Implemented null safety

Author: VolkerLieber

binding/flutter/lib/rhino.dart

@@ -22,9 +22,9 @@ import 'package:rhino/rhino_error.dart';
 
 class Rhino {
   static bool _resourcesExtracted = false;
-  static String _defaultModelPath;
+  static String? _defaultModelPath;
 
-  int _handle;
+  int? _handle;
   final String _contextInfo;
   final Pointer<Int16> _cFrame;
 
@@ -56,7 +56,7 @@ class Rhino {
   ///
   /// returns an instance of the speech-to-intent engine
   static Future<Rhino> create(String contextPath,
-      {String modelPath, double sensitivity = 0.5}) async {
+      {String? modelPath, double sensitivity = 0.5}) async {
     if (!_resourcesExtracted) {
       await _extractRhinoResources();
       _resourcesExtracted = true;
@@ -66,6 +66,9 @@ class Rhino {
       throw new PvArgumentError("No context file provided.");
     }
 
+    if (modelPath == null && _defaultModelPath == null) {
+      throw new PvError("No model file provided and default model file not available.");
+    }
     modelPath ??= _defaultModelPath;
 
     if (sensitivity < 0 || sensitivity > 1 || sensitivity.isNaN) {
@@ -74,7 +77,7 @@ class Rhino {
     }
 
     // generate arguments for ffi
-    Pointer<Utf8> cModelPath = modelPath.toNativeUtf8();
+    Pointer<Utf8> cModelPath = modelPath!.toNativeUtf8();
     Pointer<Utf8> cContextPath = contextPath.toNativeUtf8();
     Pointer<IntPtr> handlePtr = malloc<IntPtr>(1);
 
@@ -112,7 +115,7 @@ class Rhino {
   ///   - isUnderstood: if isFinalized, whether Rhino understood what it heard based on the context
   ///   - intent: if isUnderstood, name of intent that were inferred
   ///   - slots: if isUnderstood, dictionary of slot keys and values that were inferred
-  Map<String, dynamic> process(List<int> frame) {
+  Map<String, dynamic> process(List<int>? frame) {
     if (_handle == null) {
       throw new PvStateError(
           "Attempted to process an audio frame after Rhino was been deleted.");
@@ -132,7 +135,7 @@ class Rhino {
     _cFrame.asTypedList(frame.length).setAll(0, frame);
     Pointer<Uint8> isFinalized = malloc(1);
 
-    int status = _rhinoProcess(_handle, _cFrame, isFinalized);
+    int status = _rhinoProcess(_handle!, _cFrame, isFinalized);
     PvStatus pvStatus = PvStatus.values[status];
     if (pvStatus != PvStatus.SUCCESS) {
       pvStatusToException(pvStatus, "Rhino failed to process an audio frame.");
@@ -147,7 +150,7 @@ class Rhino {
 
     // get isUnderstood
     Pointer<Uint8> isUnderstood = malloc(1);
-    status = _rhinoIsUnderstood(_handle, isUnderstood);
+    status = _rhinoIsUnderstood(_handle!, isUnderstood);
     pvStatus = PvStatus.values[status];
     if (pvStatus != PvStatus.SUCCESS) {
       pvStatusToException(pvStatus, "Rhino failed to get IsUnderstood value.");
@@ -161,7 +164,7 @@ class Rhino {
       Pointer<Int32> cNumSlots = malloc(1);
       Pointer<Pointer<Pointer<Utf8>>> cSlots = malloc(1);
       Pointer<Pointer<Pointer<Utf8>>> cValues = malloc(1);
-      status = _rhinoGetIntent(_handle, cIntent, cNumSlots, cSlots, cValues);
+      status = _rhinoGetIntent(_handle!, cIntent, cNumSlots, cSlots, cValues);
       pvStatus = PvStatus.values[status];
       if (pvStatus != PvStatus.SUCCESS) {
         pvStatusToException(pvStatus, "Rhino failed to get intent.");
@@ -178,7 +181,7 @@ class Rhino {
       inference['slots'] = slots;
 
       // free slots
-      status = _rhinoFreeSlotsAndValues(_handle, cSlots[0], cValues[0]);
+      status = _rhinoFreeSlotsAndValues(_handle!, cSlots[0], cValues[0]);
       pvStatus = PvStatus.values[status];
       if (pvStatus != PvStatus.SUCCESS) {
         pvStatusToException(pvStatus, "Rhino failed to free slots.");
@@ -188,7 +191,7 @@ class Rhino {
     }
 
