ios 使用 avcapturesession 切换摄像头

Switch cameras with avcapturesession

提问by Kyle Begeman

Using this tutorial here: http://www.musicalgeometry.com/?p=1297I have created a custom overlay and image capture with AVCaptureSession.

在此处使用本教程：http: //www.musicalgeometry.com/?p= 1297我已经使用AVCaptureSession.

I am attempting to allow the user to switch between the front and back camera. Here is my code in CaptureSessionManagerto switch cameras:

我试图让用户在前后摄像头之间切换。这是我CaptureSessionManager切换相机的代码：

- (void)addVideoInputFrontCamera:(BOOL)front {
    NSArray *devices = [AVCaptureDevice devices];
    AVCaptureDevice *frontCamera;
    AVCaptureDevice *backCamera;

    for (AVCaptureDevice *device in devices) {

        //NSLog(@"Device name: %@", [device localizedName]);

        if ([device hasMediaType:AVMediaTypeVideo]) {

            if ([device position] == AVCaptureDevicePositionBack) {
                //NSLog(@"Device position : back");
                backCamera = device;
            }
            else {
                //NSLog(@"Device position : front");
                frontCamera = device;
            }
        }
    }

    NSError *error = nil;

    if (front) {
        AVCaptureDeviceInput *frontFacingCameraDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:frontCamera error:&error];
        if (!error) {
            if ([[self captureSession] canAddInput:frontFacingCameraDeviceInput]) {
                [[self captureSession] addInput:frontFacingCameraDeviceInput];
            } else {
                NSLog(@"Couldn't add front facing video input");
            }
        }
    } else {
        AVCaptureDeviceInput *backFacingCameraDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:backCamera error:&error];
        if (!error) {
            if ([[self captureSession] canAddInput:backFacingCameraDeviceInput]) {
                [[self captureSession] addInput:backFacingCameraDeviceInput];
            } else {
                NSLog(@"Couldn't add back facing video input");
            }
        }
    }
}

Now in my custom overlay controller I initialize everything like so in viewDidLoad:

现在在我的自定义覆盖控制器中，我像这样初始化所有内容viewDidLoad：

[self setCaptureManager:[[CaptureSessionManager alloc] init]];

[[self captureManager] addVideoInputFrontCamera:NO]; // set to YES for Front Camera, No for Back camera

[[self captureManager] addStillImageOutput];

[[self captureManager] addVideoPreviewLayer];
CGRect layerRect = [[[self view] layer] bounds];
[[[self captureManager] previewLayer] setBounds:layerRect];
[[[self captureManager] previewLayer] setPosition:CGPointMake(CGRectGetMidX(layerRect),CGRectGetMidY(layerRect))];
[[[self view] layer] addSublayer:[[self captureManager] previewLayer]];

[[_captureManager captureSession] startRunning];

The switch camera button is connected to a method called switchCamera. I have tried this:

切换相机按钮连接到一个名为 的方法switchCamera。我试过这个：

- (void)switchCameraView:(id)sender {

    [[self captureManager] addVideoInputFrontCamera:YES]; // set to YES for Front Camera, No for Back camera

}

When calling this, I get the error NSLogfrom the CaptureSessionManagerand I cannot figure out why. In viewDidLoad, if I set the fontCamerato YES, it shows the front camera but cannot switch to back, and vice versa.

调用它时，我NSLog从 中得到错误CaptureSessionManager，我不知道为什么。在 中viewDidLoad，如果我将 设置fontCamera为YES，它会显示前置摄像头但无法切换到后置摄像头，反之亦然。

Any ideas on how to get it to switch properly?

