如何设置摄像机视图以填充其父视图

Question

我不知道这个问题是关于自动布局还是我做错了什么 我内部有一个UIViewController和一个UIView 我正在使用AVCaptureSession将相机视图放入其中 问题是，当我在摄像机视图中加载视图时，它不会填充该视图，因此左右两侧都有间隙。
我要做的是用相机填充整个UIView 这是我的代码：

...
@IBOutlet weak var camView: UIView!
var previewLayer    : AVCaptureVideoPreviewLayer!

override func viewDidLoad() {
...
previewLayer = AVCaptureVideoPreviewLayer.layerWithSession(session) as! AVCaptureVideoPreviewLayer
        previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
previewLayer.frame = self.camView.layer.bounds
self.camView.layer.addSublayer(previewLayer)
session.startRunning()

Answer 1

您需要在布置子视图后进行设置。在viewDidLayoutSubviews

-(void)viewDidLayoutSubviews
{
    [self setupAVCapture];
}


- (void)setupAVCapture {
    NSError *error = nil;

    AVCaptureSession *session = [AVCaptureSession new];
    if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone)
        [session setSessionPreset:AVCaptureSessionPreset640x480];
    else
        [session setSessionPreset:AVCaptureSessionPresetPhoto];

    // Select a video device, make an input
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    AVCaptureDeviceInput *deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];

    if ([session canAddInput:deviceInput])
        [session addInput:deviceInput];

    AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session];
        [previewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];

    previewLayer.frame = self.camView.bounds;
    [self.camView.layer addSublayer:previewLayer];
    [session startRunning];
}

您可能发生的事情是，viewDidLoad尚未准确设置界限，因为子视图尚未根据其约束进行布局。当您为previewLayer中的viewDidLayoutSubviews设置框架时，它将采用正确的方向。但要小心，你还需要调整旋转预览和不旋转预览，并修改我使用的代码。对不起它不是很快，但这不重要。只需将您的实例化设置移至viewDidLayoutSubviews

即可

因此，对于您的代码，您应该执行以下操作：

override func viewDidLayoutSubviews() {
...
previewLayer = AVCaptureVideoPreviewLayer.layerWithSession(session) as! AVCaptureVideoPreviewLayer
    previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
previewLayer.frame = self.camView.layer.bounds
self.camView.layer.addSublayer(previewLayer)
session.startRunning()

Answer 2

如果您希望图层正确填充UIView，您也可以为它定义约束：

self.camView.layer.addSublayer(previewLayer)
self.camView.layer.layoutManager = CAConstraintLayoutManager.layoutManager();
self.camView.layer.addConstraint(CAConstraint.constraintWithAttribute(CAConstraintAttribute.MinX, relativeTo: self.camView.layer, attribute: CAConstraintAttribute.MinX, scale: 1, offset: 0));
self.camView.layer.addConstraint(CAConstraint.constraintWithAttribute(CAConstraintAttribute.MaxX, relativeTo: self.camView.layer, attribute: CAConstraintAttribute.MaxX, scale: 1, offset: 0));
self.camView.layer.addConstraint(CAConstraint.constraintWithAttribute(CAConstraintAttribute.Width, relativeTo: self.camView.layer, attribute: CAConstraintAttribute.Width, scale: 1, offset: 0));
self.camView.layer.addConstraint(CAConstraint.constraintWithAttribute(CAConstraintAttribute.Height, relativeTo: self.camView.layer, attribute: CAConstraintAttribute.Height, scale: 1, offset: 0));
session.startRunning()

Answer 3

设置priviewLayer约束，如下面的代码所示它将占据整个屏幕。

Leading Space = 0 from mainView
Top Space = 0 from mainView
Bottom Space = 0 from mainView 
Trailing Space = 0 from mainView

希望这对你有所帮助。

Answer 4

这在 Swift 4.2

中对我有用

只需在viewDidLayoutSubviews（）函数中将AVCaptureVideoPreviewLayer的实例框架设置为父视图的框架，如下所示：

public class TestModel : PageModel
{
    [BindProperty]
    public IFormFile UploadPOIF { get; set; }

    [BindProperty, Required, EmailAddress, StringLength(256, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 4)]
    public string Email { get; set; }

    [BindProperty, Required]
    public string FirstName { get; set; }

    [BindProperty, Required]
    public string LastName { get; set; }

    public async Task<IActionResult> OnPostAsync()
    {
        if (ModelState.IsValid)
        {
            await UploadPhoto();
        }
        return Page();
    }
}

Answer 5

如果您使用的是自动布局，请执行以下操作：

1. 将相机视图x = 0并设置为屏幕尺寸
2. 将前导和尾随约束应用于superView

希望这会对你有所帮助。