[expo-av][iOS] Lock screen controls not working

🐛 Bug Report

I am using react-native-music-control for lock screen controls when playing audio in background mode. The pause button on the lock screen works, but when play is pressed again, it does not resume playing. When the function that listens to the lock screen play button press runs, it says that there is no active sound session.

A a workaround, having this function: https://github.com/expo/expo/blob/491dde5dedca1a95efa40026aa119a0b0ec2b4e5/packages/expo-av/ios/EXAV/EXAVPlayerData.m#L359 always return true results in the lock screen controls working.

The app I am working on is already in production. Is it safe to use this workaround as a temporary fix to get lock screen controls working?

Environment

Expo CLI 2.17.1 environment info: System: OS: macOS 10.14.4 Shell: 5.3 - /bin/zsh Binaries: Node: 11.10.1 - ~/.nvm/versions/node/v11.10.1/bin/node Yarn: 1.15.2 - /usr/local/bin/yarn npm: 6.7.0 - ~/.nvm/versions/node/v11.10.1/bin/npm Watchman: 4.9.4 - /usr/local/bin/watchman IDEs: Android Studio: 3.4 AI-183.5429.30.34.5452501 Xcode: 10.2.1/10E1001 - /usr/bin/xcodebuild npmPackages: react: 16.8.3 => 16.8.3 react-native: 0.59.5 => 0.59.5 react-navigation: 3.9.1 => 3.9.1 npmGlobalPackages: expo-cli: 2.17.1

iOS

Steps to Reproduce

Create new app with bare template -> add react-native-music-control as dependency -> configure MusicControl.on('play', ...) and MusicControl.on('pause', ...) and other required configurations -> play a sound -> whilst sound is playing lock the device -> on the lock screen press pause -> on the lock screen press play, this should print no active sound session… to error log

Expected Behavior

In the section above, the last step should resume the paused sound, rather than printing an error to the log

Actual Behavior

The last step two section above, i.e. printing to the error log that there is no active av session

Reproducible Demo

https://github.com/redpandatronicsuk/expoavtest

[brettdh]

Perfect, thank you! I found the wonderful patch-package tool and saved your second patch for now. ✨

[IjzerenHein]

I’ve been debugging this to see whether we can get this fixed. What I’ve found so far is that with the latest expo-av it doesn’t work because of this check in promoteAudioSessionIfNecessary in EXAM.m:

if (_isBackgrounded && ![_kernelAudioSessionManagerDelegate isActiveForModule:self]) {
  return UMErrorWithMessage(@"This experience is currently in the background, so the audio session could not be activated.");
}

This check does not allow audio to be played when the app is in the background. When disabling this check it starts working though. Nevertheless this check serves a purpose and we cannot just disable it. More research and a solid approach for triggering audio in the background is needed. To be continued…