Apply Flutter best practices [Non-Breaking] (#2)

* Add flutter_lints package

* Use key in widget constructors

lint: use_key_in_widget_constructors

* Unnecessary new keyword

lint: unnecessary_new

* Prefer const with constant constructors

* Exclude protobuf files from analyzer

* Private field could be final

* Annotate overridden members

* Use initializing formals when possible

* Don't access members with `this` unless avoiding shadowing

* Prefer is! operator

* Use isEmpty instead of length

* Use collection literals when possible

* Revert comment changes

* Cleaner null testing

* Misc fixes

* Avoid using `forEach` with a function literal

* Prefer `final` over `var` where applicable

* Enforce stricter type-checking

* Ignore VS Code files

* Flutter format

* Prefer using lowerCamelCase for constant names

* flutter format -l 100

* Disable `avoid_print` for examples

* Slight improvements to example

Should solve lint error: no_logic_in_create_state

lib/src/track/_audio_html.dart

@@ -9,10 +9,10 @@ const audioContainerId = 'livekit_audio_container';
 const audioPrefix = 'livekit_audio_';
 
 void startAudio(String id, MediaStreamTrack track) {
-  if (!(track is MediaStreamTrackWeb)) {
+  if (track is! MediaStreamTrackWeb) {
     return;
   }
-  var elementId = audioPrefix + id;
+  final elementId = audioPrefix + id;
   var audioElement = html.document.getElementById(elementId);
   if (audioElement == null) {
     audioElement = html.AudioElement()
@@ -21,16 +21,16 @@ void startAudio(String id, MediaStreamTrack track) {
     findOrCreateAudioContainer().append(audioElement);
   }
 
-  if (!(audioElement is html.AudioElement)) {
+  if (audioElement is! html.AudioElement) {
     return;
   }
-  var audioStream = html.MediaStream();
+  final audioStream = html.MediaStream();
   audioStream.addTrack(track.jsTrack);
   audioElement.srcObject = audioStream;
 }
 
 void stopAudio(String id) {
-  var audioElement = html.document.getElementById(audioPrefix + id);
+  final audioElement = html.document.getElementById(audioPrefix + id);
   if (audioElement != null) {
     if (audioElement is html.AudioElement) {
       audioElement.srcObject = null;

lib/src/track/audio_track.dart

@@ -13,14 +13,14 @@ class AudioTrack extends Track {
 
   /// Start playing audio track. On web platform, create an audio element and
   /// start playback
-  start() {
-    if (!(this is LocalAudioTrack)) {
+  void start() {
+    if (this is! LocalAudioTrack) {
       audio.startAudio(getCid(), mediaTrack);
     }
   }
 
   @override
-  stop() {
+  void stop() {
     mediaStream?.dispose();
     mediaStream = null;
     audio.stopAudio(getCid());

lib/src/track/local_audio_track.dart

@@ -9,19 +9,18 @@ class LocalAudioTrack extends AudioTrack {
       : super(name, track, stream);
 
   /// Creates a new audio track from the default audio input device.
-  static Future<LocalAudioTrack> createTrack(
-      [LocalAudioTrackOptions? options]) async {
+  static Future<LocalAudioTrack> createTrack([LocalAudioTrackOptions? options]) async {
     try {
-      var stream = await navigator.mediaDevices.getUserMedia({
-        "audio": true,
-        "video": false,
+      final stream = await navigator.mediaDevices.getUserMedia(<String, dynamic>{
+        'audio': true,
+        'video': false,
       });
 
-      if (stream.getAudioTracks().length == 0) {
+      if (stream.getAudioTracks().isEmpty) {
         return Future.error(TrackCreateError());
       }
 
-      return LocalAudioTrack("", stream.getAudioTracks().first, stream);
+      return LocalAudioTrack('', stream.getAudioTracks().first, stream);
     } catch (e) {
       return Future.error(e);
     }

lib/src/track/local_track_publication.dart

@@ -4,14 +4,14 @@ import 'track.dart';
 import 'track_publication.dart';
 
 class LocalTrackPublication extends TrackPublication {
-  LocalParticipant _participant;
+  final LocalParticipant _participant;
 
