Restore MPMoviePlayerController controls autohide behavior after unlocking a device

FixMPMoviePlayerControllerControlsAutohide.m

/**
 *  Locking then unlocking a device while a movie is playing disables controls autohiding.
 *  `MPInlineVideoController` registers for the (private) UIApplicationResumedEventsOnlyNotification
 *  (which is sent between UIApplicationWillEnterForegroundNotification and UIApplicationDidBecomeActiveNotification).
 *  In its callback (-[MPInlineVideoController _applicationResumedEventsOnly:]) it calls `[self setDisableControlsAutohide:YES]`
 *  effectively disabling controls autohide. In order to restore the automatic hiding of controls, we call
 *  setDisableControlsAutohide:NO when UIApplicationDidBecomeActiveNotification is posted.
 */

#import <MediaPlayer/MediaPlayer.h>

static void EnableControlsAutohide(MPMoviePlayerController *moviePlayerController)
{
	NSString *videoViewController = [@[ @"video", @"View", @"Controller" ] componentsJoinedByString:@""];
	NSString *inlineVideoControllerKeyPath = [@[ @"implementation", videoViewController ] componentsJoinedByString:@"."];
	@try
	{
		id inlineVideoController = [moviePlayerController valueForKeyPath:inlineVideoControllerKeyPath];
		SEL selector = NSSelectorFromString([@[ @"set", @"Disable", @"Controls", @"Autohide", @":" ] componentsJoinedByString:@""]);
		NSMethodSignature *methodSignature = [inlineVideoController methodSignatureForSelector:selector];
		if (methodSignature.numberOfArguments != 3)
			return;
		
		const char *returnType = methodSignature.methodReturnType;
		const char *firstArgType = [methodSignature getArgumentTypeAtIndex:2];
		if (strcmp(returnType, @encode(void)) == 0 && strcmp(firstArgType, @encode(BOOL)) == 0)
		{
			// Equivalent to [inlineVideoController setDisableControlsAutohide:NO], i.e. enable controls autohide which is the default behavior
			NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:methodSignature];
			[invocation setTarget:inlineVideoController];
			[invocation setSelector:selector];
			BOOL disableControlsAutohide = NO;
			[invocation setArgument:&disableControlsAutohide atIndex:2];
			[invocation invoke];
		}
	}
	@catch (NSException *exception)
	{
		NSLog(@"%@", exception);
	}
}

@implementation NSObject (FixMPMoviePlayerControllerControlsAutohide)

+ (void) load
{
	static __weak MPMoviePlayerController *currentMoviePlayerController;
	
	dispatch_async(dispatch_get_main_queue(), ^{
		NSNotificationCenter *defaultCenter = [NSNotificationCenter defaultCenter];
		NSOperationQueue *mainQueue = [NSOperationQueue mainQueue];
		
		[defaultCenter addObserverForName:MPMoviePlayerNowPlayingMovieDidChangeNotification object:nil queue:mainQueue usingBlock:^(NSNotification *notification) {
			currentMoviePlayerController = notification.object;
		}];
		[defaultCenter addObserverForName:MPMoviePlayerPlaybackDidFinishNotification object:nil queue:mainQueue usingBlock:^(NSNotification *notification) {
			currentMoviePlayerController = nil;
		}];
		
		[defaultCenter addObserverForName:UIApplicationDidBecomeActiveNotification object:nil queue:mainQueue usingBlock:^(NSNotification *notification) {
			MPMoviePlayerController *moviePlayerController = currentMoviePlayerController;
			if (moviePlayerController)
				EnableControlsAutohide(moviePlayerController);
		}];
	});
}

@end