//1、調整音頻會話設置，確保應用進入后臺或靜音開關已開啟時音頻仍將繼續播放 //2、鎖屏狀態下顯示媒體信息 //3、鎖屏上的空間可以控制音頻播放#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:@"在后臺播放音頻" 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 //開始寫代碼，調整音頻會話設置，確保即便應用進入后臺或靜音開關已開啟，音頻仍將繼續播放 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:@"停止播放后臺音樂"       forState:UIControlStateNormal];  //No.2  //開始寫代碼，將媒體信息顯示在鎖定屏幕上，并使鎖屏上控件可以控制音頻播放  [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];  //end_code }}//No.3//開始寫代碼，響應遠程控制，使得進入鎖屏狀態后可以控制音樂“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