因为自己的项目领域，基本没有涉及到视频，音频等内容，所以逐渐的很陌生，脑袋也记不太多相关，所以今天又重新温习了一遍。好记性不如烂笔头嘛~hold on。

1.音效的播放

1.获得音效文件的路径

NSURL *url = [[NSBundle mainBundle] URLForResource:@"文件名称" withExtension:nil];

2.加载音效文件，得到对应的音效ID

SystemSoundID soundID = 0;
AudioServicesCreateSystemSoundID((__bridge CFURLRef)(url), &soundID);

3.播放音效

AudioServicesPlaySystemSound(soundID);

2.录音

1. 录音步骤
   1.导入AVFoundation框架

    #import <AVFoundation/AVFoundation.h>
   

2.使用类AVAudioRecorder进行录音

1. 创建录音文件存放路径
   一般是沙盒路径

     NSString *path = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"text.caf"];
     NSURL *url = [NSURL URLWithString:path];
   

2. 设置录音附加设置项(#import <AVFoundation/AVAudioSettings.h>)

   NSMutableDictionary *recordSettings = [[NSMutableDictionary alloc] init];
   

设置编码格式

 [recordSettings setValue :[NSNumber numberWithInt:kAudioFormatLinearPCM] forKey: AVFormatIDKey];

采样率

 [recordSettings setValue :[NSNumber numberWithFloat:11025.0] forKey: AVSampleRateKey];44100.0

通道数

[recordSettings setValue :[NSNumber numberWithInt:2] forKey: AVNumberOfChannelsKey];

音频质量,采样质量

    [recordSettings setValue:[NSNumber numberWithInt:AVAudioQualityMin] forKey:AVEncoderAudioQualityKey];

3. 根据路径以及设置项, 创建录音对象

     _audioRecorder = [[AVAudioRecorder alloc] initWithURL:url settings:recordSettings error:nil];
   

4. 准备录音

   [self.audioRecorder prepareToRecord];
   

5. 开始录音

   [self.audioRecorder record];
   

6. 停止录音

   [self.audioRecorder stop];
   

3.音乐播放+ 后台+锁屏显示

1. 勾选后台模式 音频播放

2. 激活音频播放会话

1. 获取音频会话
   AVAudioSession *session = [AVAudioSession sharedInstance];
2. 设置会话分类
   [session setCategory:AVAudioSessionCategoryPlayback error:nil];
3. 激活会话
   [session setActive:YES error:nil];

3.设置定时器

__weak typeof(self) weakSelf = self;

//设置无限循环 每0.1秒调用一次block  相当于定时器了吧
_playerTimeObserver = [self.player addPeriodicTimeObserverForInterval:CMTimeMake(0.1*30, 30) queue:dispatch_get_main_queue() usingBlock:^(CMTime time) {
    //获取当前时间
    CGFloat currentTime = CMTimeGetSeconds(time);
    //获取所有时间
    CMTime total = weakSelf.player.currentItem.duration;
    CGFloat totalTime = CMTimeGetSeconds(total);
  //在定时器里面 进行歌词刷新 
   }
   //监听锁屏状态 lock = 1  则为锁屏状态
   uint64_t locked;
   __block int token = 0;
   notify_register_dispatch("com.apple.springboard.lockstate", &token, dispatch_get_main_queue(), ^(int token) {
       NSLog(@"锁屏了");
   });
   
   notify_get_state(token, &locked);
   
   //监听屏幕点亮状态 screenLight = 1 则为变暗关闭状态
   uint64_t screenLight;
   __block int lightToken = 0;
   
   notify_register_dispatch("com.apple.springboard.hasBlankedScreen", &lightToken, dispatch_get_main_queue(), ^(int token) {
       
   });
   
   notify_get_state(lightToken, &screenLight);
   BOOL isShowLyricsPoster = NO;
   if (screenLight == 0 && locked == 1) {
       // 点亮且 锁屏时候
   }else if (screenLight) {
       //暗屏时候
       return;
   }

4配置锁屏信息
定时器加载这些信息

     NSMutableDictionary *songDict = [[NSMutableDictionary alloc] init];
[songDict setObject:@"歌名" forKey:MPMediaItemPropertyTitle];
[songDict setObject:@"歌手" forKey:MPMediaItemPropertyArtist];
[songDict setObject:@"专辑名" forKey:MPMediaItemPropertyAlbumTitle];
//设置歌曲时长
[songDict setObject:[NSNumber numberWithDouble:totalTime] forKey:MPMediaItemPropertyPlaybackDuration];
//设置已经播放时长
[songDict setObject:[NSNumber numberWithDouble:currentTime] forKey:MPNowPlayingInfoPropertyElapsedPlaybackTime];
//设置播放速率
[songDict setObject:[NSNumber numberWithInteger:rate] forKey:MPNowPlayingInfoPropertyPlaybackRate]; 

//设置显示海报图片
//这个可以是截屏

    [songDict setObject:[[MPMediaItemArtwork      alloc]initWithImage:Image]     forKey:MPMediaItemPropertyArtwork];

//获取锁屏信息中心  以及设置锁屏信息
    [[MPNowPlayingInfoCenter defaultCenter]     setNowPlayingInfo:songDict];

5设置锁屏按钮等

//MPFeedbackCommand 对象反映了当前app所播放的反馈状态 MPRemoteCommandCenter 对象提供了feedback对象用于对媒体文件进行喜欢 不喜欢 标记的操作 类似于 网易云音乐锁屏时的效果

MPRemoteCommandCenter *commandCenter = 
[MPRemoteCommandCenter sharedCommandCenter];

MPFeedbackCommand *linkCommand = commandCenter.likeCommand;
linkCommand.enabled = YES;
linkCommand.localizedTitle = @"喜欢";
[linkCommand addTargetWithHandler:^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {
    NSLog(@"喜欢");
    return MPRemoteCommandHandlerStatusSuccess;
}];

MPFeedbackCommand *disLikeCommand = commandCenter.dislikeCommand;

disLikeCommand.enabled = YES;
disLikeCommand.localizedTitle = @"not like";

[disLikeCommand addTargetWithHandler:^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {
    NSLog(@"不喜欢");
    return MPRemoteCommandHandlerStatusSuccess;
}];
__weak typeof(self) weakSelf = self;
[commandCenter.pauseCommand addTargetWithHandler:^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {
    [weakSelf.player pause];
    return MPRemoteCommandHandlerStatusSuccess;
}];

[commandCenter.playCommand addTargetWithHandler:^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {
    [weakSelf.player play];
    return MPRemoteCommandHandlerStatusSuccess;
}];