ios - 向后导航时相机进给卡住 - ios，objective-c

Question

我开发了一个 iOS 应用程序，其中有一个相机可以拍照。我已经使用 AVCaptureSession 来实现相机并且它工作正常。然后我添加了一个 UINavigationController 以转到预览 View (包含拍摄照片的 View )并返回到相机 View 。导航工作没有任何问题，问题是当我回到相机 View 时，相机馈送不再工作，它被卡住了。有人可以帮我解决这个问题吗？我附上了我的代码和 Storyboard的图像。

我用来实现相机馈送的一段代码

@implementation CameraViewController{

    UIView *view_cameraFeed;

    AVCaptureSession *session;

    AVCaptureStillImageOutput *stillImageOutput;

}

- (void)viewDidLoad {

    [super viewDidLoad];

    view_cameraFeed = [[UIView alloc]initWithFrame:CGRectMake(X,Y, WIDTH,HEIGHT)];

    [self.view addSubview:view_cameraFeed];
}

- (void)viewWillAppear:(BOOL)animated{

    session = [[AVCaptureSession alloc] init];

    [session setSessionPreset:AVCaptureSessionPresetPhoto];

    AVCaptureDevice *inputDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

    NSError *error;

    AVCaptureDeviceInput *deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:inputDevice error:&error];

    if ([session canAddInput:deviceInput]) {

        [session addInput:deviceInput];
    }

    AVCaptureVideoPreviewLayer *previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];

    [previewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];

    CALayer *rootLayer = self.view.layer;

    [rootLayer setMasksToBounds:YES];

    CGRect frame = view_cameraFeed.frame;

    [previewLayer setFrame:frame];

    [rootLayer insertSublayer:previewLayer atIndex:0];

    stillImageOutput = [[AVCaptureStillImageOutput alloc] init];

    NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys:AVVideoCodecJPEG, AVVideoCodecKey,nil];

    [stillImageOutput setOutputSettings:outputSettings];

    [session addOutput:stillImageOutput];

    [session startRunning];
}

一段用于导航到预览 View 的代码

 UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];

 UIViewController *CameraPreviewViewController = [storyboard instantiateViewControllerWithIdentifier:@"CameraPreviewViewController"];

[self.navigationController pushViewController:CameraPreviewViewController animated:YES];

用于返回相机源 View 的代码片段

[self.navigationController popViewControllerAnimated:YES];

这是我的 Storyboard

Answer 1

最后我找到了解决这个问题的方法。很抱歉延迟发布答案。

如果我们在 viewWillAppear 中初始化 session 和其余的东西(除了“[session startRunning]”)，当我们导航回 View 时，这些步骤将运行不止一次。这就是它卡住的原因。

我只是将 viewWillAppear 中除“[session startRunning]”之外的所有行移至 viewDidLoad。这样这些行只会运行一次。

这解决了我的问题，这是工作代码。

我用来实现相机馈送的一段代码

@implementation CameraViewController{

    UIView *view_cameraFeed;

    AVCaptureSession *session;

    AVCaptureStillImageOutput *stillImageOutput;

}

- (void)viewDidLoad {

    [super viewDidLoad];

    view_cameraFeed = [[UIView alloc]initWithFrame:CGRectMake(X,Y, WIDTH,HEIGHT)];

    [self.view addSubview:view_cameraFeed];

    session = [[AVCaptureSession alloc] init];

    [session setSessionPreset:AVCaptureSessionPresetPhoto];

    AVCaptureDevice *inputDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

    NSError *error;

    AVCaptureDeviceInput *deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:inputDevice error:&error];

    if ([session canAddInput:deviceInput]) {

        [session addInput:deviceInput];
    }

    AVCaptureVideoPreviewLayer *previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];

    [previewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];

    CALayer *rootLayer = self.view.layer;

    [rootLayer setMasksToBounds:YES];

    CGRect frame = view_cameraFeed.frame;

    [previewLayer setFrame:frame];

    [rootLayer insertSublayer:previewLayer atIndex:0];

    stillImageOutput = [[AVCaptureStillImageOutput alloc] init];

    NSDictionary *outputSettings = [[NSDictionary alloc]     initWithObjectsAndKeys:AVVideoCodecJPEG, AVVideoCodecKey,nil];

    [stillImageOutput setOutputSettings:outputSettings];

    [session addOutput:stillImageOutput];
}

- (void)viewWillAppear:(BOOL)animated{

    [session startRunning];
}

所有其他代码与问题中的相同