Background: I'm running a swift 2 application with the following two options.
Option A: The user can enter a number to sign in. In this case, his/her picture is shown in a UIImageView.
Option B: The user can use an NFC tag to sign in. In this case, the UIImageView is replaced with a camera layer that shows live camera stream and uses CIContext to capture an image on a button press.
Problem: The issue I'm facing is that sometimes, when I choose option A (not using the camera layer), the app crashes. Since I'm unable to reproduce the crash deterministically, I have hit a dead end to understand why the app is crashing.
EDIT: The camera layer is used in both options but is hidden in option A.
Crashlytics generates the following crash log:
0 libswiftCore.dylib specialized _fatalErrorMessage(StaticString, StaticString, StaticString, UInt) -> () + 44
1 CameraLayerView.swift line 20 CameraLayerView.init(coder : NSCoder) -> CameraLayerView?
2 CameraLayerView.swift line 0 @objc CameraLayerView.init(coder : NSCoder) -> CameraLayerView?
3 UIKit -[UIClassSwapper initWithCoder:] + 248
32 UIKit UIApplicationMain + 208
33 AppDelegate.swift line 17 main
34 libdispatch.dylib (Missing)
I've checked line#20 in CameraLayerView but it is just an initialization statement
private let ciContext = CIContext(EAGLContext: EAGLContext(API: .OpenGLES2))
Mentioned below is the CameraLayerView file. Any help would be appreciated
var captureSession = AVCaptureSession()
var sessionOutput = AVCaptureVideoDataOutput()
var previewLayer = AVCaptureVideoPreviewLayer()
private var pixelBuffer : CVImageBuffer!
private var attachments : CFDictionary!
private var ciImage : CIImage!
private let ciContext = CIContext(EAGLContext: EAGLContext(API: .OpenGLES2))
private var imageOptions : [String : AnyObject]!
var faceFound = false
var image : UIImage!
override func layoutSubviews() {
previewLayer.position = CGPoint(x: self.frame.width/2, y: self.frame.height/2)
previewLayer.bounds = self.frame
self.layer.borderWidth = 2.0
self.layer.borderColor = UIColor.redColor().CGColor
}
func loadCamera() {
let camera = AVCaptureDevice.devicesWithMediaType(AVMediaTypeVideo)
for device in camera {
if device.position == .Front {
do{
for input in captureSession.inputs {
captureSession.removeInput(input as! AVCaptureInput)
}
for output in captureSession.outputs {
captureSession.removeOutput(output as! AVCaptureOutput)
}
previewLayer.removeFromSuperlayer()
previewLayer.session = nil
let input = try AVCaptureDeviceInput(device: device as! AVCaptureDevice)
if captureSession.canAddInput(input) {
captureSession.addInput(input)
sessionOutput.videoSettings = [String(kCVPixelBufferPixelFormatTypeKey) : Int(kCVPixelFormatType_32BGRA)]
sessionOutput.setSampleBufferDelegate(self, queue: dispatch_get_global_queue(Int(QOS_CLASS_BACKGROUND.rawValue), 0))
sessionOutput.alwaysDiscardsLateVideoFrames = true
if captureSession.canAddOutput(sessionOutput) {
captureSession.addOutput(sessionOutput)
captureSession.sessionPreset = AVCaptureSessionPresetPhoto
captureSession.startRunning()
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
switch UIDevice.currentDevice().orientation.rawValue {
case 1:
previewLayer.connection.videoOrientation = AVCaptureVideoOrientation.Portrait
break
case 2:
previewLayer.connection.videoOrientation = AVCaptureVideoOrientation.PortraitUpsideDown
break
case 3:
previewLayer.connection.videoOrientation = AVCaptureVideoOrientation.LandscapeRight
break
case 4:
previewLayer.connection.videoOrientation = AVCaptureVideoOrientation.LandscapeLeft
break
default:
break
}
self.layer.addSublayer(previewLayer)
}
}
} catch {
print("Error")
}
}
}
}
func takePicture() -> UIImage {
self.previewLayer.removeFromSuperlayer()
self.captureSession.stopRunning()
return image
}
func captureOutput(captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, fromConnection connection: AVCaptureConnection!) {
pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
attachments = CMCopyDictionaryOfAttachments(kCFAllocatorDefault, sampleBuffer, kCMAttachmentMode_ShouldPropagate)
ciImage = CIImage(CVPixelBuffer: pixelBuffer!, options: attachments as? [String : AnyObject])
if UIDevice.currentDevice().orientation == .PortraitUpsideDown {
imageOptions = [CIDetectorImageOrientation : 8]
} else if UIDevice.currentDevice().orientation == .LandscapeLeft {
imageOptions = [CIDetectorImageOrientation : 3]
} else if UIDevice.currentDevice().orientation == .LandscapeRight {
imageOptions = [CIDetectorImageOrientation : 1]
} else {
imageOptions = [CIDetectorImageOrientation : 6]
}
let faceDetector = CIDetector(ofType: CIDetectorTypeFace, context: ciContext, options: [CIDetectorAccuracy: CIDetectorAccuracyHigh])
let features = faceDetector.featuresInImage(ciImage, options: imageOptions)
if features.count == 0 {
if faceFound == true {
faceFound = false
dispatch_async(dispatch_get_main_queue()) {
self.layer.borderColor = UIColor.redColor().CGColor
}
}
} else {
if UIDevice.currentDevice().orientation == .PortraitUpsideDown {
image = UIImage(CGImage: ciContext.createCGImage(ciImage, fromRect: ciImage.extent), scale: 1.0, orientation: UIImageOrientation.Left)
} else if UIDevice.currentDevice().orientation == .LandscapeLeft {
image = UIImage(CGImage: ciContext.createCGImage(ciImage, fromRect: ciImage.extent), scale: 1.0, orientation: UIImageOrientation.Down)
} else if UIDevice.currentDevice().orientation == .LandscapeRight {
image = UIImage(CGImage: ciContext.createCGImage(ciImage, fromRect: ciImage.extent), scale: 1.0, orientation: UIImageOrientation.Up)
} else {
image = UIImage(CGImage: ciContext.createCGImage(ciImage, fromRect: ciImage.extent), scale: 1.0, orientation: UIImageOrientation.Right)
}
if faceFound == false {
faceFound = true
for feature in features {
if feature.isKindOfClass(CIFaceFeature) {
dispatch_async(dispatch_get_main_queue()) {
self.layer.borderColor = UIColor.greenColor().CGColor
}
}
}
}
}
}
答案 0 :(得分：0)
我测试了一个理论并且它起作用了。由于ciContext正在使用视图初始化进行初始化，因此看起来应用程序因竞争条件而崩溃。我将ciContext的初始化移到了我的loadCamera方法中，因此它没有崩溃。
<强>更新
我注意到的另一件事是，在互联网上的各种教程和博客文章中，声明let ciContext = CIContext(EAGLContext: EAGLContext(API: .OpenGLES2))在两个单独的声明中声明，以便它成为
let eaglContext = EAGLContext(API: .OpenGLES2)
let ciContext = CIContext(EAGLContext: eaglContext)
我仍然不知道究竟是什么导致应用程序崩溃，但这两个更改似乎解决了问题
正确答案
终于找到了罪魁祸首。在我使用ciContext的viewController中，我有一个未被无效的计时器，因此保留了对viewController的强引用。在每次后续访问中，它将创建一个新的viewController，而前一个从未从内存中释放。这导致记忆加速。一旦它超过某个阈值，ciContext intialiser将返回nil，因为内存不足会导致应用程序崩溃。