How to stop MPMusicPlayerController from enabling

问题:

I have an application that requires the iPhone screen to remain active (or not, depending on user choice). I've done this by disabling the application idle timer, which works fine and dandy until I start playing media via the MPMusicPlayerController. Due to a bug in the SDK, this then reenables the idle timer with no apparent way to disable it again.

My app flow is:

1. App starts
2. Screen stays on
3. <...time passes...>
4. Play audio file
5. Idle timer kicks in
6. Screen turns off

I have an empty audio file playing in the background to stop the phone going into deep sleep, but I'd really like to keep the screen unlocked too.

Has anyone managed to figure out a workaround for this?

回答1:

I had a similiar problem, and found a fix for it. The fix might work for you too:

I call a method periodically (every 10 seconds), which sets idleTimerDisabled first to NO, then to YES.

- (void)calledEveryTenSeconds
{
    [UIApplication sharedApplication].idleTimerDisabled = NO;
    [UIApplication sharedApplication].idleTimerDisabled = YES;
}

Only setting to YES alone does not fix the problem. It seems the property has to change first to be recognized by UIApplication.

My problem was, that the screen kept turning dark as soon as I switched music tracks on the iPod player via the headphone remote. My guess is, that this is the same issue as you are experiencing.

回答2:

I found a solution to this problem. Invoke a method that disables the idleTimer in about 5 seconds after you start playing the music. It's a bit of a hack, but it is a workaround.

[[SoundEngine mainEngine] playMusic];

[self performSelector:@selector(setIdleTimeDisabled) withObject:nil afterDelay:5.0];

- (void) setIdleTimeDisabled {
[UIApplication sharedApplication].idleTimerDisabled = YES;
NSLog(@"Setting idleTimer to TRUE");}

回答3:

You should simply turn off the idle timer. What I usually do in a viewcontroller that needs to stay 'awake' is this:

- (void) viewWillAppear:(BOOL)animated
{
    [[UIApplication sharedApplication] setIdleTimerDisabled: YES];
}

- (void) viewWillDisappear: (BOOL) animated
{
    [[UIApplication sharedApplication] setIdleTimerDisabled: NO];
}

This will make sure the screen will not get locked due to user inactivity.