevent your app from entering the background. This is decided by the operating system (iOS) and is out of control from applications. However, from reading your updated question, I don't think this is what you need to do.
You can execute background tasks with [UIApplication beginBackgroundTaskWithExpirationHandler;] (see reference). If you want to have something happening after a certain interval, check out [UIApplication scheduleLocalNotification:].
Some services such as VOIP, Audio and CoreLocation are allowed to run in background. Using these for other than their intended purposes (for example, playing silent audio) may risk your app being rejected.
Note that there is nothing you can do to prevent your application from entering the background. It is just that some tasks are allowed to execute in the background. Because of this, you cannot do GUI operations and NSTimers will probably not fire (at least I know some cases where they don't).
It would help knowing what you want to run in the background in order to suggest a solution.
Unless you are playing audio BEFORE the move to background you cannot start audio playback when the app is moved to the background or the screen is locked (which has some weird specifics) suffice to say, its as if you were in the background without actually receiving the applicationDidEnterBackground notification.
The best you can do is schedule a local notification, but in this case your music is limited to 30 seconds and must be part of your application bundle.
I have an alarm clock app which works on a timer. When the alarm is meant to go off and the screen is switched off, it should start playing audio from AVAudioPlayer, but it doesn't. Then when i turn the screen back on, i can see that the rest of the code fired as expected (a stop button is now on the screen). How do i get the AVAudioPlayer to play when the screen is turned off?
Is there any way for me to detect that the screen is turned off?
#zoul is correct that using the default audio session category will result in sound form your app being disabled when the user locks the screen. See the Audio Session Programming Guide for direction on which audio session category you should choose.
However, even once your audio session category is set correctly, you'll have another issue to tackle. When the screen is switched off, your application gets suspended per Apple's documentation here: Executing Code in the Background. This means that when the user locks their phone or switches to a different app, your app will stop running and stay in a freeze-dried (task-suspended) state until the user activates your app again. At that point, your app resumes execution as if nothing happened. That's why it appears that your app has continued to function when you unlock the screen.
For alarm behavior, you'll probably want to schedule the delivery of a local notification. A local notification will ensure that the system provides your alert to the user at the time you request, and allows the user to activate your app. See Scheduling the Delivery of Local Notifications for details on how to accomplish this.
Maybe you have the wrong audio category? See the documentation for AVAudioSession, especially the audio category settings.
I am developing an iphone app which uses background audio (on an infinite loop) to continue playing after the app has entered the background.
My problem is I want to implement a "sleep timer" which stops playback after a specified period of time.
Is this possible? I have spent an hour looking for a method to do this with no avail.
EDIT: My current thought is to use a lower level API, the Audio Queue Services, and manually re-fill the queue with another instance of the loop during the AudioQueueOutputCallback. If the timer has expired I do not fill the loop. I'm assuming this should work since the documentation says audio callbacks are still fired when an app is playing multitasking background audio. Can anyone think of a better way or a reason why this wouldn't work?
While you queue sound data on the background your app remains fully functional and running as if it was in the foreground (well almost), so yes, you should just write a timer that stops the playback at a given time and it will be fired as expected.
Now to the second question: once you stop queueing things up, your app will be "frozen" until the user manually brings it to the foreground... So what you should do is start queueing audio data from the second file before the first one is done playing, and if you DO need to pause or stop, maybe a solution is to play 0 bytes (silence)?
I'm not actually sure this would be allowed in the App Store. An app is not allowed to execute at all in the background, with the exception of VoIP apps and push notifications.
I understand that applicationWillTerminate is no longer called in iOS4, practically. But I have this situation:
my audiobook goes in background mode and keeps playing audio;
until version 3.x of SDK I saved the point where one listened to the MP3 file, in applicationWillTerminate;
now I was told to keep this saving in applicationWillTerminate (for iPhone 3G) and to implement the same method in applicationDidEnterBackground: but this saves NOT the point where user was at the end, just the point when he entered the background...
But, which is the moment, or better the invoked method, where user exits the application from the application dock? Does this exist?
ApplicationWillTerminate is called when there is a memory problem, but really I can't figure what happens when the user himself shuts down the app.
I repeat: applicationDidEnterBackground does not help me because when the user enters in background mode, he can stays in this position for a long time listening to the audiobook and when he starts again the app, after this is shut down, I mean, he will find the position of the audio file when he entered the background mode…
I'm really confused…
Thanks for your help!
You should save the play location automatically in applicationWillResignActive:, applicationDidEnterBackground: regardless of whether the audio keeps playing or not. Then put another save in applicationWillTerminate. That way the last play location is saved regardless of what happens next. The next event simply overwrites the saved play location to update it.
An even better option would be to have the audio player object itself trigger the save whenever it is interrupted e.g [AVAudioPlayerDelegate audioPlayerBeginInterruption:] or similar. It might takes some extra work but it would guarantee that the play location was always saved regardless of the cause of the interruption.