在 iOS 7 和 8 中通过 AVPlayer 使用远程控制

Question

我正在尝试编写一个简单的个人广播应用程序，但遇到了一个烦人的问题。

我尝试使用 AVPlayer 从远程服务器播放 .pls（流）文件，我成功地使其工作。我现在可以播放流，但正如我在标题中提到的，当应用程序处于后台时，我无法远程控制播放/暂停选项。

我在互联网上搜索了很多关于该主题的内容，并找到了两种解决方案。

1- 就像在 Apple 的远程控制事件文档中一样，使用“MPRemoteCommandCenter”类来处理这个问题，但是对于这个解决方案，我找不到任何很好的解释来说明我将如何使用 AVPlayer。这让我想到了第二个解决方案，因为我不知道如何使用 MPRemoteCommandCenter 类。

2- 几乎所有人都提到过 remoteControlReceivedWithEvent:方法。但是，当我尝试使用这种方法时，我无法得到回应。我的remoteControlReceivedWithEvent:方法从未被调用过。这是我如何实现行为的代码：

我有两个类，一个叫做 EGPlayRadio.m，它包含 AVPlayer 和 AVAudioSession 的东西，另一个是 EGMainMenuViewController.m，它显示一个播放按钮和暂停按钮来播放广播。

• 我祈祷，注意第一次调用[AVSession sharedInstance]之前调用[[UIApplication的sharedApplication] beginReceivingRemoteControlEvents]方法。

• 我还注意到从项目的构建设置中授予应用程序后台音频播放权限。

但是，在互联网上搜索了很多之后，我找不到适合我的问题的解决方案。这是我实现的两个类：

EGPlayRadio.m

#import "EGPlayRadio.h"
#import <MediaPlayer/MediaPlayer.h>
#import <AVFoundation/AVFoundation.h>

@interface EGPlayRadio () <AVAudioPlayerDelegate>

@property (nonatomic, strong) AVAudioSession *audioSession;
@property (nonatomic, strong) AVPlayer *player;

@end

@implementation EGPlayRadio

- (id)initDefault
{
    self = [super init];
    if (self)
    {
        _audioSession = [AVAudioSession sharedInstance];
        [_audioSession setCategory:AVAudioSessionCategoryPlayAndRecord withOptions:AVAudioSessionCategoryOptionDefaultToSpeaker error:nil];
        [[AVAudioSession sharedInstance] setActive: YES error: nil];
        [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback withOptions:AVAudioSessionCategoryOptionMixWithOthers error:nil];
        NSURL *url = [[NSURL alloc] initWithString:@"http://LINK-OF-THE-PLS-FILE"];
        _player = [[AVPlayer alloc] initWithURL:url];
    }
    return self;
}

- (void)playRadio
{
    [self.player play];
}

- (void)pauseRadio
{
    [self.player pause];
}

EGMainMenuViewController.m

@interface EGRMainMenuViewController ()

@property (nonatomic, strong) IBOutlet UIButton *playButton;
@property (nonatomic, strong) IBOutlet UIButton *pauseButton;
@property (nonatomic, strong) EGPlayRadio *radioControl;

@end

@implementation EGRMainMenuViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.radioControl = [[EGPlayRadio alloc] initDefault];
    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
    [self becomeFirstResponder];
    self.pauseButton.enabled = NO;
    self.pauseButton.alpha = 0.3f;
}

- (BOOL)canBecomeFirstResponder
{
    return YES;
}

- (IBAction)musicInteracted:(id)sender
{
    if (sender == self.playButton)
    {
        self.pauseButton.enabled = YES;
        self.pauseButton.alpha = 1.0f;
        self.playButton.enabled = NO;
        self.playButton.alpha = 0.3f;
        [self.radioControl playRadio];
    }
    else
    {
        self.pauseButton.enabled = NO;
        self.pauseButton.alpha = 0.3f;
        self.playButton.enabled = YES;
        self.playButton.alpha = 1.0f;
        [self.radioControl pauseRadio];
    }

}

-(void)remoteControlReceivedWithEvent:(UIEvent *)event
{
    switch (event.subtype) {
        case UIEventSubtypeRemoteControlTogglePlayPause:
            //[streamer pause];
            break;
        case UIEventSubtypeRemoteControlPlay:
            //[streamer start];
            break;
        case UIEventSubtypeRemoteControlPause:
            //[streamer pause];
            break;
        case UIEventSubtypeRemoteControlStop:
            //[streamer stop];
            break;
        default:
            break;
    }

