I am making a phone number recognition app based off of Apple’s example code. I am fairly new to swift and coding in general. When I run the project I get the "Thread 1: EXC_BAD_ACCESS (code=257, address=0x7e700019ec0ad79)" error on line 68 "previewView.session = captureSession" . I think it has something to do with line 26 "@IBOutlet weak var previewView: PreviewView!" ?
I have a view controller with 2 views and one label. The IB Outlets seem fine for two of them but does not look the same for line 26.. the color of the text PreviewView! is gray instead of blue like the others. Could this be the problem?
import AVFoundation
import Vision
class TextScanViewController: UIViewController {
// MARK: - UI objects
@IBOutlet weak var previewView: PreviewView!
@IBOutlet weak var cutoutView: UIView!
@IBOutlet weak var numberView: UILabel!
var maskLayer = CAShapeLayer()
// Device orientation. Updated whenever the orientation changes to a
// different supported orientation.
var currentOrientation = UIDeviceOrientation.portrait
// MARK: - Capture related objects
private let captureSession = AVCaptureSession()
let captureSessionQueue = DispatchQueue(label: "com.example.apple-samplecode.CaptureSessionQueue")
var captureDevice: AVCaptureDevice?
var videoDataOutput = AVCaptureVideoDataOutput()
let videoDataOutputQueue = DispatchQueue(label: "com.example.apple-samplecode.VideoDataOutputQueue")
// MARK: - Region of interest (ROI) and text orientation
// Region of video data output buffer that recognition should be run on.
// Gets recalculated once the bounds of the preview layer are known.
var regionOfInterest = CGRect(x: 0, y: 0, width: 1, height: 1)
// Orientation of text to search for in the region of interest.
var textOrientation = CGImagePropertyOrientation.up
// MARK: - Coordinate transforms
var bufferAspectRatio: Double!
// Transform from UI orientation to buffer orientation.
var uiRotationTransform = CGAffineTransform.identity
// Transform bottom-left coordinates to top-left.
var bottomToTopTransform = CGAffineTransform(scaleX: 1, y: -1).translatedBy(x: 0, y: -1)
// Transform coordinates in ROI to global coordinates (still normalized).
var roiToGlobalTransform = CGAffineTransform.identity
// Vision -> AVF coordinate transform.
var visionToAVFTransform = CGAffineTransform.identity
// MARK: - View controller methods
override func viewDidLoad() {
super.viewDidLoad()
// Set up preview view.
previewView.session = captureSession
// Set up cutout view.
cutoutView.backgroundColor = UIColor.gray.withAlphaComponent(0.5)
maskLayer.backgroundColor = UIColor.clear.cgColor
maskLayer.fillRule = .evenOdd
cutoutView.layer.mask = maskLayer
// Starting the capture session is a blocking call. Perform setup using
// a dedicated serial dispatch queue to prevent blocking the main thread.
captureSessionQueue.async {
self.setupCamera()
// Calculate region of interest now that the camera is setup.
DispatchQueue.main.async {
// Figure out initial ROI.
self.calculateRegionOfInterest()
}
}
}
override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
super.viewWillTransition(to: size, with: coordinator)
// Only change the current orientation if the new one is landscape or
// portrait. You can't really do anything about flat or unknown.
let deviceOrientation = UIDevice.current.orientation
if deviceOrientation.isPortrait || deviceOrientation.isLandscape {
currentOrientation = deviceOrientation
}
// Handle device orientation in the preview layer.
if let videoPreviewLayerConnection = previewView.videoPreviewLayer.connection {
if let newVideoOrientation = AVCaptureVideoOrientation(deviceOrientation: deviceOrientation) {
videoPreviewLayerConnection.videoOrientation = newVideoOrientation
}
}
// Orientation changed: figure out new region of interest (ROI).
calculateRegionOfInterest()
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
updateCutout()
}
// MARK: - Setup
func calculateRegionOfInterest() {
// In landscape orientation the desired ROI is specified as the ratio of
// buffer width to height. When the UI is rotated to portrait, keep the
// vertical size the same (in buffer pixels). Also try to keep the
// horizontal size the same up to a maximum ratio.
let desiredHeightRatio = 0.15
let desiredWidthRatio = 0.6
let maxPortraitWidth = 0.8
// Figure out size of ROI.
let size: CGSize
if currentOrientation.isPortrait || currentOrientation == .unknown {
size = CGSize(width: min(desiredWidthRatio * bufferAspectRatio, maxPortraitWidth), height: desiredHeightRatio / bufferAspectRatio)
} else {
size = CGSize(width: desiredWidthRatio, height: desiredHeightRatio)
}
// Make it centered.
regionOfInterest.origin = CGPoint(x: (1 - size.width) / 2, y: (1 - size.height) / 2)
regionOfInterest.size = size
// ROI changed, update transform.
setupOrientationAndTransform()
// Update the cutout to match the new ROI.
DispatchQueue.main.async {
// Wait for the next run cycle before updating the cutout. This
// ensures that the preview layer already has its new orientation.
self.updateCutout()
}
}
func updateCutout() {
// Figure out where the cutout ends up in layer coordinates.
let roiRectTransform = bottomToTopTransform.concatenating(uiRotationTransform)
let cutout = previewView.videoPreviewLayer.layerRectConverted(fromMetadataOutputRect: regionOfInterest.applying(roiRectTransform))
// Create the mask.
let path = UIBezierPath(rect: cutoutView.frame)
path.append(UIBezierPath(rect: cutout))
maskLayer.path = path.cgPath
// Move the number view down to under cutout.
var numFrame = cutout
numFrame.origin.y += numFrame.size.height
numberView.frame = numFrame
}
func setupOrientationAndTransform() {
// Recalculate the affine transform between Vision coordinates and AVF coordinates.
