在Apple Watch上使用 AVAudioRecorder and AVAudioPlayer

WatchOS4 引入了AVFoundation这款强大的音视频框架。
如果你在Watch模拟器时使用AVAudioRecorder和AVAudioPlayer，你会发觉很好用。代码如下

- (void)awakeWithContext:(id)context {
    [super awakeWithContext:context];

    // Configure interface objects here.
    NSString *cachePath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject;
    
    // 拼接文件名
    NSString *filePath = [cachePath stringByAppendingPathComponent:@"f1x.m4a"];

    NSData *data = [NSData dataWithContentsOfFile:filePath];
    NSLog(@"data lenght: %lu",(unsigned long)data.length);
    NSURL *fileURL = [NSURL fileURLWithPath:filePath];
    NSDictionary *settings = @{AVFormatIDKey:@(kAudioFormatMPEG4AAC),
                               AVSampleRateKey:@(12000),
                               AVNumberOfChannelsKey:@(1),
                               AVEncoderAudioQualityKey:@(AVAudioQualityHigh)
                               };
    NSError *error = nil;

    _recorder = [[AVAudioRecorder alloc] initWithURL:fileURL settings:settings error:&error];
    NSLog(@"create record error: %@",error);
    _recorder.delegate = self;
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(sessionactive) name:@"xxx" object:nil];
    
}

- (IBAction)recordAction {
    [_recorder record];
}
- (IBAction)playAction {
    [self.player play];
    
}
- (IBAction)stopAction {
    [_recorder stop];
}
- (AVAudioPlayer *)player {
    
        NSError *error = nil;
    NSString *cachePath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject;
    
    // 拼接文件名
    NSString *filePath = [cachePath stringByAppendingPathComponent:@"f1x.m4a"];
    NSData *data = [NSData dataWithContentsOfFile:filePath];
    NSLog(@"data length: %d",data.length);
        _player = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL URLWithString:filePath] error:&error];
    NSLog(@"create error: %@",error);
        [_player prepareToPlay];
        _player.volume = 0.9;
        _player.delegate = self;
        
    
    return _player;
}

但是当你把这段代码运行到真机的时候，你会发现以下情况
1.打印的文件长度是固定的
2.player播放不了，没有任何声音

这是因为你没有在iphone端(不是WatchKit)的info.plist添加隐私政策“Privacy - Microphone Usage Description”
加完就好了