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Xiao Ling
Xiao Ling

Posted on • Originally published at dynamsoft.com

How to Implement a Flutter QR Code Scanner Plugin for iOS in Swift

Previously, I wrote a blog post sharing how to implement a Flutter QR code scanner plugin for Android. For cross-platform mobile development, a plugin is not perfect if it does not support both Android and iOS. In this article, I am going to complement the iOS part of the plugin in order to bring the best development experience for mobile developers.

Flutter QR Code Scanner Plugin

https://pub.dev/packages/flutter_camera_qrcode_scanner

Dev Environment

  • M1 Mac
  • Xcode 13.2.1

Step-by-step Guide: Implement Flutter QR Code Scanner Plugin for iOS

Step 1: Get the Existing Flutter Plugin Project:

git clone https://github.com/yushulx/flutter_qrcode_scanner
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Step 2: Add Support for iOS

cd flutter_qrcode_scanner
flutter create --template=plugin --platforms=ios .
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Step 3: Install Dynamsoft Camera Enhancer and Dynamsoft Barcode Reader

Open iOS/flutter_camera_qrcode_scanner.podspec to add Dynamsoft Camera Enhancer 2.1.1 and Dynamsoft Barcode Reader 8.9.1:

s.dependency 'DynamsoftBarcodeReader', '8.9.1'
s.dependency 'DynamsoftCameraEnhancer', '2.1.1'
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The dependencies will be installed via pod install.

Activating Mobile QR Code SDK

Click here to get a valid license key for Dynamsoft Barcode Reader.

Step 4: Implement the Factory and the Platform View Using Swift Code

Since we have completed the code logic on the Dart side, we only need to focus on the platform-related code. According to the official tutorial and the Android part of the plugin, we can write Swift code for iOS as follows:

  1. Based on the structure of the Android QRCodeScanner class, we create a FLQRCodeScanner class in iOS/Classes/FLQRCodeScanner.swift:

    import Flutter
    import UIKit
    import DynamsoftBarcodeReader
    import DynamsoftCameraEnhancer
    
    public protocol DetectionHandler {
            func onDetected(data: NSArray)
        }
    
    class FLQRCodeScanner: NSObject, DBRTextResultDelegate {
    
        private var cameraView: DCECameraView
        private var dce: DynamsoftCameraEnhancer
        private var barcodeReader: DynamsoftBarcodeReader! = nil
        private var handler: DetectionHandler?
    
        init(cameraView: DCECameraView, dce: DynamsoftCameraEnhancer) {
            self.cameraView = cameraView
            self.cameraView.overlayVisible = true
            self.dce = dce
            super.init()
    
            createBarcodeReader(dce: dce)
        }
    
        func setDetectionHandler(handler: DetectionHandler) {
            self.handler = handler;
        }
    
        func createBarcodeReader(dce: DynamsoftCameraEnhancer) {
            // To activate the sdk, apply for a license key: https://www.dynamsoft.com/customer/license/trialLicense?product=dbr
            barcodeReader = DynamsoftBarcodeReader.init(license: "license-key")
            barcodeReader.setCameraEnhancer(dce)
    
            // Set text result call back to get barcode results.
            barcodeReader.setDBRTextResultDelegate(self, userData: nil)
    
            // Start the barcode decoding thread.
            barcodeReader.startScanning()
        }
    
        func textResultCallback(_ frameId: Int, results: [iTextResult]?, userData: NSObject?) {
            if results!.count > 0 {
                let outResults = NSMutableArray()
                for item in results! {
                    let subDic = NSMutableDictionary()
                    if item.barcodeFormat_2 != EnumBarcodeFormat2.Null {
                        subDic.setObject(item.barcodeFormatString_2 ?? "", forKey: "format" as NSCopying)
                    }else{
                        subDic.setObject(item.barcodeFormatString ?? "", forKey: "format" as NSCopying)
                    }
                    subDic.setObject(item.barcodeText ?? "", forKey: "text" as NSCopying)
                    let points = item.localizationResult?.resultPoints as! [CGPoint]
                    subDic.setObject(Int(points[0].x), forKey: "x1" as NSCopying)
                    subDic.setObject(Int(points[0].y), forKey: "y1" as NSCopying)
                    subDic.setObject(Int(points[1].x), forKey: "x2" as NSCopying)
                    subDic.setObject(Int(points[1].y), forKey: "y2" as NSCopying)
                    subDic.setObject(Int(points[2].x), forKey: "x3" as NSCopying)
                    subDic.setObject(Int(points[2].y), forKey: "y3" as NSCopying)
                    subDic.setObject(Int(points[3].x), forKey: "x4" as NSCopying)
                    subDic.setObject(Int(points[3].y), forKey: "y4" as NSCopying)
                    subDic.setObject(item.localizationResult?.angle ?? 0, forKey: "angle" as NSCopying)
                    outResults.add(subDic)
                }
    
                if handler != nil {
                    handler!.onDetected(data: outResults)
                }
            }
        } 
    
        func startScan() {
            cameraView.overlayVisible = true
            barcodeReader.startScanning()
        }
    
        func stopScan() {
            cameraView.overlayVisible = false
            barcodeReader.stopScanning()
        }
    
        func setBarcodeFormats(arg:NSDictionary) {
            let formats:Int = arg.value(forKey: "formats") as! Int
            let settings = try! barcodeReader!.getRuntimeSettings()
            settings.barcodeFormatIds = formats
            barcodeReader!.update(settings, error: nil)
        }
    
        func setLicense(license: String) {
            barcodeReader.license = license
        }
    }
    
