refactor: let EventStreamHandler create channel

Author: ddfreiling

flutter_readium/ios/flutter_readium/Sources/flutter_readium/EventStreamHandler.swift

@@ -2,6 +2,11 @@ import Flutter
 
 class EventStreamHandler: NSObject, FlutterStreamHandler {
 
+  private let TAG: String
+  private let streamName: String
+  private var channel: FlutterEventChannel
+  private var eventSink: FlutterEventSink?
+
   public func sendEvent(_ event: Any?) {
     print(TAG, "sendEvent")
     eventSink?(event)
@@ -19,12 +24,20 @@ class EventStreamHandler: NSObject, FlutterStreamHandler {
     return nil
   }
 
-  var eventSink: FlutterEventSink?
-  var streamName: String
-  let TAG: String
+  func dispose() {
+    print(TAG, "dispose")
+    // End stream and clear the event-sink to prevent memory leaks.
+    eventSink?(FlutterEndOfEventStream)
+    eventSink = nil
+    channel.setStreamHandler(nil)
+  }
 
-  init(streamName: String) {
+  init(withName streamName: String, messenger: FlutterBinaryMessenger) {
     self.streamName = streamName
-    self.TAG = "EventStreamHandler[\(streamName)]"
+    TAG = "EventStreamHandler[\(streamName)]"
+    channel = FlutterEventChannel(name: "dk.nota.flutter_readium/\(streamName)", binaryMessenger: messenger)
+    super.init()
+
+    channel.setStreamHandler(self)
   }
 }

flutter_readium/ios/flutter_readium/Sources/flutter_readium/FlutterReadiumPlugin.swift

@@ -21,17 +21,16 @@ func setCurrentReadiumReaderView(_ readerView: ReadiumReaderView?) {
 public class FlutterReadiumPlugin: NSObject, FlutterPlugin, ReadiumShared.WarningLogger {
   static var registrar: FlutterPluginRegistrar? = nil
 
-  
+
   /// TTS related variables
   /// TODO: Refactor into a TTSViewModel?
   @Published internal var playingUtterance: Locator?
   internal let playingWordRangeSubject = PassthroughSubject<Locator, Never>()
   internal var subscriptions: Set<AnyCancellable> = []
   internal var isMoving = false
-  
-  internal static var audioLocatorChannel: FlutterEventChannel?
+
   internal var audioLocatorStreamHandler: EventStreamHandler?
-  
+
   internal var synthesizer: PublicationSpeechSynthesizer? = nil
   internal var ttsPrefs: TTSPreferences? = nil
 
@@ -43,8 +42,7 @@ public class FlutterReadiumPlugin: NSObject, FlutterPlugin, ReadiumShared.Warnin
     let channel = FlutterMethodChannel(name: "dk.nota.flutter_readium/main", binaryMessenger: registrar.messenger())
     let instance = FlutterReadiumPlugin()
     registrar.addMethodCallDelegate(instance, channel: channel)
-    
-    audioLocatorChannel = FlutterEventChannel(name: "dk.nota.flutter_readium/audio-locator", binaryMessenger: registrar.messenger())
+    instance.audioLocatorStreamHandler = EventStreamHandler(withName: "audio-locator", messenger: registrar.messenger())
 
     // Register reader view factory
     let factory = ReadiumReaderViewFactory(registrar: registrar)
@@ -53,12 +51,6 @@ public class FlutterReadiumPlugin: NSObject, FlutterPlugin, ReadiumShared.Warnin
     self.registrar = registrar
   }
 
-  public override init() {
-    super.init()
-    audioLocatorStreamHandler = EventStreamHandler(streamName: "audio-locator")
-    FlutterReadiumPlugin.audioLocatorChannel?.setStreamHandler(audioLocatorStreamHandler)
-  }
-
   public func log(_ warning: Warning) {
     print(TAG, "Error in Readium: \(warning)")
   }
@@ -74,6 +66,8 @@ public class FlutterReadiumPlugin: NSObject, FlutterPlugin, ReadiumShared.Warnin
       }
       self.synthesizer?.stop()
       self.synthesizer = nil
+      self.audioLocatorStreamHandler?.dispose()
+      self.audioLocatorStreamHandler = nil
       result(nil)
     case "closePublication":
       let pubId = call.arguments as! String

flutter_readium/ios/flutter_readium/Sources/flutter_readium/ReadiumReaderView.swift

@@ -22,7 +22,6 @@ private var userScripts: [WKUserScript] = []
 class ReadiumReaderView: NSObject, FlutterPlatformView, EPUBNavigatorDelegate {
 
   private let channel: ReadiumReaderChannel
-  private let textLocatorChannel: FlutterEventChannel
   private var textLocatorStreamHandler: EventStreamHandler?
   private let _view: UIView
   private let readiumViewController: EPUBNavigatorViewController
@@ -39,8 +38,9 @@ class ReadiumReaderView: NSObject, FlutterPlatformView, EPUBNavigatorDelegate {
     print(TAG, "::dispose")
     readiumViewController.view.removeFromSuperview()
     readiumViewController.delegate = nil
+    textLocatorStreamHandler?.dispose()
+    textLocatorStreamHandler = nil
     channel.setMethodCallHandler(nil)
-    textLocatorChannel.setStreamHandler(nil)
     setCurrentReadiumReaderView(nil)
   }
 
@@ -65,7 +65,7 @@ class ReadiumReaderView: NSObject, FlutterPlatformView, EPUBNavigatorDelegate {
 
     channel = ReadiumReaderChannel(
       name: "\(readiumReaderViewType):\(viewId)", binaryMessenger: registrar.messenger())
-    textLocatorChannel = FlutterEventChannel(name: "dk.nota.flutter_readium/text-locator", binaryMessenger: registrar.messenger())
+    textLocatorStreamHandler = EventStreamHandler(withName: "text-locator", messenger: registrar.messenger())
 
     print(TAG, "Publication: (identifier=\(String(describing: publication.metadata.identifier)),title=\(String(describing: publication.metadata.title)))")
     print(TAG, "Added publication at \(String(describing: publication.baseURL))")
@@ -100,8 +100,6 @@ class ReadiumReaderView: NSObject, FlutterPlatformView, EPUBNavigatorDelegate {
     super.init()
 
     channel.setMethodCallHandler(onMethodCall)
-    textLocatorStreamHandler = EventStreamHandler(streamName: "text-locator")
-    textLocatorChannel.setStreamHandler(textLocatorStreamHandler)
     readiumViewController.delegate = self
 
     let child: UIView = readiumViewController.view  // Must specify type `UIView`, or we end up with an `UIView?` instead…