I know that iOS normally suspends the app on going to background. And there are ways to continue execution mentioned here.
But I found an app Saavn, which continues to download even after going to background.
Although it's a music app, but for audio service to run on background an audio must be playing. And it continues downloading even if no audio is playing.
This also can't be done through beginBackgroundTaskWithExpirationHandler:, as it only allows completion of a single fixed-length task. But in this app it continues to download infinitely till the whole playlist is downloaded.
And I also don't think it would be UIBackgroundModes = fetch because it downloads very large playlists with hundreds of songs(which are definately not samll fetches).
So, is there any other way to continue background execution(without violating apple's policies), NOT mentioned in Apple's developer's reference?
Please refer this documentation, it explains different scenarios https://developer.apple.com/library/ios/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/BackgroundExecution/BackgroundExecution.html
Related
TLDR: How to jumpstart a webviews audioSession without reloading its content?
Hello everyone. I am having a very specific issue with the wkwebview on iOS in regards to the AudioSession.Category management. I guess I start with that it is well understood that the wkwebview operates on its own process and therefor owns its own AudioSession. That means that any changes on the APPs AudioSession won't reflect on the webviews AudioSession.
We build an app, which is entirely web based and has to be for reasons I don't want to go into, so our IOS app is essentially a wrapper for the web content. Recent web content required us to use webrtc functionality do do audio recordings which is only available from iOS 14.3 upwards, which required us to work out a solution, which is backwards compatible down to iOS 12. The idea was to create a native audio recorder, which then interfaces with the webview to transfer audio recordings to the web content.
In order to make recordings within the app the AudioSession.Category needs to change to playAndRecord and is triggered by the webviews content through the messageHandler interface. A change of the APP category will trigger an interruption of the webview audioSession, which from then on does not play any media anymore (until a new url is loaded(single page apps do not make new requests in general)). To fix this a reload of the current url is needed to un-interrupted the sound, which can be somewhat masked behind loading screens but isn't a really good solution.
I am looking for ways to start the audio again without reloading the webview.
Thanks for any insights on this.
I've recently stuck with similar problem. Here is what I've found.
Whenever background music like YouTube in WKWebView or Music app is playing and your app audio session category or mode (but not options [1]) is changed while app's audio session is active background audio is interrupted. Even when re-configuration of audio session is happen between mixable configurations. The solution I've found is to deactivate app audio session prior applying new configuration and activating it again. And in case of playAndRecord it is important not to forget to add [.mixWithOthers]/[.mixWithOthers, .duckOthers] option. For some reason I can't find formal documentation on this behavior but confirmed it with simple demo app which provide manual way to activate/deactivate audio session and configure it to variety of category/mode/options.
[1] It is possible to switch between [.mixWithOthers] and [.mixWithOthers, .duckOthers] on active audio session and not to interrupt background audio, if category and mode are not changed during reconfiguration.
I'm doing some audio streaming with iOS 7's Multipeer Connectivity framework. The streaming works well, but when I put the app on background it stops working.
Someone can tell me if this is a framework limitation, or I'm doing something wrong?
And, if it is a framework limitation, is it possible to do something to avoid this?
Can I use Background Tasks, to keep streaming and music working on background?
Is possible do this? If is not possible, do any alternatives exist for MultiPeer audio streaming between iOS devices?.
I´m using this example: https://github.com/tonyd256/TDAudioStreamer.
Explained on this page: http://robots.thoughtbot.com/streaming-audio-to-multiple-listeners-via-ios-multipeer-connectivity.
Thanks a lot!
On the Apple documentation for playing audio in the background (scroll down a bit). Some relevant paragraphs:
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 or recording audio content, the app continues to run in the background. However, if recording or playback stops, the system suspends the app.
You can use any of the system audio frameworks to work with background audio content, and the process for using those frameworks is unchanged.
This means that iOS should recognize that you're playing audio through Core Audio, and keep your app unsuspended, as long as you've correctly configured your app for playing audio in the background.
Because your app is not suspended while playing media files, callbacks operate normally while your app is in the background. In your callbacks, though, you should do only the work necessary to provide data for playback. For example, a streaming audio app would need to download the music stream data from its server and push the current audio samples out for playback. Apps should not perform any extraneous tasks that are unrelated to playback.
You should be able to operate normally as long as your app is still playing audio, and is allowed to do what it needs to in order to continue playing audio. This means that you should be able to continue to use MPC in the background to receive the audio data and play it.
Be sure to read the entire documentation on the subject, especially regarding Audio Sessions.
iOS devices get limited cpu cycles for explicit purposes when they have been backgrounded by the user.
According to Apple's documentation on multitasking and execution in the background, the following types of apps are supported, but have to be explicitly declared:
Apps that play audible content to the user while in the background, such as a music player app
Apps that record audio content while in the background.