     // reset Rhino
-    status = _rhinoReset(_handle);
+    status = _rhinoReset(_handle!);
     pvStatus = PvStatus.values[status];
     if (pvStatus != PvStatus.SUCCESS) {
       pvStatusToException(pvStatus, "Rhino failed to reset.");
@@ -200,7 +203,7 @@ class Rhino {
   /// Frees memory that was allocated for Rhino
   void delete() {
     if (_handle != null) {
-      _rhinoDelete(_handle);
+      _rhinoDelete(_handle!);
       _handle = null;
     }
   }

binding/flutter/lib/rhino_error.dart

@@ -10,12 +10,12 @@
 //
 
 class PvAudioException implements Exception {
-  final String message;
+  final String? message;
   PvAudioException([this.message]);
 }
 
 class PvError extends Error {
-  final String message;
+  final String? message;
   PvError([this.message]);
 }
 

binding/flutter/lib/rhino_manager.dart

@@ -23,11 +23,11 @@ typedef InferenceCallback(Map<String, dynamic> inference);
 typedef ErrorCallback(PvError error);
 
 class RhinoManager {
-  VoiceProcessor _voiceProcessor;
-  Rhino _rhino;
+  VoiceProcessor? _voiceProcessor;
+  Rhino? _rhino;
 
   final InferenceCallback _inferenceCallback;
-  RemoveListener _removeVoiceProcessorListener;
+  RemoveListener? _removeVoiceProcessorListener;
 
   bool _awaitingStop = false;
 
@@ -49,20 +49,23 @@ class RhinoManager {
   /// returns an instance of the speech-to-intent engine
   static Future<RhinoManager> create(
       String contextPath, InferenceCallback inferenceCallback,
-      {String modelPath,
+      {String? modelPath,
       double sensitivity = 0.5,
-      ErrorCallback errorCallback}) async {
+      ErrorCallback? errorCallback}) async {
     Rhino rhino = await Rhino.create(contextPath,
         modelPath: modelPath, sensitivity: sensitivity);
     return new RhinoManager._(rhino, inferenceCallback, errorCallback);
   }
 
   // private constructor
   RhinoManager._(
-      this._rhino, this._inferenceCallback, ErrorCallback errorCallback)
+      this._rhino, this._inferenceCallback, ErrorCallback? errorCallback)
       : _voiceProcessor = VoiceProcessor.getVoiceProcessor(
             Rhino.frameLength, Rhino.sampleRate) {
-    _removeVoiceProcessorListener = _voiceProcessor.addListener((buffer) async {
+    if (_voiceProcessor == null) {
+      throw new PvError("flutter_voice_processor not available.");
+    }
+    _removeVoiceProcessorListener = _voiceProcessor!.addListener((buffer) async {
       if (_awaitingStop) {
         return;
       }
@@ -82,15 +85,15 @@ class RhinoManager {
 
       // process frame with Rhino
       try {
-        Map<String, dynamic> rhinoResult = _rhino.process(rhinoFrame);
-        if (rhinoResult['isFinalized']) {
+        Map<String, dynamic>? rhinoResult = _rhino?.process(rhinoFrame);
+        if (rhinoResult?['isFinalized']) {
           _awaitingStop = true;
 
           // send inference minus isFinalized
-          rhinoResult.remove('isFinalized');
+          rhinoResult!.remove('isFinalized');
           _inferenceCallback(rhinoResult);
           // stop audio processing
-          await _voiceProcessor.stop();
+          await _voiceProcessor?.stop();
         }
       } on PvError catch (error) {
         errorCallback == null ? print(error.message) : errorCallback(error);
@@ -109,9 +112,9 @@ class RhinoManager {
           "Cannot start RhinoManager - resources have already been released");
     }
 
-    if (await _voiceProcessor.hasRecordAudioPermission()) {
+    if (await _voiceProcessor?.hasRecordAudioPermission() == true) {
       try {
-        await _voiceProcessor.start();
+        await _voiceProcessor!.start();
       } on PlatformException {
         throw new PvAudioException(
             "Audio engine failed to start. Hardware may not be supported.");
@@ -125,15 +128,15 @@ class RhinoManager {
   /// Releases Rhino and audio resouces
   void delete() async {
     if (_voiceProcessor != null) {
-      if (_voiceProcessor.isRecording) {
-        await _voiceProcessor.stop();
+      if (_voiceProcessor!.isRecording) {
+        await _voiceProcessor!.stop();
       }
       _removeVoiceProcessorListener?.call();
       _voiceProcessor = null;
     }
 
     if (_rhino != null) {
-      _rhino.delete();
+      _rhino!.delete();
       _rhino = null;
     }
   }

binding/flutter/pubspec.yaml

@@ -4,7 +4,7 @@ version: 1.6.6
 homepage: https://picovoice.ai/
 
 environment:
-  sdk: ">=2.7.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
   flutter: ">=1.20.0"
 
 dependencies:

demo/flutter/lib/main.dart

@@ -34,7 +34,7 @@ class _MyAppState extends State<MyApp> {
   bool isButtonDisabled = false;
   bool isProcessing = false;
   String rhinoText = "";
-  RhinoManager _rhinoManager;
+  RhinoManager? _rhinoManager;
 
   @override
   void initState() {
@@ -121,7 +121,10 @@ class _MyAppState extends State<MyApp> {
     });
 
     try {
-      await _rhinoManager.process();
+      if (_rhinoManager == null) {
+        throw PvAudioException("_rhinoManager not initialized.");
+      }
+      await _rhinoManager!.process();
       this.setState(() {
         isProcessing = true;
         rhinoText = "Listening...";

demo/flutter/pubspec.yaml

@@ -4,7 +4,7 @@ description: Demonstrates how to use the rhino plugin.
 publish_to: 'none'
 
 environment:
-  sdk: ">=2.7.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
   flutter: