Bugfix/crash ios flutter engine rewrite

ios/Classes/CustomLogger.swift

@@ -5,10 +5,15 @@
 //  Created by Dimmy Maenhout on 21/12/2020.
 //
 
+import os
 import Foundation
 struct CustomLogger {
 
     static func log(message: String) {
+        if #available(iOS 10.0, *) {
+            let app = OSLog(subsystem: "com.icapps.background_location_tracker", category: "background tracker")
+            os_log("🔥 background-location log: %{public}@", log: app, type: .error, message)
+        }
         if SharedPrefsUtil.isLoggingEnabled() {
             print(message)
         }

ios/Classes/LocationManager.swift

@@ -14,6 +14,10 @@ class LocationManager {
         let manager = CLLocationManager()
         manager.activityType = .automotiveNavigation
         manager.desiredAccuracy = kCLLocationAccuracyBest
+        manager.pausesLocationUpdatesAutomatically = false
+        if #available(iOS 11, *) {
+            manager.showsBackgroundLocationIndicator = true
+        }
         if #available(iOS 9.0, *) {
             manager.allowsBackgroundLocationUpdates = true
         }

ios/Classes/SwiftBackgroundLocationTrackerPlugin.swift

@@ -6,9 +6,16 @@ public class SwiftBackgroundLocationTrackerPlugin: FlutterPluginAppLifeCycleDele
 
     static let identifier = "com.icapps.background_location_tracker"
 
-    private let flutterThreadLabelPrefix = "\(identifier).BackgroundLocationTracker"
+    private static let flutterThreadLabelPrefix = "\(identifier).BackgroundLocationTracker"
 
     private static var foregroundChannel: ForegroundChannel? = nil
+    private static var backgroundMethodChannel: FlutterMethodChannel? = nil
+
+    private static var flutterEngine: FlutterEngine? = nil
+    private static var hasRegisteredPlugins = false
+    private static var initializedBackgroundCallbacks = false
+    private static var initializedBackgroundCallbacksStarted = false
+    private static var locationData: [String: Any]? = nil
 
     private static var flutterPluginRegistrantCallback: FlutterPluginRegistrantCallback?
 
@@ -35,6 +42,55 @@ extension SwiftBackgroundLocationTrackerPlugin: FlutterPlugin {
         locationManager.delegate = self
         SwiftBackgroundLocationTrackerPlugin.foregroundChannel?.handle(call, result: result)
     }
+
+    public static func getFlutterEngine()-> FlutterEngine? {
+        if (flutterEngine == nil) {
+            let flutterEngine = FlutterEngine(name: flutterThreadLabelPrefix, project: nil, allowHeadlessExecution: true)
+
+            guard let callbackHandle = SharedPrefsUtil.getCallbackHandle(),
+                  let flutterCallbackInformation = FlutterCallbackCache.lookupCallbackInformation(callbackHandle) else {
+                CustomLogger.log(message: "No flutter callback cache ...")
+                return nil
+            }
+            flutterEngine.run(withEntrypoint: flutterCallbackInformation.callbackName, libraryURI: flutterCallbackInformation.callbackLibraryPath)
+            SwiftBackgroundLocationTrackerPlugin.flutterPluginRegistrantCallback?(flutterEngine)
+            self.flutterEngine = flutterEngine
+        }
+        return flutterEngine
+    }
+
+    public static func initBackgroundMethodChannel(flutterEngine: FlutterEngine) {
+        if (backgroundMethodChannel == nil) {
+            let backgroundMethodChannel = FlutterMethodChannel(name: SwiftBackgroundLocationTrackerPlugin.BACKGROUND_CHANNEL_NAME, binaryMessenger: flutterEngine.binaryMessenger)
+            backgroundMethodChannel.setMethodCallHandler { (call, result) in
+                switch call.method {
+                case BackgroundMethods.initialized.rawValue:
+                    initializedBackgroundCallbacks = true
+                    if let data = SwiftBackgroundLocationTrackerPlugin.locationData {
+                        CustomLogger.log(message: "Initialized with cached value, sending location update")
+                        sendLocationupdate(locationData: data)
+                    } else {
+                        CustomLogger.log(message: "Initialized without cached value")
+                    }
+                    result(true)
+                default:
+                    CustomLogger.log(message: "Not implemented method -> \(call.method)")
+                    result(FlutterMethodNotImplemented)
+                }
+            }
+            self.backgroundMethodChannel = backgroundMethodChannel
+        }
+    }
+
+    public static func sendLocationupdate(locationData: [String: Any]){
+        guard let backgroundMethodChannel = SwiftBackgroundLocationTrackerPlugin.backgroundMethodChannel else {
+            CustomLogger.log(message: "No background channel available ...")
+            return
+        }
+        backgroundMethodChannel.invokeMethod(BackgroundMethods.onLocationUpdate.rawValue, arguments: locationData, result: { flutterResult in
+            CustomLogger.log(message: "Received result: \(flutterResult.debugDescription)")
+        })
+    }
 }
 
