prefer_final_fields (#8967)

examples/flutter_gallery/lib/demo/material/data_table_demo.dart

@@ -151,7 +151,7 @@ class _DataTableDemoState extends State<DataTableDemo> {
   int _rowsPerPage = PaginatedDataTable.defaultRowsPerPage;
   int _sortColumnIndex;
   bool _sortAscending = true;
-  DessertDataSource _dessertsDataSource = new DessertDataSource();
+  final DessertDataSource _dessertsDataSource = new DessertDataSource();
 
   void _sort<T>(Comparable<T> getField(Dessert d), int columnIndex, bool ascending) {
     _dessertsDataSource._sort<T>(getField, ascending);

examples/flutter_gallery/lib/demo/material/date_and_time_picker_demo.dart

@@ -121,7 +121,7 @@ class _DateAndTimePickerDemoState extends State<DateAndTimePickerDemo> {
   TimeOfDay _fromTime = const TimeOfDay(hour: 7, minute: 28);
   DateTime _toDate = new DateTime.now();
   TimeOfDay _toTime = const TimeOfDay(hour: 7, minute: 28);
-  List<String> _allActivities = <String>['hiking', 'swimming', 'boating', 'fishing'];
+  final List<String> _allActivities = <String>['hiking', 'swimming', 'boating', 'fishing'];
   String _activity = 'fishing';
 
   @override

examples/flutter_gallery/lib/demo/material/text_field_demo.dart

@@ -34,8 +34,8 @@ class TextFieldDemoState extends State<TextFieldDemo> {
 
   bool _autovalidate = false;
   bool _formWasEdited = false;
-  GlobalKey<FormState> _formKey = new GlobalKey<FormState>();
-  GlobalKey<FormFieldState<InputValue>> _passwordFieldKey = new GlobalKey<FormFieldState<InputValue>>();
+  final GlobalKey<FormState> _formKey = new GlobalKey<FormState>();
+  final GlobalKey<FormFieldState<InputValue>> _passwordFieldKey = new GlobalKey<FormFieldState<InputValue>>();
   void _handleSubmitted() {
     final FormState form = _formKey.currentState;
     if (!form.validate()) {

packages/flutter/lib/src/gestures/binding.dart

@@ -61,7 +61,7 @@ abstract class GestureBinding extends BindingBase implements HitTestable, HitTes
   ///
   /// The state of hovering pointers is not tracked because that would require
   /// hit-testing on every frame.
-  Map<int, HitTestResult> _hitTests = <int, HitTestResult>{};
+  final Map<int, HitTestResult> _hitTests = <int, HitTestResult>{};
 
   void _handlePointerEvent(PointerEvent event) {
     HitTestResult result;

packages/flutter/lib/src/gestures/converter.dart

@@ -34,7 +34,7 @@ class _PointerState {
 /// Converts from engine pointer data to framework pointer events.
 class PointerEventConverter {
   // Map from platform pointer identifiers to PointerEvent pointer identifiers.
-  static Map<int, _PointerState> _pointers = <int, _PointerState>{};
+  static final Map<int, _PointerState> _pointers = <int, _PointerState>{};
 
   static _PointerState _ensureStateForPointer(ui.PointerData datum, Point position) {
     return _pointers.putIfAbsent(

packages/flutter/lib/src/gestures/drag.dart

@@ -278,7 +278,7 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
   double _getPrimaryValueFromOffset(Offset value);
   bool get _hasSufficientPendingDragDeltaToAccept;
 
-  Map<int, VelocityTracker> _velocityTrackers = <int, VelocityTracker>{};
+  final Map<int, VelocityTracker> _velocityTrackers = <int, VelocityTracker>{};
 
   @override
   void addPointer(PointerEvent event) {

packages/flutter/lib/src/gestures/scale.dart

@@ -115,7 +115,7 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
   double _initialSpan;
   double _currentSpan;
   Map<int, Point> _pointerLocations;
-  Map<int, VelocityTracker> _velocityTrackers = <int, VelocityTracker>{};
+  final Map<int, VelocityTracker> _velocityTrackers = <int, VelocityTracker>{};
 
   double get _scaleFactor => _initialSpan > 0.0 ? _currentSpan / _initialSpan : 1.0;
 

packages/flutter/lib/src/material/about.dart

@@ -369,7 +369,7 @@ class _LicensePageState extends State<LicensePage> {
     _initLicenses();
   }
 
-  List<Widget> _licenses = <Widget>[];
+  final List<Widget> _licenses = <Widget>[];
   bool _loaded = false;
 
