[iOS] JS doesn't keep running in background if it's production build #25083
Description
I have an editor app that syncs with server. I would like to keep it running for a few seconds to finish syncing after it becomes inactive in background.
I managed to do that by adding following code to AppDelegate.m:
- (void)applicationDidEnterBackground:(UIApplication *)application
{
UIBackgroundTaskIdentifier taskId = [application beginBackgroundTaskWithExpirationHandler:nil];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// do nothing for 4.7 seconds
[NSThread sleepForTimeInterval:4.7f];
[application endBackgroundTask:taskId];
});
}While it works well in debug build, I encountered that it does not work in production build (TestFlight).
Seems like JS stops immediately after becoming inactive whereas the background task runs as expected on native side.
I suspect it's a bug and tried to fix but couldn't.
Could you help me out? Where should I look into?
I'm happy to contribute.
React Native version: 0.59.2
react-native info
info
React Native Environment Info:
System:
OS: macOS 10.14.5
CPU: (8) x64 Intel(R) Core(TM) i7-7700K CPU @ 4.20GHz
Memory: 21.46 GB / 56.00 GB
Shell: 3.0.2 - /usr/local/bin/fish
Binaries:
Node: 11.12.0 - ~/.nvm/versions/node/v11.12.0/bin/node
Yarn: 1.13.0 - /usr/local/bin/yarn
npm: 6.9.0 - ~/.nvm/versions/node/v11.12.0/bin/npm
Watchman: 4.9.0 - /usr/local/bin/watchman
SDKs:
iOS SDK:
Platforms: iOS 12.2, macOS 10.14, tvOS 12.2, watchOS 5.2
Android SDK:
API Levels: 22, 23, 25, 26, 27, 28
Build Tools: 23.0.1, 25.0.2, 26.0.1, 26.0.3, 27.0.3, 28.0.3
System Images: android-22 | Google APIs Intel x86 Atom, android-26 | Google Play Intel x86 Atom, android-27 | Google APIs Intel x86 Atom, android-27 | Google Play Intel x86 Atom, android-28 | Google Play Intel x86 Atom, android-Q | Google Play Intel x86 Atom
IDEs:
Android Studio: 3.4 AI-183.6156.11.34.5522156
Xcode: 10.2.1/10E1001 - /usr/bin/xcodebuild
npmPackages:
react: 16.8.3 => 16.8.3
react-native: 0.59.2 => 0.59.2
npmGlobalPackages:
react-native-cli: 2.0.1
Steps To Reproduce
- Implement a background task in your
AppDelegate.m:
- (void)applicationDidEnterBackground:(UIApplication *)application
{
UIBackgroundTaskIdentifier taskId = [application beginBackgroundTaskWithExpirationHandler:nil];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[NSThread sleepForTimeInterval:4.7f];
[application endBackgroundTask:taskId];
});
}- Add a following code to your
App.js:
AppState.addEventListener('change', (nextAppState) => {
if (nextAppState === 'background') {
setTimeout(() => {
fetch('<Somewhere you can watch requests>')
}, 2000)
}
})- Replace
<Somewhere you can watch requests>with a proper URL
Make sure App Transport Security Settings is correctly configured if the URL is not HTTPS.
- Run it via TestFlight
Describe what you expected to happen:
It issues a HTTP request after 2 seconds when going to background.
Thanks in advance!