使用AVCaptureSession切换前/后摄像头

Question

我正在关注这个问题的唯一答案 -

用avcapturesession切换相机

但是cameraWithPosition似乎不起作用.已过时？

//Get new input
    AVCaptureDevice *newCamera = nil;
    if(((AVCaptureDeviceInput*)currentCameraInput).device.position == AVCaptureDevicePositionBack)
    {
        newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
    }
    else
    {
        newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
    }

Answer 1

你需要做的是重新配置你的 AVCaptureSession

这是我正在使用的:

// note that `AVCaptureSession * session`
//
if(session)
{
    [session beginConfiguration];

    AVCaptureInput *currentCameraInput = [session.inputs objectAtIndex:0];

    [session removeInput:currentCameraInput];

    AVCaptureDevice *newCamera = nil;

    if(((AVCaptureDeviceInput*)currentCameraInput).device.position == AVCaptureDevicePositionBack)
    {
        newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
    }
    else
    {
        newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
    }

    NSError *err = nil;

    AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:newCamera error:&err];

    if(!newVideoInput || err)
    {
        NSLog(@"Error creating capture device input: %@", err.localizedDescription);
    }
    else
    {
        [session addInput:newVideoInput];
    }

    [session commitConfiguration];
}

// make sure you have this method in your class
//
- (AVCaptureDevice *)cameraWithPosition:(AVCaptureDevicePosition)position
{
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];

    for (AVCaptureDevice *device in devices)
    {
        if ([device position] == position)
            return device;
    }
    return nil;
}

Answer 2

在Swift 3.0中

/// Swap camera and reconfigures camera session with new input
fileprivate func swapCamera() {

    // Get current input
    guard let input = cameraSession.inputs[0] as? AVCaptureDeviceInput else { return }

    // Begin new session configuration and defer commit
    cameraSession.beginConfiguration()
    defer { cameraSession.commitConfiguration() }

    // Create new capture device
    var newDevice: AVCaptureDevice?
    if input.device.position == .back {
        newDevice = captureDevice(with: .front)
    } else {
        newDevice = captureDevice(with: .back)
    }

    // Create new capture input
    var deviceInput: AVCaptureDeviceInput!
    do {
        deviceInput = try AVCaptureDeviceInput(device: newDevice)
    } catch let error {
        print(error.localizedDescription)
        return
    }

    // Swap capture device inputs
    cameraSession.removeInput(input)
    cameraSession.addInput(deviceInput)
}

/// Create new capture device with requested position
fileprivate func captureDevice(with position: AVCaptureDevicePosition) -> AVCaptureDevice? {

    let devices = AVCaptureDeviceDiscoverySession(deviceTypes: [ .builtInWideAngleCamera, .builtInMicrophone, .builtInDualCamera, .builtInTelephotoCamera ], mediaType: AVMediaTypeVideo, position: .unspecified).devices

    if let devices = devices {
        for device in devices {
            if device.position == position {
                return device
            }
        }
    }

    return nil
}

Answer 3

Swift 4.2 的代码更新

/// Swap camera and reconfigures camera session with new input
fileprivate func swapCamera() {

    // Get current input
    guard let input = captureSession.inputs[0] as? AVCaptureDeviceInput else { return }

    // Begin new session configuration and defer commit
    captureSession.beginConfiguration()
    defer { captureSession.commitConfiguration() }

    // Create new capture device
    var newDevice: AVCaptureDevice?
    if input.device.position == .back {
        newDevice = captureDevice(with: .front)
    } else {
        newDevice = captureDevice(with: .back)
    }

    // Create new capture input
    var deviceInput: AVCaptureDeviceInput!
    do {
        deviceInput = try AVCaptureDeviceInput(device: newDevice!)
    } catch let error {
        print(error.localizedDescription)
        return
    }

    // Swap capture device inputs
    captureSession.removeInput(input)
    captureSession.addInput(deviceInput)
}

/// Create new capture device with requested position
fileprivate func captureDevice(with position: AVCaptureDevice.Position) -> AVCaptureDevice? {

    let devices = AVCaptureDevice.DiscoverySession(deviceTypes: [ .builtInWideAngleCamera, .builtInMicrophone, .builtInDualCamera, .builtInTelephotoCamera ], mediaType: AVMediaType.video, position: .unspecified).devices

    //if let devices = devices {
        for device in devices {
            if device.position == position {
                return device
            }
        }
    //}

    return nil
}