   Future<Null> _initLicenses() async {

packages/flutter/lib/src/material/date_picker.dart

@@ -599,7 +599,7 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
 
   DateTime _selectedDate;
   _DatePickerMode _mode = _DatePickerMode.day;
-  GlobalKey _pickerKey = new GlobalKey();
+  final GlobalKey _pickerKey = new GlobalKey();
 
   void _vibrate() {
     switch (Theme.of(context).platform) {

packages/flutter/lib/src/material/input.dart

@@ -107,8 +107,8 @@ class InputField extends StatefulWidget {
 }
 
 class _InputFieldState extends State<InputField> {
-  GlobalKey<EditableTextState> _editableTextKey = new GlobalKey<EditableTextState>();
-  GlobalKey<EditableTextState> _focusKey = new GlobalKey(debugLabel: "_InputFieldState _focusKey");
+  final GlobalKey<EditableTextState> _editableTextKey = new GlobalKey<EditableTextState>();
+  final GlobalKey<EditableTextState> _focusKey = new GlobalKey(debugLabel: "_InputFieldState _focusKey");
 
   GlobalKey get focusKey => config.focusKey ?? (config.key is GlobalKey ? config.key : _focusKey);
 

packages/flutter/lib/src/material/progress_indicator.dart

@@ -455,7 +455,7 @@ class RefreshProgressIndicator extends CircularProgressIndicator {
 }
 
 class _RefreshProgressIndicatorState extends _CircularProgressIndicatorState {
-  static double _kIndicatorSize = 40.0;
+  static const double _kIndicatorSize = 40.0;
 
   // Always show the indeterminate version of the circular progress indicator.
   // When value is non-null the sweep of the progress indicator arrow's arc

packages/flutter/lib/src/material/scaffold.dart

@@ -512,7 +512,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
 
   // SNACKBAR API
 
-  Queue<ScaffoldFeatureController<SnackBar, SnackBarClosedReason>> _snackBars = new Queue<ScaffoldFeatureController<SnackBar, SnackBarClosedReason>>();
+  final Queue<ScaffoldFeatureController<SnackBar, SnackBarClosedReason>> _snackBars = new Queue<ScaffoldFeatureController<SnackBar, SnackBarClosedReason>>();
   AnimationController _snackBarController;
   Timer _snackBarTimer;
 

packages/flutter/lib/src/rendering/animated_size.dart

@@ -58,7 +58,7 @@ class RenderAnimatedSize extends RenderAligningShiftedBox {
 
   AnimationController _controller;
   CurvedAnimation _animation;
-  SizeTween _sizeTween = new SizeTween();
+  final SizeTween _sizeTween = new SizeTween();
   bool _didChangeTargetSizeLastFrame = false;
   bool _hasVisualOverflow;
   double _lastValue;

packages/flutter/lib/src/rendering/object.dart

@@ -1020,7 +1020,7 @@ class PipelineOwner {
     }
   }
 
-  List<RenderObject> _nodesNeedingCompositingBitsUpdate = <RenderObject>[];
+  final List<RenderObject> _nodesNeedingCompositingBitsUpdate = <RenderObject>[];
   /// Updates the [needsCompositing] bits.
   ///
   /// Called as part of the rendering pipeline after [flushLayout] and before

packages/flutter/lib/src/rendering/table.dart

@@ -1079,7 +1079,7 @@ class RenderTable extends RenderBox {
   }
 
   // cache the table geometry for painting purposes
-  List<double> _rowTops = <double>[];
+  final List<double> _rowTops = <double>[];
   List<double> _columnLefts;
 
   /// Returns the position and dimensions of the box that the given

packages/flutter/lib/src/widgets/drag_target.dart

@@ -462,7 +462,7 @@ class _DragAvatar<T> extends Drag {
   final OverlayState overlayState;
 
   _DragTargetState<T> _activeTarget;
-  List<_DragTargetState<T>> _enteredTargets = <_DragTargetState<T>>[];
+  final List<_DragTargetState<T>> _enteredTargets = <_DragTargetState<T>>[];
   Point _position;
   Offset _lastOffset;
   OverlayEntry _entry;

packages/flutter/lib/src/widgets/form.dart

@@ -70,7 +70,7 @@ class Form extends StatefulWidget {
 /// Typically obtained via [Form.of].
 class FormState extends State<Form> {
   int _generation = 0;
-  Set<FormFieldState<dynamic>> _fields = new Set<FormFieldState<dynamic>>();
+  final Set<FormFieldState<dynamic>> _fields = new Set<FormFieldState<dynamic>>();
 
   // Called when a form field has changed. This will cause all form fields
   // to rebuild, useful if form fields have interdependencies.

