Fix lack of lifecycle management in TextToSpeech on iOS

Change-Id: Ib8732739e437f3aa32f6203589cc9e6e9fb30228

appinventor/aicompanionapp/src/ViewController.swift

@@ -72,6 +72,7 @@ public class ViewController: UINavigationController, UITextFieldDelegate {
     SCMInterpreter.shared.protect(self)
     ViewController.controller = self
     NotificationCenter.default.addObserver(self, selector: #selector(settingsChanged(_:)), name: UserDefaults.didChangeNotification, object: nil)
+    self.delegate = self
   }
 
   @objc func settingsChanged(_ sender: AnyObject?) {
@@ -386,3 +387,20 @@ public class ViewController: UINavigationController, UITextFieldDelegate {
     }
   }
 }
+
+extension ViewController: UINavigationControllerDelegate {
+  public func navigationController(_ navigationController: UINavigationController,
+      animationControllerFor operation: UINavigationController.Operation,
+      from fromVC: UIViewController,
+      to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
+    guard let oldForm = fromVC as? Form, let newForm = toVC as? Form else {
+      return nil
+    }
+    oldForm.onPause()
+    if operation == .pop {
+      oldForm.onDestroy()
+    }
+    newForm.onResume()
+    return nil
+  }
+}

appinventor/components-ios/src/Form.swift

@@ -167,6 +167,10 @@ let kMinimumToastWait = 10.0
     view.accessibilityIdentifier = String(describing: type(of: self))
   }
 
+  open func add(_ component: NonvisibleComponent) {
+    _components.append(component)
+  }
+
   open func add(_ component: ViewComponent) {
     _components.append(component)
     _linearView.addItem(LinearViewItem(component.view))

appinventor/components-ios/src/NonvisibleComponent.swift

@@ -10,6 +10,8 @@ open class NonvisibleComponent: NSObject, Component {
 
   @objc public init(_ container: ComponentContainer) {
     self._form = container.form
+    super.init()
+    _form?.add(self)
   }
 
   open func copy(with zone: NSZone? = nil) -> Any {

appinventor/components-ios/src/TextToSpeech.swift

@@ -163,15 +163,17 @@ open class TextToSpeech: NonvisibleComponent, AVSpeechSynthesizerDelegate {
   // MARK: Methods
 
   @objc open func Speak(_ message: String) throws {
-    BeforeSpeaking()
     try AVAudioSession.sharedInstance().setCategory(AVAudioSession.Category.playback)
     try AVAudioSession.sharedInstance().setActive(true)
-    let utterance = AVSpeechUtterance(string: message)
-    utterance.pitchMultiplier = _pitch
-    utterance.rate = _speechRate
-    utterance.voice = _voice
-    _tts.stopSpeaking(at: AVSpeechBoundary.immediate)
-    _tts.speak(utterance)
+    DispatchQueue.main.async {
+      self.BeforeSpeaking()
+      let utterance = AVSpeechUtterance(string: message)
+      utterance.pitchMultiplier = self._pitch
+      utterance.rate = self._speechRate
+      utterance.voice = self._voice
+      self._tts.stopSpeaking(at: AVSpeechBoundary.immediate)
+      self._tts.speak(utterance)
+    }
   }
 
   @objc open func Stop() {
@@ -214,3 +216,23 @@ open class TextToSpeech: NonvisibleComponent, AVSpeechSynthesizerDelegate {
     }
   }
 }
+
+extension TextToSpeech: LifecycleDelegate {
+  public func onResume() {
+    if _tts.isPaused {
+      _tts.continueSpeaking()
+    }
+  }
+
+  public func onPause() {
+    _tts.pauseSpeaking(at: .immediate)
+  }
+
+  public func onDestroy() {
+    Stop()
+  }
+
+  public func onDelete() {
+    Stop()
+  }
+}