关于如何让它正确切换的任何想法？

回答by NES_4Life

You first need to remove the existing AVCameraInput from the AVCaptureSession and then add a new AVCameraInput to the AVCaptureSession. The following works for me (under ARC):

您首先需要从 AVCaptureSession 中删除现有的 AVCameraInput，然后将新的 AVCameraInput 添加到 AVCaptureSession。以下对我有用（在 ARC 下）：

-(IBAction)switchCameraTapped:(id)sender
{
    //Change camera source
    if(_captureSession)
    {
        //Indicate that some changes will be made to the session
        [_captureSession beginConfiguration];

        //Remove existing input
        AVCaptureInput* currentCameraInput = [_captureSession.inputs objectAtIndex:0];
        [_captureSession removeInput:currentCameraInput];

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

        //Add input to session
        NSError *err = nil;
        AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:newCamera error:&err];
        if(!newVideoInput || err)
        {
            NSLog(@"Error creating capture device input: %@", err.localizedDescription);
        }
        else
        {
            [_captureSession addInput:newVideoInput];
        }

        //Commit all the configuration changes at once
        [_captureSession commitConfiguration];
    }
}

// Find a camera with the specified AVCaptureDevicePosition, returning nil if one is not found
- (AVCaptureDevice *) cameraWithPosition:(AVCaptureDevicePosition) position
{
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice *device in devices) 
    {
        if ([device position] == position) return device;
    }
    return nil;
}

回答by chengsam

Swift 4/5

斯威夫特 4/5

@IBAction func switchCameraTapped(sender: Any) {
    //Change camera source
    if let session = captureSession {
        //Remove existing input
        guard let currentCameraInput: AVCaptureInput = session.inputs.first else {
            return
        }

        //Indicate that some changes will be made to the session
        session.beginConfiguration()
        session.removeInput(currentCameraInput)

        //Get new input
        var newCamera: AVCaptureDevice! = nil
        if let input = currentCameraInput as? AVCaptureDeviceInput {
            if (input.device.position == .back) {
                newCamera = cameraWithPosition(position: .front)
            } else {
                newCamera = cameraWithPosition(position: .back)
            }
        }

        //Add input to session
        var err: NSError?
        var newVideoInput: AVCaptureDeviceInput!
        do {
            newVideoInput = try AVCaptureDeviceInput(device: newCamera)
        } catch let err1 as NSError {
            err = err1
            newVideoInput = nil
        }

        if newVideoInput == nil || err != nil {
            print("Error creating capture device input: \(err?.localizedDescription)")
        } else {
            session.addInput(newVideoInput)
        }

        //Commit all the configuration changes at once
        session.commitConfiguration()
    }
}

// Find a camera with the specified AVCaptureDevicePosition, returning nil if one is not found
func cameraWithPosition(position: AVCaptureDevice.Position) -> AVCaptureDevice? {
    let discoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaType.video, position: .unspecified)
    for device in discoverySession.devices {
        if device.position == position {
            return device
        }
    }

    return nil
}

Swift 3 Edit (Combined with Fran?ois-Julien Alcaraz answer):

Swift 3 Edit（结合 Fran?ois-Julien Alcaraz 的回答）：

@IBAction func switchCameraTapped(sender: Any) {
    //Change camera source
    if let session = captureSession {
        //Indicate that some changes will be made to the session
        session.beginConfiguration()

        //Remove existing input
        guard let currentCameraInput: AVCaptureInput = session.inputs.first as? AVCaptureInput else {
            return
        }

        session.removeInput(currentCameraInput)

        //Get new input
        var newCamera: AVCaptureDevice! = nil
        if let input = currentCameraInput as? AVCaptureDeviceInput {
            if (input.device.position == .back) {
                newCamera = cameraWithPosition(position: .front)
            } else {
                newCamera = cameraWithPosition(position: .back)
            }
        }

        //Add input to session
        var err: NSError?
        var newVideoInput: AVCaptureDeviceInput!
        do {
            newVideoInput = try AVCaptureDeviceInput(device: newCamera)
        } catch let err1 as NSError {
            err = err1
            newVideoInput = nil
        }

        if newVideoInput == nil || err != nil {
            print("Error creating capture device input: \(err?.localizedDescription)")
        } else {
            session.addInput(newVideoInput)
        }

        //Commit all the configuration changes at once
        session.commitConfiguration()
    }
}