  2. Then we create a FLNativeView class in iOS/Classes/FLNativeView.swift to implement the camera view:

    import Flutter
    import UIKit
    import DynamsoftCameraEnhancer
    
    class FLNativeView: NSObject, FlutterPlatformView, DetectionHandler {
        private var _view: UIView
        private var messenger: FlutterBinaryMessenger
        private var channel: FlutterMethodChannel
        private var qrCodeScanner: FLQRCodeScanner
        init(
            frame: CGRect,
            viewIdentifier viewId: Int64,
            arguments args: Any?,
            binaryMessenger: FlutterBinaryMessenger
        ) {
            self.messenger = binaryMessenger
            let cameraView = DCECameraView.init(frame: frame)
            let dce = DynamsoftCameraEnhancer.init(view: cameraView)
            dce.open()
            dce.setFrameRate(30)
            _view = cameraView
    
            qrCodeScanner = FLQRCodeScanner.init(cameraView: cameraView, dce: dce)
    
            channel = FlutterMethodChannel(name: "com.dynamsoft.flutter_camera_qrcode_scanner/nativeview_" + String(viewId), binaryMessenger: messenger)
    
            super.init()
    
            qrCodeScanner.setDetectionHandler(handler: self)
            channel.setMethodCallHandler({
            (call: FlutterMethodCall, result: @escaping FlutterResult) -> Void in
                switch call.method {
                    case "startScanning":
                        self.qrCodeScanner.startScan()
                        result(.none)
                    case "stopScanning":
                        self.qrCodeScanner.stopScan()
                        result(.none)
                    case "setLicense":
                        self.qrCodeScanner.setLicense(license: (call.arguments as! NSDictionary).value(forKey: "license") as! String)
                        result(.none)
                    case "setBarcodeFormats":
                        self.qrCodeScanner.setBarcodeFormats(arg: call.arguments as! NSDictionary)
                        result(.none)
                    default:
                        result(.none)
                    }
            })
        }
    
        func view() -> UIView {
            return _view
        }
    
        func onDetected(data: NSArray) {
            DispatchQueue.main.async {
                    self.channel.invokeMethod("onDetected", arguments: data)
                }
        }
    }
    
    

    The native view contains a channel to handle Flutter method calls (from Dart to native). It also triggers the onDetected callback function (from native to Dart). When a QR code is detected, the channel will send the QR information from the native side to the Dart side .

  3. Next, create a FLNativeViewFactory class in iOS/Classes/FLNativeViewFactory.swift to initialize the native view:

    import Flutter
    import UIKit
    
    class FLNativeViewFactory: NSObject, FlutterPlatformViewFactory {
        private var messenger: FlutterBinaryMessenger
    
        init(messenger: FlutterBinaryMessenger) {
            self.messenger = messenger
            super.init()
        }
    
        func create(
            withFrame frame: CGRect,
            viewIdentifier viewId: Int64,
            arguments args: Any?
        ) -> FlutterPlatformView {
            return FLNativeView(
                frame: frame,
                viewIdentifier: viewId,
                arguments: args,
                binaryMessenger: messenger
            )
        }
    }
    
  4. The final step is to register the factory in iOS/Classes/SwiftFlutterCameraQrcodeScannerPlugin.swift:

    import Flutter
    import UIKit
    
    public class SwiftFlutterCameraQrcodeScannerPlugin: NSObject, FlutterPlugin {
      public static func register(with registrar: FlutterPluginRegistrar) {  
        let factory = FLNativeViewFactory(messenger: registrar.messenger())
        registrar.register(factory, withId: "com.dynamsoft.flutter_camera_qrcode_scanner/nativeview")
      }
    }
    

So far, the native Swift code for plugin is done.

Step 5: Test the QR code scanner in Flutter

  1. Go to the example folder and add the camera access permission to ios/Runner/Info.plist:

    <key>NSCameraUsageDescription</key>
    <string>Can I use the camera please?</string>
    <key>NSMicrophoneUsageDescription</key>
    <string>Can I use the mic please?</string>
    
  2. Run the example on iOS devices:

    flutter run
    

    Flutter iOS QR code scanner

Source Code

https://github.com/yushulx/flutter_qrcode_scanner

Top comments (0)

Regex for lazy developers

regex for lazy devs

You know who you are. Sorry for the callout 😆