iOS - 代码仅在插入断点时有效

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我开始弄清楚这一点。AVAudioRecorder会话被激活，我得到几秒钟的麦克风电平读数。然后异步视频代码完成，显示摄像机视图，我停止获取读数。视频似乎正在杀死音频会话。

奇怪的是，该代码适用于iOS 7，而不适用于iOS 6。任何想法如何解决这个问题。这是 iOS 6 的限制吗？

我通过麦克风获得声级，只有当我在设置录音机对象的代码上放置断点时，我才能获得它们。如果我在那个点上没有暂停几秒钟就跑了，它就无法获得关卡。这段代码在viewDidLoad中，我可以将断点放在前3行之一上：

_recorder = [[AVAudioRecorder alloc] initWithURL:url settings:settings error:&error];
[_recorder prepareToRecord];
_recorder.meteringEnabled = YES;
    _levelTimer = [NSTimer scheduledTimerWithTimeInterval: 0.03 target: self selector: @selector(levelTimerCallback) userInfo: nil repeats: YES];

我在 levelTimerCallback 方法中获取我的级别。

这段代码进入视图DidAppear：

    NSError *error;
if (_recorder) {
    [_recorder record];
} else
    NSLog(@"Error: %@", [error description]);

编辑：

级别定时器回调代码：

    [_recorder updateMeters];
const double ALPHA = 0.05;
double peakPowerForChannel = pow(10, (0.05 * [_recorder peakPowerForChannel:0]));
_lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * _lowPassResults;
NSLog(@"Average input: %f Peak input: %f", [_recorder averagePowerForChannel:0], [_recorder peakPowerForChannel:0]);

异步代码在记录器代码上方运行：

            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            [[[self captureManager] session] startRunning];
        });

相机代码：

    if ([self captureManager] == nil) {
    AVCamCaptureManager *manager = [[AVCamCaptureManager alloc] init];
    [self setCaptureManager:manager];
    [[self captureManager] setDelegate:self];
    if ([[self captureManager] setupSession]) {
        // Create video preview layer and add it to the UI
        AVCaptureVideoPreviewLayer *newCaptureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:[[self captureManager] session]];
        UIView *view = [self videoPreviewView];
        CALayer *viewLayer = [view layer];
        [viewLayer setMasksToBounds:YES];
        CGRect bounds = [view bounds];
        [newCaptureVideoPreviewLayer setFrame:bounds];
        if ([[newCaptureVideoPreviewLayer connection] isVideoOrientationSupported]) {
            [[newCaptureVideoPreviewLayer connection] setVideoOrientation:AVCaptureVideoOrientationPortrait];
        }
        [newCaptureVideoPreviewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
        [viewLayer insertSublayer:newCaptureVideoPreviewLayer below:[[viewLayer sublayers] objectAtIndex:0]];
        [self setCaptureVideoPreviewLayer:newCaptureVideoPreviewLayer];
        // Start the session. This is done asychronously since -startRunning doesn't return until the session is running.
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            [[[self captureManager] session] startRunning];
        });

        [self addObserver:self forKeyPath:@"captureManager.videoInput.device.focusMode" options:NSKeyValueObservingOptionNew context:AVCamFocusModeObserverContext];
        // Add a single tap gesture to focus on the point tapped, then lock focus
        UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapToAutoFocus:)];
        [singleTap setDelegate:self];
        [singleTap setNumberOfTapsRequired:1];
        [view addGestureRecognizer:singleTap];
        // Add a double tap gesture to reset the focus mode to continuous auto focus
        UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapToContinouslyAutoFocus:)];
        [doubleTap setDelegate:self];
        [doubleTap setNumberOfTapsRequired:2];
        [singleTap requireGestureRecognizerToFail:doubleTap];
        [view addGestureRecognizer:doubleTap];
    }
}
NSURL *url = [NSURL fileURLWithPath:@"/dev/null"];
NSDictionary *settings = [NSDictionary dictionaryWithObjectsAndKeys:
                          [NSNumber numberWithFloat: 44100.0],                 AVSampleRateKey,
                          [NSNumber numberWithInt: kAudioFormatAppleLossless], AVFormatIDKey,
                          [NSNumber numberWithInt: 1],                         AVNumberOfChannelsKey,
                          [NSNumber numberWithInt: AVAudioQualityMax],         AVEncoderAudioQualityKey,
                          nil];
AVAudioSession *audioSession = [AVAudioSession sharedInstance];
[audioSession setActive: YES error: nil];
[[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryRecord error: nil];
NSError *error;
_recorder = [[AVAudioRecorder alloc] initWithURL:url settings:settings error:&error];

Answer 1

我相信

你应该在viewDidAppear结束时调用_levelTimer = [NSTimer scheduledTimerWithTimeInterval: 0.03 target: self selector: @selector(levelTimerCallback) userInfo: nil repeats: YES]; ，并将其取消并在viewDidDisappear中使其无效。当您viewDidAppear中有其他代码时，从viewDidLoad触发计时器没有意义。您可能还想检查使用主线程而不是后台线程进行[[[self captureManager] session] startRunning];。