Switching avaudiosession categories then retaking

问题:

This is my first post asking a question as i never usually need help but i can't figure out if this is even possible. What i need is to switch between these two categories of avaudiosession and when the switch is made from mixing allowed to no mixing for the app take back control of the remote controls in the control center.

1. [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback withOptions:AVAudioSessionCategoryOptionMixWithOthers error:nil]

and

1. [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback withOptions:nil error:nil]

Ill try explain what is occurring:

They both work independently so if i start with the first avaudiosession config it allows mixing and correctly switches the remote controls in the control center to iPod.

And if i start the second avaudiosession config the app correctly takes control of the remote control in the control center.

The issue occurs when i trying toggle these options. When i toggle the app doesn't retake control of the remote controls after mixing is turned off.

Any help would be greatly appreciated

回答1:

I've found a solution that works for me, which involves calling

[[UIApplication sharedApplication] beginReceivingRemoteControlEvents]

or

[[UIApplication sharedApplication] endReceivingRemoteControlEvents]

before setting AVAudioSession category options. eg:

NSUInteger options = ... // determine your options

// it seems that calls to beginReceivingRemoteControlEvents and endReceivingRemoteControlEvents
// need to be balanced, so we keep track of the current state in _isReceivingRemoteControlEvents

BOOL shouldBeReceivingRemoteControlEvents = ( 0 == (options & AVAudioSessionCategoryOptionMixWithOthers) );

if(_isReceivingRemoteControlEvents != shouldBeReceivingRemoteControlEvents) {
    if(shouldBeReceivingRemoteControlEvents) {
        [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
        _isReceivingRemoteControlEvents=YES;
    } else {
        [[UIApplication sharedApplication] endReceivingRemoteControlEvents];
        _isReceivingRemoteControlEvents=NO;
    }
}

[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback withOptions:options error:&error];

...

[[AVAudioSession sharedInstance] setActive:YES error:&error]

I've been able to achieve consistent results by using a variable to keep track of whether or not the app is currently receiving remote control events so that I can ensure that calls to (begin/end)ReceivingRemoteControlEvents are balanced. I haven't found any documentation that says that you need to do this but otherwise things don't always seem to behave as expected, particularly since I call this code multiple times throughout the course of the application.

In my implementation, the code above gets called each time the app comes to the foreground and also just before each time I begin playing audio.

I hope this helps.