[FIX] #134 addVolumeListener is not triggered on iOS 15

[Igor-Tiukavkin]

Issue

Number #134: iOS 15 addVolumeListener fix

The system volume observer is no longer working on iOS 15.

Steps for reproduce:

1. Add system volume did change observer
2. Play any media
3. Change volume with hardware buttons at the device
4. Change volume with volume control in the app

Expected behaviour:
Change of volume setting value is processed correctly

Current Result:
Hardware buttons volume change has no response.
NotificationCenter produces no notifications for key AVSystemController_SystemVolumeDidChangeNotification.

Problem:

There is an information on stackoverflow that observing of AVSystemController_SystemVolumeDidChangeNotification is no longer supported because it's a private API.

Solution

The solution is based on the answer: EWTDTHK2 commented on 3 Oct.
The correct approach is to add KVO observer for AVAudioSession instance for outputVolume keyPath.

[MrHjalmarsson]

Thanks for a very useful package!
Does anyone have an idea about when this PR will be merged?
Would be greatly appreciated if it could happen rather sooner than later. :)

[Shummy1991]

You can use patch-package until it is merged.

[MrHjalmarsson]

Thanks, @Shummy1991! Will try that!

[kot331107]

cool that you introduced dealloc() and removed the subscription in it 👍 I did same in our project as a band-aid/patch-package and found your solution later. Good job!

[kot331107]

lgtm

[kolking]

@c19354837 please publish a new release with this fix included.

[buildgreatthings]

@c19354837 please publish a new release with this fix included.

[kot331107]

@awcchungster would patch-package work with you till guys won't publish it?

[arjun-mavonic]

This doesn't work if the app goes into background and then into foreground.