Flutter插件开发之HmsScanKit实现示例详解
作者:Fitem
前沿
从事Flutter开发以来,一直都是使用已有的插件,没有自己开发过。最近同事推荐让我使用华为的扫码SDK(hms_scan_kit),正好借此机会来开发一个Flutter的原生插件。算是对最近的插件学习做一个简单的总结。
效果图
我们先看一下实现的扫码效果:点击LoadScanKit按钮调起插件的扫码功能,扫码成功后在界面显示扫码结果。
相关知识点
1. Flutter Packages
通过使用 package(的模式)可以创建易于共享的模块化代码。一个最基本的 package 由以下内容构成:
- pubspec.yaml 文件
用于定义 package 名称、版本号、作者等其他信息的元数据文件。- lib 目录
包含共享代码的 lib 目录,其中至少包含一个 <package-name>.dart 文件。
2. Package类别
Package包分为二种:
- 纯Dart库(Dart packages)
- 只用Dart编写的传统package,比如 path。
- 原生插件(Plugin packages)
- 使用Dart编写的,按需使用Java或 Kotlin、Objective-C或Swift 分别在Android或iOS平台实现的package。
3. 原生插件开发步骤
- 创建package
- 想要创建原生插件 package,请使用带有 --template=plugin 标志的 flutter create 命令
flutter create --org com.example --template=plugin --platforms=android,ios -a kotlin hello
实现package a. 定义 package API(.dart) b. 添加 Android/iOS 平台代码(.kt/.swift) C. 关联 API 和平台代码
指定插件支持的平台,比如hms_scan插件就如下定义:
name: flutter_hms_scan description: A new Flutter project. version: 0.0.1 homepage: environment: sdk: ">=2.15.1 <3.0.0" flutter: ">=2.5.0" flutter: plugin: platforms: android: package: com.fitem.flutter_hms_scan pluginClass: HmsScanPlugin ios: pluginClass: HmsScanPlugin
备注:如果使用IDE(比如Android Studio)直接在创建Flutter项目处选择Plugin类型即可,IDE会创建插件模板并实现获取平台系统版本的example,无需上面的步骤
- Dart对应原生类型:
Dart | kotlin | Swift |
---|---|---|
null | null | nil |
bool | Boolean | NSNumber(value: Bool) |
int | Int | NSNumber(value: Int32) |
int | Long | NSNumber(value: Int) |
double | Double | NSNumber(value: Double) |
String | String | String |
Uint8List | ByteArray | FlutterStandardTypedData(bytes: Data) |
Int32List | IntArray | FlutterStandardTypedData(int32: Data) |
Int64List | LongArray | FlutterStandardTypedData(int64: Data) |
Float32List | FloatArray | FlutterStandardTypedData(float32: Data) |
Float64List | DoubleArray | FlutterStandardTypedData(float64: Data) |
List | List | Array |
Map | HashMap | Dictionary |
- Flutter的plugin通信流程如下:
HmsScan插件的实现
前面说了这么多,终于进入正题,下面我们开始HmsScan插件的开发吧。
1. 定义 package API:
class FlutterHmsScan { // 创建插件 static const MethodChannel _channel = MethodChannel('hms_scan'); // 定义调用方法 static Future<ScanBean> loadScanKit() async { return await _channel .invokeMethod("loadScanKit") .then((value) => scanBeanFromJson(json.encode(value))); } }
2. Android代码实现:
a. 使用IDE打开Android目录,根据官方SDK导入库
// scankitSDK implementation 'com.huawei.hms:scanplus:2.4.0.301' // 需要在repositories中导入url maven {url 'https://developer.huawei.com/repo/'}
b. 继承FlutterPlugin类,接入Flutter管道。由于sdk用到权限请求和onActivityResult的回调,因此我们需要继承ActivityAware对Activity添加监听。其中registerWith()方法是为了适配老版本Flutter的兼容。
class HmsScanPlugin : FlutterPlugin, ActivityAware { /// The MethodChannel that will the communication between Flutter and native Android /// /// This local reference serves to register the plugin with the Flutter Engine and unregister it /// when the Flutter Engine is detached from the Activity private lateinit var mScanLauncher: ScanLauncher private lateinit var mHandler: MethodCallHandlerImpl /** * 老版本Flutter兼容 */ fun registerWith(registrar: Registrar) { mScanLauncher = ScanLauncher(registrar.context(), registrar.activity()) mHandler = MethodCallHandlerImpl(mScanLauncher) mHandler.startService(registrar.messenger()) registrar.addActivityResultListener(mHandler) registrar.addRequestPermissionsResultListener(mHandler) } override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) { mScanLauncher = ScanLauncher(flutterPluginBinding.applicationContext, null) mHandler = MethodCallHandlerImpl(mScanLauncher) mHandler.startService(flutterPluginBinding.binaryMessenger) } override fun onDetachedFromEngine(@NonNull binding: FlutterPlugin.FlutterPluginBinding) { mHandler.stopService() } override fun onAttachedToActivity(binding: ActivityPluginBinding) { mScanLauncher.activity = binding.activity binding.addActivityResultListener(mHandler) binding.addRequestPermissionsResultListener(mHandler) } override fun onDetachedFromActivity() { mScanLauncher.activity = null } override fun onDetachedFromActivityForConfigChanges() { onDetachedFromActivity() } override fun onReattachedToActivityForConfigChanges(binding: ActivityPluginBinding) { onAttachedToActivity(binding) } }
c. 考虑到HmsScanPlugin职责过多,这里使用MethodCallHandlerImpl进行分离解耦,专门处理Flutter管道的通信。
/** * 插件方法监听 * Created by Fitem on 2022/3/2. */ class MethodCallHandlerImpl(var scanLauncher: ScanLauncher) : MethodChannel.MethodCallHandler, MethodCallHandlerListener, PluginRegistry.ActivityResultListener, PluginRegistry.RequestPermissionsResultListener { private lateinit var channel: MethodChannel override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) { when (call.method) { "getPlatformVersion" -> { result.success("Android ${android.os.Build.VERSION.RELEASE}") } "loadScanKit" -> { scanLauncher.loadScanKit(call, result) } else -> { result.notImplemented() } } } override fun startService(binaryMessenger: BinaryMessenger) { channel = MethodChannel(binaryMessenger, "hms_scan") channel.setMethodCallHandler(this) } override fun stopService() { channel.setMethodCallHandler(null) } override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?): Boolean { if (resultCode != Activity.RESULT_OK || data == null) { return false } return scanLauncher.onActivityResult(requestCode, resultCode, data) } override fun onRequestPermissionsResult( requestCode: Int, permissions: Array<out String>?, grantResults: IntArray? ): Boolean { if (permissions == null || grantResults == null) { return false } return scanLauncher.onRequestPermissionResult(requestCode, permissions, grantResults) } } // 管道通信生命周期的绑定 interface MethodCallHandlerListener { fun startService(binaryMessenger: BinaryMessenger) fun stopService() }
d. 最后通过ScanLauncher来专门处理扫码功能的相关实现
class ScanLauncher(var applicationContext: Context, var activity: Activity?) { companion object { const val CAMERA_REQ_CODE = 111 const val DEFINED_CODE = 222 const val BITMAP_CODE = 333 const val MULTIPROCESSOR_SYN_CODE = 444 const val MULTIPROCESSOR_ASYN_CODE = 555 const val GENERATE_CODE = 666 const val DECODE = 1 const val GENERATE = 2 const val REQUEST_CODE_SCAN_ONE = 0X01 const val REQUEST_CODE_DEFINE = 0X0111 const val REQUEST_CODE_SCAN_MULTI = 0X011 const val DECODE_MODE = "decode_mode" const val RESULT = "SCAN_RESULT" const val SCAN_STATUS = "scanStatus" const val CODE_FORMAT = "codeFormat" const val RESULT_TYPE = "resultType" const val CODE_RESULT = "codeResult" } private var result: MethodChannel.Result? = null /** * 扫码 */ fun loadScanKit(call: MethodCall, result: MethodChannel.Result) { this.result = result requestPermission(CAMERA_REQ_CODE, DECODE) } /** * Apply for permissions. */ private fun requestPermission(requestCode: Int, mode: Int) { if (activity == null) { result?.success(mapOf(SCAN_STATUS