packages/flutter/lib/src/widgets/heroes.dart

@@ -135,7 +135,7 @@ class Hero extends StatefulWidget {
 }
 
 class _HeroState extends State<Hero> {
-  GlobalKey _key = new GlobalKey();
+  final GlobalKey _key = new GlobalKey();
   Size _placeholderSize;
 
   void startFlight() {

packages/flutter/lib/src/widgets/sliver.dart

@@ -287,8 +287,8 @@ class SliverMultiBoxAdaptorElement extends RenderObjectElement implements Render
       performRebuild();
   }
 
-  SplayTreeMap<int, Element> _childElements = new SplayTreeMap<int, Element>();
-  Map<int, Widget> _childWidgets = new HashMap<int, Widget>();
+  final SplayTreeMap<int, Element> _childElements = new SplayTreeMap<int, Element>();
+  final Map<int, Widget> _childWidgets = new HashMap<int, Widget>();
   RenderBox _currentBeforeChild;
 
   @override

packages/flutter/test/widgets/routes_test.dart

@@ -18,7 +18,7 @@ class TestRoute extends LocalHistoryRoute<String> {
   @override
   List<OverlayEntry> get overlayEntries => _entries;
 
-  List<OverlayEntry> _entries = <OverlayEntry>[];
+  final List<OverlayEntry> _entries = <OverlayEntry>[];
 
   void log(String s) {
     results.add('$name: $s');

packages/flutter_test/lib/src/test_async_utils.dart

@@ -48,7 +48,7 @@ class TestAsyncUtils {
   TestAsyncUtils._();
   static const String _className = 'TestAsyncUtils';
 
-  static List<_AsyncScope> _scopeStack = <_AsyncScope>[];
+  static final List<_AsyncScope> _scopeStack = <_AsyncScope>[];
 
   /// Calls the given callback in a new async scope. The callback argument is
   /// the asynchronous body of the calling method. The calling method is said to

packages/flutter_tools/lib/src/android/android_device.dart

@@ -427,7 +427,7 @@ class AndroidDevice extends Device {
     return _portForwarder;
   }
 
-  static RegExp _timeRegExp = new RegExp(r'^\d{2}-\d{2} \d{2}:\d{2}:\d{2}\.\d{3}', multiLine: true);
+  static final RegExp _timeRegExp = new RegExp(r'^\d{2}-\d{2} \d{2}:\d{2}:\d{2}\.\d{3}', multiLine: true);
 
   /// Return the most recent timestamp in the Android log or `null` if there is
   /// no available timestamp. The format can be passed to logcat's -T option.

packages/flutter_tools/lib/src/android/android_studio.dart

@@ -61,7 +61,7 @@ class AndroidStudio implements Comparable<AndroidStudio> {
   String _gradlePath;
   String _javaPath;
   bool _isValid = false;
-  List<String> _validationMessages = <String>[];
+  final List<String> _validationMessages = <String>[];
 
   factory AndroidStudio.fromMacOSBundle(String bundlePath) {
     final String studioPath = fs.path.join(bundlePath, 'Contents');

packages/flutter_tools/lib/src/base/context.dart

@@ -11,7 +11,7 @@ typedef void ErrorHandler(dynamic error, StackTrace stackTrace);
 AppContext get context => Zone.current['context'];
 
 class AppContext {
-  Map<Type, dynamic> _instances = <Type, dynamic>{};
+  final Map<Type, dynamic> _instances = <Type, dynamic>{};
   Zone _zone;
 
   AppContext() : _zone = Zone.current;

packages/flutter_tools/lib/src/base/logger.dart

@@ -135,9 +135,9 @@ class BufferLogger extends Logger {
   @override
   bool get isVerbose => false;
 
-  StringBuffer _error = new StringBuffer();
-  StringBuffer _status = new StringBuffer();
-  StringBuffer _trace = new StringBuffer();
+  final StringBuffer _error = new StringBuffer();
+  final StringBuffer _status = new StringBuffer();
+  final StringBuffer _trace = new StringBuffer();
 
   String get errorText => _error.toString();
   String get statusText => _status.toString();
@@ -282,7 +282,7 @@ class AnsiTerminal {
   String clearScreen() => supportsColor ? _clear : '\n\n';
 
   set singleCharMode(bool value) {
-    // TODO(goderbauer): instead of trying to set lineMode and then catching [_ENOTTY] or [_INVALID_HANDLE], 
+    // TODO(goderbauer): instead of trying to set lineMode and then catching [_ENOTTY] or [_INVALID_HANDLE],
     //     we should check beforehand if stdin is connected to a terminal or not
     //     (requires https://github.com/dart-lang/sdk/issues/29083 to be resolved).
     try {

packages/flutter_tools/lib/src/base/utils.dart

@@ -105,8 +105,8 @@ class ItemListNotifier<T> {
 
   Set<T> _items;
 