// Find a camera with the specified AVCaptureDevicePosition, returning nil if one is not found
func cameraWithPosition(position: AVCaptureDevicePosition) -> AVCaptureDevice? {
    if let discoverySession = AVCaptureDeviceDiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaTypeVideo, position: .unspecified) {
        for device in discoverySession.devices {
            if device.position == position {
                return device
            }
        }
    }

    return nil
}

Swift version to @NES_4Life's answer:

@NES_4Life 答案的 Swift 版本：

@IBAction func switchCameraTapped(sender: AnyObject) {
    //Change camera source
    if let session = captureSession {
        //Indicate that some changes will be made to the session
        session.beginConfiguration()

        //Remove existing input
        let currentCameraInput:AVCaptureInput = session.inputs.first as! AVCaptureInput
        session.removeInput(currentCameraInput)

        //Get new input
        var newCamera:AVCaptureDevice! = nil
        if let input = currentCameraInput as? AVCaptureDeviceInput {
            if (input.device.position == .Back)
            {
                newCamera = cameraWithPosition(.Front)
            }
            else
            {
                newCamera = cameraWithPosition(.Back)
            }
        }

        //Add input to session
        var err: NSError?
        var newVideoInput: AVCaptureDeviceInput!
        do {
            newVideoInput = try AVCaptureDeviceInput(device: newCamera)
        } catch let err1 as NSError {
            err = err1
            newVideoInput = nil
        }

        if(newVideoInput == nil || err != nil)
        {
            print("Error creating capture device input: \(err!.localizedDescription)")
        }
        else
        {
            session.addInput(newVideoInput)
        }

        //Commit all the configuration changes at once
        session.commitConfiguration()
    }
}

// Find a camera with the specified AVCaptureDevicePosition, returning nil if one is not found
func cameraWithPosition(position: AVCaptureDevicePosition) -> AVCaptureDevice?
{
    let devices = AVCaptureDevice.devicesWithMediaType(AVMediaTypeVideo)
    for device in devices {
        let device = device as! AVCaptureDevice
        if device.position == position {
            return device
        }
    }

    return nil
}

回答by Fantini

Based on previous answers I made my own version with some validations and one specific change, the current camera input might not be the first object of the capture session's inputs, so I changed this:

根据之前的答案，我制作了自己的版本并进行了一些验证和一个特定的更改，当前的相机输入可能不是捕获会话输入的第一个对象，因此我更改了以下内容：

//Remove existing input
AVCaptureInput* currentCameraInput = [self.captureSession.inputs objectAtIndex:0];
[self.captureSession removeInput:currentCameraInput];

To this (removing all video type inputs):

为此（删除所有视频类型输入）：

for (AVCaptureDeviceInput *input in self.captureSession.inputs) {
    if ([input.device hasMediaType:AVMediaTypeVideo]) {
        [self.captureSession removeInput:input];
        break;
    }
}

Here's the entire code:

这是整个代码：

if (!self.captureSession) return;

[self.captureSession beginConfiguration];

AVCaptureDeviceInput *currentCameraInput;

// Remove current (video) input
for (AVCaptureDeviceInput *input in self.captureSession.inputs) {
    if ([input.device hasMediaType:AVMediaTypeVideo]) {
        [self.captureSession removeInput:input];

        currentCameraInput = input;
        break;
    }
}

if (!currentCameraInput) return;

// Switch device position
AVCaptureDevicePosition captureDevicePosition = AVCaptureDevicePositionUnspecified;
if (currentCameraInput.device.position == AVCaptureDevicePositionBack) {
    captureDevicePosition = AVCaptureDevicePositionFront;
} else {
    captureDevicePosition = AVCaptureDevicePositionBack;
}

// Select new camera
AVCaptureDevice *newCamera;
NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];

for (AVCaptureDevice *captureDevice in devices) {
    if (captureDevice.position == captureDevicePosition) {
        newCamera = captureDevice;
    }
}

if (!newCamera) return;