// Compensate for region of interest.
let roi = regionOfInterest
roiToGlobalTransform = CGAffineTransform(translationX: roi.origin.x, y: roi.origin.y).scaledBy(x: roi.width, y: roi.height)
// Compensate for orientation (buffers always come in the same orientation).
switch currentOrientation {
case .landscapeLeft:
textOrientation = CGImagePropertyOrientation.up
uiRotationTransform = CGAffineTransform.identity
case .landscapeRight:
textOrientation = CGImagePropertyOrientation.down
uiRotationTransform = CGAffineTransform(translationX: 1, y: 1).rotated(by: CGFloat.pi)
case .portraitUpsideDown:
textOrientation = CGImagePropertyOrientation.left
uiRotationTransform = CGAffineTransform(translationX: 1, y: 0).rotated(by: CGFloat.pi / 2)
default: // We default everything else to .portraitUp
textOrientation = CGImagePropertyOrientation.right
uiRotationTransform = CGAffineTransform(translationX: 0, y: 1).rotated(by: -CGFloat.pi / 2)
}
// Full Vision ROI to AVF transform.
visionToAVFTransform = roiToGlobalTransform.concatenating(bottomToTopTransform).concatenating(uiRotationTransform)
}
func setupCamera() {
guard let captureDevice = AVCaptureDevice.default(.builtInWideAngleCamera, for: AVMediaType.video, position: .back) else {
print("Could not create capture device.")
return
}
self.captureDevice = captureDevice
// NOTE:
// Requesting 4k buffers allows recognition of smaller text but will
// consume more power. Use the smallest buffer size necessary to keep
// down battery usage.
if captureDevice.supportsSessionPreset(.hd4K3840x2160) {
captureSession.sessionPreset = AVCaptureSession.Preset.hd4K3840x2160
bufferAspectRatio = 3840.0 / 2160.0
} else {
captureSession.sessionPreset = AVCaptureSession.Preset.hd1920x1080
bufferAspectRatio = 1920.0 / 1080.0
}
guard let deviceInput = try? AVCaptureDeviceInput(device: captureDevice) else {
print("Could not create device input.")
return
}
if captureSession.canAddInput(deviceInput) {
captureSession.addInput(deviceInput)
}
// Configure video data output.
videoDataOutput.alwaysDiscardsLateVideoFrames = true
videoDataOutput.setSampleBufferDelegate(self, queue: videoDataOutputQueue)
videoDataOutput.videoSettings = [kCVPixelBufferPixelFormatTypeKey as String: kCVPixelFormatType_420YpCbCr8BiPlanarFullRange]
if captureSession.canAddOutput(videoDataOutput) {
captureSession.addOutput(videoDataOutput)
// NOTE:
// There is a trade-off to be made here. Enabling stabilization will
// give temporally more stable results and should help the recognizer
// converge. But if it's enabled the VideoDataOutput buffers don't
// match what's displayed on screen, which makes drawing bounding
// boxes very hard. Disable it in this app to allow drawing detected
// bounding boxes on screen.
videoDataOutput.connection(with: AVMediaType.video)?.preferredVideoStabilizationMode = .off
} else {
print("Could not add VDO output")
return
}
// Set zoom and autofocus to help focus on very small text.
do {
try captureDevice.lockForConfiguration()
captureDevice.videoZoomFactor = 2
captureDevice.autoFocusRangeRestriction = .near
captureDevice.unlockForConfiguration()
} catch {
print("Could not set zoom level due to error: (error)")
return
}
captureSession.startRunning()
}
// MARK: - UI drawing and interaction
func showString(string: String) {
// Found a definite number.
// Stop the camera synchronously to ensure that no further buffers are
// received. Then update the number view asynchronously.
captureSessionQueue.sync {
self.captureSession.stopRunning()
DispatchQueue.main.async {
self.numberView.text = string
self.numberView.isHidden = false
}
}
}
@IBAction func handleTap(_ sender: UITapGestureRecognizer) {
captureSessionQueue.async {
if !self.captureSession.isRunning {
self.captureSession.startRunning()
}
DispatchQueue.main.async {
self.numberView.isHidden = true
}
}
}
}
// MARK: - AVCaptureVideoDataOutputSampleBufferDelegate
extension TextScanViewController: AVCaptureVideoDataOutputSampleBufferDelegate {
func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
// This is implemented in VisionViewController.
}
}
// MARK: - Utility extensions
extension AVCaptureVideoOrientation {
init?(deviceOrientation: UIDeviceOrientation) {
switch deviceOrientation {
case .portrait: self = .portrait
case .portraitUpsideDown: self = .portraitUpsideDown
case .landscapeLeft: self = .landscapeRight
case .landscapeRight: self = .landscapeLeft
default: return nil
}
}
}
2
Answers
Check the connection inspector in your storyboard or xib and check if
previewViewif it has a single reference, it may be that you have more than one or in any case no reference to your IBOuletIf you try to reference an
@IBOutletobject that has not been properly connected, you will get this error:Since that is not the error you are getting, it must be something else.
Almost certainly, you added a
UIViewand connected it to:but forgot to set the Custom Class.
When you select that
UIViewin Storyboard, this:should look like this:
(Ignore the "Module: qt122022" — it will auto-fill with the name of your project. Mine just happens to be named qt122022.)