Play a background sound in WatchKit app - ios

Question

I have a button in WatchKit that sends a notification to the main iPhone app like this.
-(IBAction) startSound
{
//turn sound on
NSString *requestString = [NSString stringWithFormat:#"startSound"]; // This string is arbitrary, just must match here and at the iPhone side of the implementation.
NSDictionary *applicationData = [[NSDictionary alloc] initWithObjects:#[requestString] forKeys:#[#"startSound"]];
[WKInterfaceController openParentApplication:applicationData reply:^(NSDictionary *replyInfo, NSError *error) {
//NSLog(#"\nReply info: %#\nError: %#",replyInfo, error);
}];
}
In my iPhone app delegate I have added the following code.
- (void)application:(UIApplication *)application handleWatchKitExtensionRequest:(NSDictionary *)userInfo reply:(void(^)(NSDictionary *replyInfo))reply
{
NSLog(#"handleWatchKitExtensionRequest ...");
NSMutableDictionary *mutDic = [[NSMutableDictionary alloc] init];
//This block just asks the code put after it to be run in background for 10 mins max
__block UIBackgroundTaskIdentifier bgTask;
bgTask = [application beginBackgroundTaskWithName:#"MyTask" expirationHandler:^{
bgTask = UIBackgroundTaskInvalid;
}];
NSString *request = [userInfo objectForKey:#"startSound"];
if ([request isEqualToString:#"startSound"])
{
NSString *soundFilePath = [[NSBundle mainBundle] pathForResource: #"warning" ofType: #"mp3"];
NSURL *fileURL = [[NSURL alloc] initFileURLWithPath: soundFilePath];
myAudioPlayer1 = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error:nil];
myAudioPlayer1.numberOfLoops = -1; //inifinite
[myAudioPlayer1 play];
}
reply(nil); //must reply with something no matter what
//once code is all done and the reply has been sent only then end the bg-handler
[application endBackgroundTask:bgTask];
}
Yet, when my app went for apple review, it got rejected for reasons that my app had to be running in the foreground for the sound feature to work. What did I miss?
10.6 - Apple and our customers place a high value on simple, refined, creative, well thought through interfaces. They take more work but are
worth it. Apple sets a high bar. If your user interface is complex or
less than very good, it may be rejected
10.6 Details
We still found that your Apple Watch app requires the containing app
to be running in the foreground on iPhone in order to play siren
sounds, which provides a poor user experience.
Next Steps
Please see the UIApplicationDelegate Protocol Reference to implement
this method and use it to respond to requests from the Apple Watch
app.
Because this method is likely to be called while your app is in the
background, call the beginBackgroundTaskWithName:expirationHandler:
method at the start of your implementation and the endBackgroundTask:
method after you have processed the reply and executed the reply
block. Starting a background task ensures that your app is not
suspended before it has a chance to send its reply.

Answer 1

How long is the audio clip? In the code you've shared it looks like reply() would be called almost immediately, which wouldn't give the clip a chance to play. You should delay calling reply() until your audio clip has completed.

Answer 2

I do something very similar in my WatchKit app. When the user taps on a button I play audio from my iPhone app and my iPhone app does not need to foreground for it to work. There were two things I had to do to get it to work. The first was setting up a background task with beginBackgroundTaskWithName, which I can see you are doing. The second was to enable background audio capabilities in my background modes.
I don't remember doing anything other than those two to get it to work. I did already have background audio working in my app before I added support so it could be controlled with MPNowPlayingInfoCenter.