// Add new camera input
NSError *error;
AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:newCamera error:&error];
if (!error && [self.captureSession canAddInput:newVideoInput]) {
    [self.captureSession addInput:newVideoInput];
}

[self.captureSession commitConfiguration];

回答by Bohdan Savych

Swift 3

斯威夫特 3

func switchCamera() {
        session?.beginConfiguration()
        let currentInput = session?.inputs.first as? AVCaptureDeviceInput
        session?.removeInput(currentInput)

        let newCameraDevice = currentInput?.device.position == .back ? getCamera(with: .front) : getCamera(with: .back)
        let newVideoInput = try? AVCaptureDeviceInput(device: newCameraDevice)
        session?.addInput(newVideoInput)
        session?.commitConfiguration()
    }

// MARK: - Private
extension CameraService {
    func getCamera(with position: AVCaptureDevicePosition) -> AVCaptureDevice? {
        guard let devices = AVCaptureDevice.devices(withMediaType: AVMediaTypeVideo) as? [AVCaptureDevice] else {
            return nil
        }

        return devices.filter {
            
func switchCameraTapped() {
    //Change camera source
    //Indicate that some changes will be made to the session
    session.beginConfiguration()

    //Remove existing input
    guard let currentCameraInput: AVCaptureInput = session.inputs.first else {
        return
    }


    //Get new input
    var newCamera: AVCaptureDevice! = nil
    if let input = currentCameraInput as? AVCaptureDeviceInput {
        if (input.device.position == .back) {
            newCamera = cameraWithPosition(position: .front)
        } else {
            newCamera = cameraWithPosition(position: .back)
        }
    }

    //Add input to session
    var err: NSError?
    var newVideoInput: AVCaptureDeviceInput!
    do {
        newVideoInput = try AVCaptureDeviceInput(device: newCamera)
    } catch let err1 as NSError {
        err = err1
        newVideoInput = nil
    }

    if let inputs = session.inputs as? [AVCaptureDeviceInput] {
        for input in inputs {
            session.removeInput(input)
        }
    }


    if newVideoInput == nil || err != nil {
        print("Error creating capture device input: \(err?.localizedDescription)")
    } else {
        session.addInput(newVideoInput)
    }

    //Commit all the configuration changes at once
    session.commitConfiguration()
}

// Find a camera with the specified AVCaptureDevicePosition, returning nil if one is not found
func cameraWithPosition(position: AVCaptureDevice.Position) -> AVCaptureDevice? {
    let discoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaType.video, position: .unspecified)
    for device in discoverySession.devices {
        if device.position == position {
            return device
        }
    }

    return nil
}
.position == position
        }.first
    }
}

Swift 4

斯威夫特 4

You can check full implementation in this gist

您可以在此要点中检查完整实现

回答by william

Here is an updated version of chengsam's code that includes the fix for 'Multiple audio/video AVCaptureInputs are not currently supported'.

这是 chengsam 代码的更新版本，其中包括“当前不支持多个音频/视频 AVCaptureInputs”的修复程序。

    // Find a camera with the specified AVCaptureDevicePosition, returning nil if one is not found
func cameraWithPosition(_ position: AVCaptureDevicePosition) -> AVCaptureDevice?
{
    if let deviceDescoverySession = AVCaptureDeviceDiscoverySession.init(deviceTypes: [AVCaptureDeviceType.builtInWideAngleCamera],
                                                          mediaType: AVMediaTypeVideo,
                                                          position: AVCaptureDevicePosition.unspecified) {

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

    return nil
}

回答by hefgi

Swift 3 version of cameraWithPosition without deprecated warning :

没有弃用警告的 Swift 3 版本的 cameraWithPosition ：

##代码##

If you want, you can also get the new devicesTypes from iPhone 7+ (dual camera) by changing the deviceTypes array.

如果需要，您还可以通过更改 deviceTypes 数组从 iPhone 7+（双摄像头）获取新的 devicesTypes。

Here's a good read : https://forums.developer.apple.com/thread/63347

这是一个很好的阅读：https: //forums.developer.apple.com/thread/63347