to false)) return } if (mode == DECODE) { decodePermission(requestCode) } else if (mode == GENERATE) { generatePermission(requestCode) } } /** * Apply for permissions. */ private fun decodePermission(requestCode: Int) { ActivityCompat.requestPermissions( activity!!, arrayOf(Manifest.permission.CAMERA, Manifest.permission.READ_EXTERNAL_STORAGE), requestCode ) } /** * Apply for permissions. */ private fun generatePermission(requestCode: Int) { ActivityCompat.requestPermissions( activity!!, arrayOf(Manifest.permission.WRITE_EXTERNAL_STORAGE), requestCode ) } fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent): Boolean { //Default View if (requestCode == REQUEST_CODE_SCAN_ONE) { val obj: HmsScan? = data.getParcelableExtra(ScanUtil.RESULT) if (obj != null) { result?.success( mapOf( SCAN_STATUS to true, CODE_FORMAT to getCodeFormat(obj.scanType), RESULT_TYPE to getResultType(obj), CODE_RESULT to obj.originalValue ) ) return true } //MultiProcessor & Bitmap } return false } fun onRequestPermissionResult( requestCode: Int, permissions: Array<out String>, grantResults: IntArray ): Boolean { if (grantResults.size < 2 || grantResults[0] != PackageManager.PERMISSION_GRANTED || grantResults[1] != PackageManager.PERMISSION_GRANTED) { return false } //Default View Mode if (requestCode == CAMERA_REQ_CODE) { ScanUtil.startScan( activity, REQUEST_CODE_SCAN_ONE, HmsScanAnalyzerOptions.Creator().create() ) return true } return false } /** * 获取CodeFormat */ private fun getCodeFormat(codeFormat: Int): String { return when (codeFormat) { HmsScan.QRCODE_SCAN_TYPE -> "QR code" HmsScan.AZTEC_SCAN_TYPE -> "AZTEC code" HmsScan.DATAMATRIX_SCAN_TYPE -> "DATAMATRIX code" HmsScan.PDF417_SCAN_TYPE -> "PDF417 code" HmsScan.CODE93_SCAN_TYPE -> "CODE93" HmsScan.CODE39_SCAN_TYPE -> "CODE39" HmsScan.CODE128_SCAN_TYPE -> "CODE128" HmsScan.EAN13_SCAN_TYPE -> "EAN13 code" HmsScan.EAN8_SCAN_TYPE -> "EAN8 code" HmsScan.ITF14_SCAN_TYPE -> "ITF14 code" HmsScan.UPCCODE_A_SCAN_TYPE -> "UPCCODE_A" HmsScan.UPCCODE_E_SCAN_TYPE -> "UPCCODE_E" HmsScan.CODABAR_SCAN_TYPE -> "CODABAR" else -> "OTHER" } } /** * 获取ResultType */ private fun getResultType(hmsScan: HmsScan): String { return when (hmsScan.scanType) { HmsScan.QRCODE_SCAN_TYPE -> when (hmsScan.scanTypeForm) { HmsScan.QRCODE_SCAN_TYPE -> "Text" HmsScan.EVENT_INFO_FORM -> "Event" HmsScan.CONTACT_DETAIL_FORM -> "Contact" HmsScan.DRIVER_INFO_FORM -> "License" HmsScan.EMAIL_CONTENT_FORM -> "Email" HmsScan.LOCATION_COORDINATE_FORM -> "Location" HmsScan.TEL_PHONE_NUMBER_FORM -> "Tel" HmsScan.SMS_FORM -> "SMS" HmsScan.WIFI_CONNECT_INFO_FORM -> "Wi-Fi" HmsScan.URL_FORM -> "WebSite" HmsScan.URL_FORM -> "WebSite" else -> "Text" } HmsScan.EAN13_SCAN_TYPE -> when (hmsScan.scanTypeForm) { HmsScan.ISBN_NUMBER_FORM -> "ISBN" HmsScan.ARTICLE_NUMBER_FORM -> "Product" else -> "Text" } HmsScan.EAN8_SCAN_TYPE, HmsScan.UPCCODE_A_SCAN_TYPE, HmsScan.UPCCODE_E_SCAN_TYPE -> when (hmsScan.scanTypeForm) { HmsScan.ARTICLE_NUMBER_FORM -> "Product" else -> "Text" } else -> "Text" } } }
最后在AndroidManifest.xml中添加需要的权限:
<!--相机权限--> <uses-permission android:name="android.permission.CAMERA" /> <!--文件读取权限--> <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
3. ios部分的实现
ios原本也是打算使用hms的,但是官方居然2年没有更新了,并且不支持bitcode版本、不支持cocopod,demo也无法正常运行。经过一番尝试后,决定放弃使用该库,换成了MTBBarcodeScanner库。(ios新人一个,如果有精通IOS的同学们欢迎指教!)