 fileprivate enum BackgroundMethods: String {
@@ -53,38 +109,27 @@ extension SwiftBackgroundLocationTrackerPlugin: CLLocationManagerDelegate {
 
         CustomLogger.log(message: "NEW LOCATION: \(location.coordinate.latitude): \(location.coordinate.longitude)")
 
-        guard let callbackHandle = SharedPrefsUtil.getCallbackHandle(),
-              let flutterCallbackInformation = FlutterCallbackCache.lookupCallbackInformation(callbackHandle)
-        else { return }
-
-        var flutterEngine: FlutterEngine? = FlutterEngine(name: flutterThreadLabelPrefix, project: nil, allowHeadlessExecution: true)
-        flutterEngine!.run(withEntrypoint: flutterCallbackInformation.callbackName, libraryURI: flutterCallbackInformation.callbackLibraryPath)
-        SwiftBackgroundLocationTrackerPlugin.flutterPluginRegistrantCallback?(flutterEngine!)
-
-        var backgroundMethodChannel: FlutterMethodChannel? = FlutterMethodChannel(name: SwiftBackgroundLocationTrackerPlugin.BACKGROUND_CHANNEL_NAME, binaryMessenger: flutterEngine!.binaryMessenger)
-
-
-        func cleanupFlutterResources() {
-            flutterEngine?.destroyContext()
-            backgroundMethodChannel = nil
-            flutterEngine = nil
-        }
+        let locationData: [String: Any] = [
+            "lat": location.coordinate.latitude,
+            "lon": location.coordinate.longitude,
+            "logging_enabled": SharedPrefsUtil.isLoggingEnabled(),
+        ]
 
-        backgroundMethodChannel?.setMethodCallHandler { (call, result) in
-            switch call.method {
-            case BackgroundMethods.initialized.rawValue:
-                result(true)
-                let locationData :[String: Any] = [
-                    "lat": location.coordinate.latitude,
-                    "lon": location.coordinate.longitude,
-                    "logging_enabled": SharedPrefsUtil.isLoggingEnabled(),
-                ]
-                backgroundMethodChannel?.invokeMethod(BackgroundMethods.onLocationUpdate.rawValue, arguments: locationData, result: { flutterResult in
-                    cleanupFlutterResources()
-                })
-            default:
-                cleanupFlutterResources()
-                result(FlutterMethodNotImplemented)
+        if (SwiftBackgroundLocationTrackerPlugin.initializedBackgroundCallbacks) {
+            CustomLogger.log(message: "INITIALIZED, ready to send location updates")
+            SwiftBackgroundLocationTrackerPlugin.sendLocationupdate(locationData: locationData)
+        } else {
+            CustomLogger.log(message: "NOT YET INITIALIZED. Cache the location data")
+            SwiftBackgroundLocationTrackerPlugin.locationData = locationData
+
+            if (!SwiftBackgroundLocationTrackerPlugin.initializedBackgroundCallbacksStarted){
+                SwiftBackgroundLocationTrackerPlugin.initializedBackgroundCallbacksStarted = true
+
+                guard let flutterEngine = SwiftBackgroundLocationTrackerPlugin.getFlutterEngine() else {
+                    CustomLogger.log(message: "No Flutter engine available ...")
+                    return
+                }
+                SwiftBackgroundLocationTrackerPlugin.initBackgroundMethodChannel(flutterEngine: flutterEngine)
             }
         }
     }