-  LocalTrackPublication(TrackInfo info, Track track, this._participant)
-      : super.fromInfo(info) {
+  LocalTrackPublication(TrackInfo info, Track track, this._participant) : super.fromInfo(info) {
     this.track = track;
   }
 
   /// Mute or unmute the current track. When muted, track will stop sending data
+  @override
   set muted(bool val) {
     if (val == muted) {
       return;

lib/src/track/local_video_track.dart

@@ -13,15 +13,12 @@ class LocalVideoTrack extends VideoTrack {
       : super(name, mediaTrack, stream);
 
   /// Creates a LocalVideoTrack from camera input.
-  static Future<LocalVideoTrack> createCameraTrack(
-      [LocalVideoTrackOptions? options]) async {
-    if (options == null) {
-      options = LocalVideoTrackOptions(params: VideoPresets.qhd);
-    }
+  static Future<LocalVideoTrack> createCameraTrack([LocalVideoTrackOptions? options]) async {
+    options ??= LocalVideoTrackOptions(params: VideoPresets.qhd);
 
     try {
-      var stream = await _createCameraStream(options);
-      return LocalVideoTrack("camera", stream.getVideoTracks().first, stream);
+      final stream = await _createCameraStream(options);
+      return LocalVideoTrack('camera', stream.getVideoTracks().first, stream);
     } catch (e) {
       return Future.error(e);
     }
@@ -34,13 +31,11 @@ class LocalVideoTrack extends VideoTrack {
       return Future.error(TrackCreateError('could not restart track'));
     }
 
-    if (options == null) {
-      options = LocalVideoTrackOptions(params: VideoPresets.qhd);
-    }
+    options ??= LocalVideoTrackOptions(params: VideoPresets.qhd);
 
     try {
-      var stream = await _createCameraStream(options);
-      var track = stream.getVideoTracks().first;
+      final stream = await _createCameraStream(options);
+      final track = stream.getVideoTracks().first;
       mediaStream = stream;
       await mediaTrack.stop();
       mediaTrack = track;
@@ -50,19 +45,16 @@ class LocalVideoTrack extends VideoTrack {
     }
   }
 
-  static Future<MediaStream> _createCameraStream(
-      LocalVideoTrackOptions? options) async {
-    if (options == null) {
-      options = LocalVideoTrackOptions(params: VideoPresets.qhd);
-    }
+  static Future<MediaStream> _createCameraStream(LocalVideoTrackOptions? options) async {
+    options ??= LocalVideoTrackOptions(params: VideoPresets.qhd);
 
     try {
-      var stream = await navigator.mediaDevices.getUserMedia({
-        "audio": false,
-        "video": options.mediaConstraints,
+      final stream = await navigator.mediaDevices.getUserMedia(<String, dynamic>{
+        'audio': false,
+        'video': options.mediaConstraints,
       });
 
-      if (stream.getVideoTracks().length == 0) {
+      if (stream.getVideoTracks().isEmpty) {
         return Future.error(TrackCreateError());
       }
 

lib/src/track/options.dart

@@ -1,6 +1,6 @@
 /// Options when creating a LocalVideoTrack.
 class LocalVideoTrackOptions {
-  CameraPosition position = CameraPosition.FRONT;
+  CameraPosition position = CameraPosition.front;
   VideoParameter params;
 
   LocalVideoTrackOptions({
@@ -16,16 +16,16 @@ class LocalVideoTrackOptions {
   }
 
   Map<String, dynamic> get mediaConstraints {
-    return {
-      "mandatory": params.mediaConstraints,
-      "facingMode": position == CameraPosition.FRONT ? "user" : "environment",
+    return <String, dynamic>{
+      'mandatory': params.mediaConstraints,
+      'facingMode': position == CameraPosition.front ? 'user' : 'environment',
     };
   }
 }
 
 enum CameraPosition {
-  FRONT,
-  BACK,
+  front,
+  back,
 }
 
 class VideoParameter {
@@ -38,14 +38,14 @@ class VideoParameter {
     this.width,
     this.height,
     this.fps, {
-    int? bitrate,
-  }) : this.bitrate = bitrate;
+    this.bitrate,
+  });
 