Apps that keep users informed of their location at all times, such as a navigation app
Apps that support Voice over Internet Protocol (VoIP)
Apps that need to download and process new content regularly
Apps that receive regular updates from external accessories
Your case falls under Apps that play audible content to the user while in the background, such as a music player app. You can find more information from the link provided above.
I have my v 1.1 of my app (iphone) which has been rejected from Apple.
Reasons for rejection:
2.16
We found that your app uses a background mode but does not include
functionality that requires that mode to run persistently. This
behavior is not in compliance with the App Store Review Guidelines.
We noticed your app declares support for audio in the
UIBackgroundModes key in your Info.plist, but no audible content is
played when the application is in the background. While your intention
may have been to provide this functionality, at the time of review, we
were not able to play background audio for your app.
As indicated in the iOS Application Programming Guide: "This key is
intended for use by applications that provide audible content to the
user while in the background, such as music-player or streaming-audio
applications." Therefore, it would be appropriate to provide audible
content to the user while the app is in the background or remove the
"audio" setting from the UIBackgroundModes key.
In the v 1.0 which has been accepted the required background mode "App audio plays" was already enable.
When I launch one sound of my app the sound is played and I when click on the lock screen the sound continues to be played in background.
In the new version (v1.1) I added the function which detects when I push the button Home of the iPhone. If the button home is pressed so the sound is paused.
When i try on my device it's run correctly and without bug.
So I don't understand exactly what is the problem with my app?
If you're pausing the sound when you hit the home button, then you aren't playing a sound in the background. Either change your app so that it plays sound in the background all the time, or email Apple and explain that your app needs the background functionality so that it can play while the phone is locked.
I'm not sure but you might be able to play the sound during the lock screen without audio background mode. Try removing it and see if your app behaves the same. If it does, then you should remove the key (no reason to have it).
If you use the audio background mode, your app has to play continuous audio (like the Music app, or Downcast for example). Is that what yours does? Or does it just play a sound briefly?
You should be able to play a short sound (< 10 mins) by using beginBackgroundTaskWithExpirationHandler: (I think!)
See below the answer to my Question from Apple :
Jul 31, 2012 10:21 AM. From Apple.
Hello,
Thank you for providing this information. However, in order to ensure that the audio background feature is properly implemented, it would be appropriate to press on the home button once the audio is launched.
For more information on how to implement this feature, please refer to iOS Application Programming Guide
Please make necessary change to resolve this issue.
So my application for iphone4 reads data from the accelerometer and sends it to another application via tcp sockets. I need my app to work in background mode, so what I did was:
I put an mp3 file in the application's Documents folder
I used AVAudioPlayer library to play the file in a loop. It works.
I edited Info.plist and added option "required background
modes" with "audio" on.
Still, the scheduler suspends the application whenever I press the iphone's home button. Is there anything I missed?
I read apple's documentation, but I didn't find a solution. A few thoughts on this:
do I have to edit appDelegate.m?
is it because I use AVAudioPlayer instead of the iPod?
is it because I play an audio file from the application documents
folder?
I read about one person changing iOS Development Target from 4.0 to
3.2.1, but that didn't work for me.
And finally, say I get this to work, would the application still be getting data from the accelerometer?
On a side note, I don't want to submit the application to the App Store.
No, you will not receive accelerometer notifications in background mode. As far as I know, it is not possible. Check Executing Code in Background.
If you read the docs carefully, you will know that the whole background code model is based on responding to specific events (location and voip modes).
As for the audio mode here is an extract from Apple:
Your application should limit itself to doing only the work necessary
to provide data for playback while in the background. For example, a
streaming audio application would download any new data from its
server and push the current audio samples out for playback. You should
not perform any extraneous tasks that are unrelated to playing the
content.
Not sure whether you have solved your issue or not since this question was posted more than one year ago. Also, not sure whether playing audio is a must in your app or not. If both answers are no, my recent investigation may help a bit.
Here are how I get my app getting accelerometer data at the background
1. Follow this tutorial http://mobile.tutsplus.com/tutorials/iphone/ios-multitasking-background-location/ to get the background location working.
2. Follow this tutorial http://jonathanhui.com/ios-motion to get the accelerometer working.
Then you can get an app collecting accelerometer data at the background. Hope this helps.
I need to be able to play a sound while running the application in the background.
I tried with UILocalNotifications but the file needs to be part of the bundle, and that will not be the case, as I need to generate the sound files on the fly...
So is there any way that I can play a sound while running in the background?
Thanks.
You can't, unless you continuously play audio and have the appropriate audio session category set for your app... then your app doesn't go to sleep, it continues to run (again so long as audio is playing).
This is part of the design limitations of iOS multitasking.
Apple has allowed people to get away with having a continuously looping blank audio file (AVAudioPlayer loop = -1 with a 1-sec blank CAF file) if the app is primarily audio related and it is obvious to the user that this has battery life implications (and can be disabled by the user), but YMMV... you app can also be rejected for this.