//1、調整音訊會話設定，確保應用進入後臺或靜音開關已開啟時音訊仍將繼續播放 2、鎖屏狀態下顯示媒體資訊 3、鎖屏上的空間可以控制音訊播放

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

@interface ViewController ()

@property (nonatomic, strong) AVAudioPlayer *audioPlayer;
@property (weak, nonatomic)  UIButton
 
 *playButton;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    UIButton * playButton = [UIButton buttonWithType:UIButtonTypeSystem];
    playButton.frame = CGRectMake(0, 0, 200, 40);
    playButton.center = self.view.center;
    [playButton setTitle:@"在後臺播放音訊" forState:UIControlStateNormal];
    [playButton addTarget:self
 
 action:@selector(playMusicInBackground:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:playButton];

    NSError *playerInitError = nil;

    NSString *audioPath =
    [[NSBundle mainBundle] pathForResource:@"background_audio"
                                    ofType:@"mp3"
 
];

    NSURL *audioURL = [NSURL fileURLWithPath:audioPath];

    self.audioPlayer = [[AVAudioPlayer alloc]
                        initWithContentsOfURL:audioURL
                        error:&playerInitError];

    AVAudioSession *session = [AVAudioSession sharedInstance];

    NSError *activeError = nil;
    if (![session setActive:YES error:&activeError]) {
        NSLog(@"Failed to set active audio session!");
    }

    //No.1
    //開始寫程式碼，調整音訊會話設定，確保即便應用進入後臺或靜音開關已開啟，音訊仍將繼續播放

    NSError *categoryError = nil;
    [session setCategory:AVAudioSessionCategoryPlayback error:&categoryError];


    //end_code


}
- (void)playMusicInBackground:(id)sender {

    if ([self.audioPlayer isPlaying]) {
        [self.audioPlayer stop];

        [self.playButton setTitle:@"正在播放音樂"
                         forState:UIControlStateNormal];

    } else {
        UIImage *lockImage = [UIImage imageNamed:@"belongToMe.jpg"];

        MPMediaItemArtwork *artwork =
        [[MPMediaItemArtwork alloc] initWithImage:lockImage];

        NSDictionary *mediaDict =
        @{
          MPMediaItemPropertyTitle: @"BackgroundTask Audio",
          MPMediaItemPropertyMediaType: @(MPMediaTypeAnyAudio),
          MPMediaItemPropertyPlaybackDuration:
              @(self.audioPlayer.duration),
          MPNowPlayingInfoPropertyPlaybackRate: @1.0,
          MPNowPlayingInfoPropertyElapsedPlaybackTime:
              @(self.audioPlayer.currentTime),
          MPMediaItemPropertyAlbumArtist: @"Some User",
          MPMediaItemPropertyArtist: @"Some User",
          MPMediaItemPropertyArtwork: artwork };

        [self.audioPlayer play];

        [self.playButton setTitle:@"停止播放後臺音樂"
                         forState:UIControlStateNormal];

        //No.2
        //開始寫程式碼，將媒體資訊顯示在鎖定螢幕上，並使鎖屏上控制元件可以控制音訊播放


        [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];


        //end_code
    }
}

//No.3
//開始寫程式碼，響應遠端控制，使得進入鎖屏狀態後可以控制音樂“播放”和“暫停”


- (void) remoteControlReceivedWithEvent: (UIEvent *) receivedEvent {

    if (receivedEvent.type == UIEventTypeRemoteControl) {
        switch (receivedEvent.subtype) {

            case UIEventSubtypeRemoteControlPlay:
                [self.audioPlayer play];
                break;

            case UIEventSubtypeRemoteControlPause:
                [self.audioPlayer pause];
                break;

            default:
                NSLog(@"沒有處理過這個事件------receivedEvent.subtype==%ld",(long)receivedEvent.subtype);
                break;
        }
    }
}


//end_code

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}

@end