-  StreamController<T> _addedController = new StreamController<T>.broadcast();
-  StreamController<T> _removedController = new StreamController<T>.broadcast();
+  final StreamController<T> _addedController = new StreamController<T>.broadcast();
+  final StreamController<T> _removedController = new StreamController<T>.broadcast();
 
   Stream<T> get onAdded => _addedController.stream;
   Stream<T> get onRemoved => _removedController.stream;
@@ -168,7 +168,7 @@ class SettingsFile {
 /// For more information, see
 /// http://en.wikipedia.org/wiki/Universally_unique_identifier.
 class Uuid {
-  Random _random = new Random();
+  final Random _random = new Random();
 
   /// Generate a version 4 (random) uuid. This is a uuid scheme that only uses
   /// random numbers as the source of the generated uuid.

packages/flutter_tools/lib/src/commands/analyze_continuously.dart

@@ -150,8 +150,8 @@ class AnalysisServer {
   final List<String> directories;
 
   Process _process;
-  StreamController<bool> _analyzingController = new StreamController<bool>.broadcast();
-  StreamController<FileAnalysisErrors> _errorsController = new StreamController<FileAnalysisErrors>.broadcast();
+  final StreamController<bool> _analyzingController = new StreamController<bool>.broadcast();
+  final StreamController<FileAnalysisErrors> _errorsController = new StreamController<FileAnalysisErrors>.broadcast();
 
   int _id = 0;
 

packages/flutter_tools/lib/src/commands/daemon.dart

@@ -286,11 +286,11 @@ class AppDomain extends Domain {
     registerHandler('discover', discover);
   }
 
-  static Uuid _uuidGenerator = new Uuid();
+  static final Uuid _uuidGenerator = new Uuid();
 
   static String _getNewAppId() => _uuidGenerator.generateV4();
 
-  List<AppInstance> _apps = <AppInstance>[];
+  final List<AppInstance> _apps = <AppInstance>[];
 
   Future<Map<String, dynamic>> start(Map<String, dynamic> args) async {
     final String deviceId = _getStringArg(args, 'deviceId', required: true);
@@ -537,7 +537,7 @@ class DeviceDomain extends Domain {
     }
   }
 
-  List<PollingDeviceDiscovery> _discoverers = <PollingDeviceDiscovery>[];
+  final List<PollingDeviceDiscovery> _discoverers = <PollingDeviceDiscovery>[];
 
   Future<List<Device>> getDevices([Map<String, dynamic> args]) {
     final List<Device> devices = _discoverers.expand((PollingDeviceDiscovery discoverer) {
@@ -670,7 +670,7 @@ dynamic _toJsonable(dynamic obj) {
 }
 
 class NotifyingLogger extends Logger {
-  StreamController<LogMessage> _messageController = new StreamController<LogMessage>.broadcast();
+  final StreamController<LogMessage> _messageController = new StreamController<LogMessage>.broadcast();
 
   Stream<LogMessage> get onMessage => _messageController.stream;
 

packages/flutter_tools/lib/src/dart/analysis.dart

@@ -34,7 +34,7 @@ class AnalysisDriver {
     _processPlugins();
   }
 
-  Set<Source> _analyzedSources = new HashSet<Source>();
+  final Set<Source> _analyzedSources = new HashSet<Source>();
 
   AnalysisOptionsProvider analysisOptionsProvider =
       new AnalysisOptionsProvider();
@@ -245,7 +245,7 @@ class PackageInfo {
   Packages _packages;
 
   Map<String, List<file_system.Folder>> asMap() => _map;
-  HashMap<String, List<file_system.Folder>> _map =
+  final HashMap<String, List<file_system.Folder>> _map =
       new HashMap<String, List<file_system.Folder>>();
 
   Packages asPackages() => _packages;

packages/flutter_tools/lib/src/device.dart

@@ -30,7 +30,7 @@ class DeviceManager {
     _deviceDiscoverers.add(new IOSSimulators());
   }
 
-  List<DeviceDiscovery> _deviceDiscoverers = <DeviceDiscovery>[];
+  final List<DeviceDiscovery> _deviceDiscoverers = <DeviceDiscovery>[];
 
   /// A user-specified device ID.
   String specifiedDeviceId;

packages/flutter_tools/lib/src/vmservice.dart

@@ -96,7 +96,7 @@ class VMService {
   final Map<String, StreamController<ServiceEvent>> _eventControllers =
       <String, StreamController<ServiceEvent>>{};
 
-  Set<String> _listeningFor = new Set<String>();
+  final Set<String> _listeningFor = new Set<String>();
 
   /// Whether our connection to the VM service has been closed;
   bool get isClosed => _peer.isClosed;