}

@end

Answer 1

感谢@Onur ?ahindur，经过几年的努力，我终于有了这个工作。不敢相信这在任何地方都没有记录。正如 Onur 所说，stackoverflow 上有很多人都在为此苦苦挣扎，但这是第一个真正有效的解决方案。

我还使用“MPRemoteCommandCenter”类进行了此操作。我通过对管理我的 AVPlayer 的单例的方法调用实现了 appDelegate 中的所有内容。这是我的解决方案：

_audioSession = [AVAudioSession sharedInstance];

// Previously, I used [_audioSession setCategory:AVAudioSessionCategoryPlayback withOptions:AVAudioSessionCategoryOptionMixWithOthers error:&setCategoryError];
// As noted by @Onur, it has to be the following (without options)
[_audioSession setCategory:AVAudioSessionCategoryPlayback error:nil];

// Apple documentation says you don't need the following if you are using
// the MPRemoteCommandCenter, but that is not true. It is needed.
[[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
[self becomeFirstResponder];


MPRemoteCommandCenter *commandCenter = [MPRemoteCommandCenter sharedCommandCenter];
[commandCenter.togglePlayPauseCommand setEnabled:YES];
[commandCenter.playCommand setEnabled:YES];
[commandCenter.pauseCommand setEnabled:YES];
[commandCenter.nextTrackCommand setEnabled:YES];
[commandCenter.previousTrackCommand setEnabled:YES];
[commandCenter.togglePlayPauseCommand addTargetWithHandler: ^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {
    [[MediaController sharedInstance] playOrPauseMusic];    // Begin playing the current track.
    return MPRemoteCommandHandlerStatusSuccess;
}];

[commandCenter.playCommand addTargetWithHandler: ^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {
    [[MediaController sharedInstance] playOrPauseMusic];    // Begin playing the current track.
    return MPRemoteCommandHandlerStatusSuccess;
}];

[commandCenter.pauseCommand addTargetWithHandler: ^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {
    [[MediaController sharedInstance] playOrPauseMusic];    // Begin playing the current track.
    return MPRemoteCommandHandlerStatusSuccess;
}];

[commandCenter.nextTrackCommand addTargetWithHandler: ^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {
    [[MediaController sharedInstance] fastForward];    // forward to next track.
    return MPRemoteCommandHandlerStatusSuccess;
}];

[commandCenter.previousTrackCommand addTargetWithHandler: ^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {
    [[MediaController sharedInstance] rewind];    // back to previous track.
    return MPRemoteCommandHandlerStatusSuccess;
}];

[commandCenter.stopCommand setEnabled:NO];
[commandCenter.skipForwardCommand setEnabled:NO];
[commandCenter.skipBackwardCommand setEnabled:NO];
[commandCenter.enableLanguageOptionCommand setEnabled:NO];
[commandCenter.disableLanguageOptionCommand setEnabled:NO];
[commandCenter.changeRepeatModeCommand setEnabled:NO];
[commandCenter.changePlaybackRateCommand setEnabled:NO];
[commandCenter.changeShuffleModeCommand setEnabled:NO];
// Seek Commands
[commandCenter.seekForwardCommand setEnabled:NO];
[commandCenter.seekBackwardCommand setEnabled:NO];
[commandCenter.changePlaybackPositionCommand setEnabled:NO];
// Rating Command
[commandCenter.ratingCommand setEnabled:NO];

// Feedback Commands
// These are generalized to three distinct actions. Your application can provide
// additional context about these actions with the localizedTitle property in
// MPFeedbackCommand.
[commandCenter.likeCommand setEnabled:NO];
[commandCenter.dislikeCommand setEnabled:NO];
[commandCenter.bookmarkCommand setEnabled:NO];

除了上面的（我放在 appDelegate - application:didFinishLaunchingWithOptions 中）之外，还要将它添加到您的 appDelegate 中：

- (BOOL) canBecomeFirstResponder
{
    return YES;
}

然后，每次更改要播放的媒体项时，我都会从媒体控制器单例中执行以下代码：

ipodControlArtwork = [[MPMediaItemArtwork alloc]initWithImage:artworkImage];
if (artworkImage != nil && nowPlayingArtist != nil && nowPlayingTitle != nil && ipodControlArtwork != nil) {

    [MPNowPlayingInfoCenter defaultCenter].nowPlayingInfo = [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                                             nowPlayingTitle, MPMediaItemPropertyTitle,
                                                             nowPlayingArtist, MPMediaItemPropertyArtist,
                                                             ipodControlArtwork, MPMediaItemPropertyArtwork,
                                                             [NSNumber numberWithDouble:0.0], MPNowPlayingInfoPropertyPlaybackRate, nil];
}