   Map<String, dynamic> get mediaConstraints {
-    return {
-      "minWidth": this.width,
-      "minHeight": this.height,
-      "minFrameRate": this.fps,
+    return <String, dynamic>{
+      'minWidth': width,
+      'minHeight': height,
+      'minFrameRate': fps,
     };
   }
 }

lib/src/track/remote_track_publication.dart

@@ -7,7 +7,7 @@ import 'track_publication.dart';
 /// Represents a track publication from a RemoteParticipant. Provides methods to
 /// control if we should subscribe to the track, and its quality (for video).
 class RemoteTrackPublication extends TrackPublication {
-  RemoteParticipant _participant;
+  final RemoteParticipant _participant;
   bool _unsubscribed = false;
   bool _disabled = false;
   VideoQuality _videoQuality = VideoQuality.HIGH;
@@ -26,6 +26,7 @@ class RemoteTrackPublication extends TrackPublication {
     _sendUpdateTrackSettings();
   }
 
+  @override
   bool get subscribed {
     if (_unsubscribed) {
       return false;
@@ -41,6 +42,7 @@ class RemoteTrackPublication extends TrackPublication {
 
   /// for internal use
   /// {@nodoc}
+  @override
   set muted(bool val) {
     if (val == muted) {
       return;
@@ -59,13 +61,12 @@ class RemoteTrackPublication extends TrackPublication {
     _participant.muteChanged();
   }
 
-  RemoteTrackPublication(TrackInfo info, this._participant, [Track? track])
-      : super.fromInfo(info) {
+  RemoteTrackPublication(TrackInfo info, this._participant, [Track? track]) : super.fromInfo(info) {
     this.track = track;
   }
 
-  _sendUpdateTrackSettings() {
-    var settings = new UpdateTrackSettings(
+  void _sendUpdateTrackSettings() {
+    final settings = UpdateTrackSettings(
       trackSids: [sid],
       disabled: _disabled,
     );

lib/src/track/track.dart

@@ -12,7 +12,7 @@ class TrackDimension {
 
 /// Wrapper around a MediaStreamTrack with additional metadata.
 class Track {
-  static const ScreenShareName = "screen";
+  static const screenShareName = 'screen';
 
   String name;
   TrackType kind;
@@ -38,19 +38,17 @@ class Track {
   }
 
   String getCid() {
-    var cid = _cid;
+    var cid = _cid ?? mediaTrack.id;
+
     if (cid == null) {
-      cid = mediaTrack.id;
-    }
-    if (cid == null) {
-      var uuid = Uuid();
+      const uuid = Uuid();
       cid = uuid.v4();
       _cid = cid;
     }
     return cid;
   }
 
-  stop() {
+  void stop() {
     mediaTrack.stop();
   }
 }

lib/src/track/track_publication.dart

@@ -21,15 +21,14 @@ class TrackPublication {
     updateFromInfo(info);
   }
 
-  /// True when the track is published with name [Track.ScreenShareName].
-  bool get isScreenShare =>
-      kind == TrackType.VIDEO && name == Track.ScreenShareName;
+  /// True when the track is published with name [Track.screenShareName].
+  bool get isScreenShare => kind == TrackType.VIDEO && name == Track.screenShareName;
 
-  updateFromInfo(TrackInfo info) {
+  void updateFromInfo(TrackInfo info) {
     muted = info.muted;
     simulcasted = info.simulcast;
     if (info.type == TrackType.VIDEO) {
-      dimension = new TrackDimension(info.width, info.height);
+      dimension = TrackDimension(info.width, info.height);
     }
   }
 }