a. 通过SwiftHmsScanPlugin创建Flutter管道
public class SwiftHmsScanPlugin: NSObject, FlutterPlugin, BarcodeScannerViewControllerDelegate { private var result: FlutterResult? private var hostViewController: UIViewController? public static func register(with registrar: FlutterPluginRegistrar) { let channel = FlutterMethodChannel(name: "hms_scan", binaryMessenger: registrar.messenger()) let instance = SwiftHmsScanPlugin() registrar.addMethodCallDelegate(instance, channel: channel) } public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) { self.result = result if ("loadScanKit" == call.method) { loadScanKit() } else { result("iOS " + UIDevice.current.systemVersion) } } public func loadScanKit() { if let rootVC = UIApplication.shared.keyWindow?.rootViewController { hostViewController = topViewController(base:rootVC) } else if let window = UIApplication.shared.delegate?.window,let rootVC = window?.rootViewController { hostViewController = topViewController(base:rootVC) } let scannerViewController = BarcodeScannerViewController() let navigationController = UINavigationController(rootViewController: scannerViewController) if #available(iOS 13.0, *) { navigationController.modalPresentationStyle = .fullScreen } scannerViewController.delegate = self hostViewController?.present(navigationController, animated: false) } private func topViewController(base: UIViewController?) -> UIViewController? { if let nav = base as? UINavigationController { return topViewController(base: nav.visibleViewController) } else if let tab = base as? UITabBarController, let selected = tab.selectedViewController { return topViewController(base: selected) } else if let presented = base?.presentedViewController { return topViewController(base: presented) } return base } func didScanBarcodeWithResult(_ controller: BarcodeScannerViewController?, scanResult: ScanResult) { result?(["codeResult":scanResult.rawContent, "scanStatus" : String(true), "resultType": String(scanResult.format.rawValue)]) } func didFailWithErrorCode(_ controller: BarcodeScannerViewController?, errorCode: String) { result?(["scanStatus" : String(false)]) } }
b. BarcodeScannerViewController实现扫码功能
class BarcodeScannerViewController: UIViewController { private var previewView: UIView? private var scanRect: ScannerOverlay? private var scanner: MTBBarcodeScanner? private let formatMap = [ BarcodeFormat.aztec : AVMetadataObject.ObjectType.aztec, BarcodeFormat.code39 : AVMetadataObject.ObjectType.code39, BarcodeFormat.code93 : AVMetadataObject.ObjectType.code93, BarcodeFormat.code128 : AVMetadataObject.ObjectType.code128, BarcodeFormat.dataMatrix : AVMetadataObject.ObjectType.dataMatrix, BarcodeFormat.ean8 : AVMetadataObject.ObjectType.ean8, BarcodeFormat.ean13 : AVMetadataObject.ObjectType.ean13, BarcodeFormat.interleaved2Of5 : AVMetadataObject.ObjectType.interleaved2of5, BarcodeFormat.pdf417 : AVMetadataObject.ObjectType.pdf417, BarcodeFormat.qr : AVMetadataObject.ObjectType.qr, BarcodeFormat.upce : AVMetadataObject.ObjectType.upce, ] var delegate: BarcodeScannerViewControllerDelegate? private var device: AVCaptureDevice? { return AVCaptureDevice.default(for: .video) } private var isFlashOn: Bool { return device != nil && (device?.flashMode == AVCaptureDevice.FlashMode.on || device?.torchMode == .on) } private var hasTorch: Bool { return device?.hasTorch ?? false } override func viewDidLoad() { super.viewDidLoad() UIDevice.current.endGeneratingDeviceOrientationNotifications() #if targetEnvironment(simulator) view.backgroundColor = .lightGray #endif previewView = UIView(frame: view.bounds) if let previewView = previewView { previewView.autoresizingMask = [.flexibleWidth, .flexibleHeight] view.addSubview(previewView) } setupScanRect(view.bounds) scanner = MTBBarcodeScanner(previewView: previewView) navigationItem.leftBarButtonItem = UIBarButtonItem(title: "cancel", style: .plain, target: self, action: #selector(cancel) ) updateToggleFlashButton() } override func viewDidAppear(_ animated: Bool) { super.viewDidAppear(animated) if scanner!.isScanning() { scanner!.stopScanning() } UIDevice.current.endGeneratingDeviceOrientationNotifications() scanRect?.startAnimating() MTBBarcodeScanner.requestCameraPermission(success: { success in if success { self.startScan() } else { #if !targetEnvironment(simulator) self.errorResult(errorCode: "PERMISSION_NOT_GRANTED") #endif } }) } override func viewWillDisappear(_ animated: Bool) { scanner?.stopScanning() scanRect?.stopAnimating() UIDevice.current.beginGeneratingDeviceOrientationNotifications() if isFlashOn { setFlashState(false) } super.viewWillDisappear(animated) } override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) { super.viewWillTransition(to: size, with: coordinator) setupScanRect(CGRect(origin: CGPoint(x: 0, y:0), size: size )) } private func setupScanRect(_ bounds: CGRect) { if scanRect != nil { scanRect?.stopAnimating() scanRect?.removeFromSuperview() } scanRect = ScannerOverlay(frame: bounds) if let scanRect = scanRect { scanRect.translatesAutoresizingMaskIntoConstraints = false scanRect.backgroundColor = UIColor.clear view.addSubview(scanRect) scanRect.startAnimating() } } private func startScan() { do { try scanner!.startScanning(with: cameraFromConfig, resultBlock: { codes in if let code = codes?.first { let codeType = self.formatMap.first(where: { $0.value == code.type }); let scanResult = ScanResult.with { $0.type = .barcode $0.rawContent = code.stringValue ?? "" $0.format = codeType?.key ?? .unknown $0.formatNote = codeType == nil ? code.type.rawValue : "" } self.scanner!.stopScanning() self.scanResult(scanResult) } }) } catch { self.scanResult(ScanResult.with { $0.type = .error $0.rawContent = "\(error)" $0.format = .unknown }) } } @objc private func cancel() { scanResult( ScanResult.with { $0.type = .cancelled $0.format = .unknown }); } @objc private func onToggleFlash() { setFlashState(!isFlashOn) } private func updateToggleFlashButton() { if !hasTorch { return } let buttonText = isFlashOn ? "flash_off" : "flash_on" navigationItem.rightBarButtonItem = UIBarButtonItem(title: buttonText, style: .plain, target: self, action: #selector(onToggleFlash) ) } private func setFlashState(_ on: Bool) { if let device = device { guard device.hasFlash && device.hasTorch else { return } do { try device.lockForConfiguration() } catch { return } device.flashMode = on ? .on : .off device.torchMode = on ? .on : .off device.unlockForConfiguration() updateToggleFlashButton() } } private func errorResult(errorCode: String){ delegate?.didFailWithErrorCode(self, errorCode: errorCode) dismiss(animated: false) } private func scanResult(_ scanResult: ScanResult){ self.delegate?.didScanBarcodeWithResult(self, scanResult: scanResult) dismiss(animated: false) } private var cameraFromConfig: MTBCamera { return .back } }
c. 最后需要在example的ios目录Info.plist文件中添加相机权限:
// example/ios/Runner/Info.plist <key>NSCameraUsageDescription</key> <string>Camera permission is required for barcode scanning.</string>
至此,一个简单的应用于Android、iOS的plugin插件已完成。
4. 需要注意的点
- 使用Android Studio右键选择Flutter即可通过Android Studio和Xcode打开项目,如图:
- Android目录打开后,若看不到插件module,可以选择Project Files模式下查看,如图:
- ios目录打开前,需要进入example目录输入命令 flutter build ios,待编译完成后再通过Xcode打开。
总结
Plugin原生插件其实就是基于Flutter提供的管道进行通信,和原生开发的使用并无太大区别。但需要我们对原生代码的调用有一个基本的了解,然后引入其他原生开发库进行调用。最后附上项目地址:flutter_hms_scan
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