Stream based command used for location

RxDart added, Stream based Command used to fetch location.  UI was reworked for more symmetry and a better look.  lastKnownLocation method is not used to get location anymore because it is inconsistent.  CurrentLocation method is now used in its place.  

New Object made to combine the two boolean Obervables so that they can disable both the location and weather commands based on more complex logic.

Author: Tensor-Programming

lib/const.dart

@@ -1 +1 @@
-const API_KEY = '[OPEN WEATHER MAP API KEY HERE]';
+const API_KEY = '[API KEY HERE]';

lib/main.dart

@@ -5,6 +5,10 @@ import 'package:weather/model/model_command.dart';
 import 'package:weather/model/model.dart';
 import 'package:weather/model/model_provider.dart';
 
+//unimport if you need the initState function stuff.
+
+// import 'package:geolocation/geolocation.dart';
+
 import 'package:rx_widgets/rx_widgets.dart';
 
 import 'package:http/http.dart' as http;
@@ -37,8 +41,20 @@ class MyHomePage extends StatefulWidget {
 }
 
 class _MyHomePageState extends State<MyHomePage> {
+  @override
+  void initState() {
+    super.initState();
+    //If Geolocation is unable to get location in emulator, uncomment this and then restart the program.
+    //This tends to fix the error and you can see if the GPS is actually getting the location.
+    // var x = Geolocation.locationUpdates(
+    //     accuracy: LocationAccuracy.best, inBackground: false);
+    // x.listen((d) => print(d.isSuccessful));
+  }
+
   @override
   Widget build(BuildContext context) {
+    //call to getGpsCommand handler on build.  If GPS is active comes back with true, else false.
+    ModelProvider.of(context).getGpsCommand.call();
     return Scaffold(
       appBar: AppBar(
         title: Text('Weather App'),
@@ -48,20 +64,25 @@ class _MyHomePageState extends State<MyHomePage> {
               child: RxLoader<bool>(
                 radius: 20.0,
                 commandResults: ModelProvider.of(context).getGpsCommand,
-                dataBuilder: (context, data) =>
-                    Text(data ? "GPS Active" : "GPS Inactive"),
+                dataBuilder: (context, data) => Row(
+                      children: <Widget>[
+                        Text(data ? "GPS is Active" : "GPS is Inactive"),
+                        // Added logic to change the Icon when GPS is inactive.
+                        IconButton(
+                          icon: Icon(
+                              data ? Icons.gps_fixed : Icons.gps_not_fixed),
+                          onPressed: ModelProvider.of(context).getGpsCommand,
+                        ),
+                      ],
+                    ),
                 placeHolderBuilder: (context) => Text("Push the Button"),
                 errorBuilder: (context, exception) => Text("$exception"),
               ),
             ),
           ),
-          IconButton(
-            icon: Icon(Icons.gps_fixed),
-            onPressed: ModelProvider.of(context).getGpsCommand,
-          ),
           PopupMenuButton<int>(
             padding: EdgeInsets.all(1.0),
-            tooltip: "Select how much data you want",
+            tooltip: "Select how many cities you want",
             onSelected: (int item) {
               ModelProvider.of(context).addCitiesCommand(item);
             },
@@ -70,7 +91,7 @@ class _MyHomePageState extends State<MyHomePage> {
                   .map((number) => PopupMenuItem(
                         value: number,
                         child: Center(
-                          child: Text(number.toString()),
+                          child: Text("$number Cities"),
                         ),
                       ))
                   .toList();
@@ -95,32 +116,32 @@ class _MyHomePageState extends State<MyHomePage> {
             padding: EdgeInsets.all(10.0),
             child: Row(
               children: <Widget>[
-                Container(
-                  padding: EdgeInsets.all(5.0),
+                //changed to expanded for more consistency.
+                Expanded(
                   child: WidgetSelector(
                     buildEvents: ModelProvider
                         .of(context)
-                        .updateLocationCommand
+                        .updateWeatherCommand
                         .canExecute,
                     onTrue: MaterialButton(
                       elevation: 5.0,
                       color: Colors.blueGrey,
                       child: Text("Get the Weather"),
                       onPressed: ModelProvider
                           .of(context)
-                          .updateLocationCommand
-                          .execute,
+                          .updateLocationStreamCommand
+                          .call,
                     ),
                     onFalse: MaterialButton(
                       elevation: 0.0,
                       color: Colors.blueGrey,
                       onPressed: null,
-                      child: Text("Loading..."),
+                      child: Text("Loading Data....."),
                     ),
                   ),
                 ),
-                Container(
-                  padding: EdgeInsets.only(left: 90.0),
+                //changed to expanded for more consistency.
+                Expanded(
                   child: Column(
                     children: <Widget>[
                       SliderItem(

lib/model/model_command.dart

@@ -1,52 +1,90 @@
 import 'package:rx_command/rx_command.dart';
 import 'package:geolocation/geolocation.dart';
+import 'package:rxdart/rxdart.dart';
+import 'package:rxdart/streams.dart';
 
 import 'package:weather/model/model.dart';
 import 'package:weather/model/weather_repo.dart';
 
 class ModelCommand {
   final WeatherRepo weatherRepo;
 
-  final RxCommand<Null, LocationResult> updateLocationCommand;
+  // final RxCommand<Null, LocationResult> updateLocationCommand;
   final RxCommand<LocationResult, List<WeatherModel>> updateWeatherCommand;
   final RxCommand<Null, bool> getGpsCommand;
   final RxCommand<bool, bool> radioCheckedCommand;
   final RxCommand<int, Null> addCitiesCommand;
+  final RxCommand<dynamic, LocationResult> updateLocationStreamCommand;
 
   ModelCommand._(
     this.weatherRepo,
-    this.updateLocationCommand,
+    // this.updateLocationCommand,
     this.updateWeatherCommand,
     this.getGpsCommand,
     this.radioCheckedCommand,
     this.addCitiesCommand,
+    this.updateLocationStreamCommand,
   );
 
   factory ModelCommand(WeatherRepo repo) {
     final _getGpsCommand = RxCommand.createAsync2<bool>(repo.getGps);
 
     final _radioCheckedCommand = RxCommand.createSync3<bool, bool>((b) => b);
 
-    final _updateLocationCommand = RxCommand.createAsync2<LocationResult>(
-        repo.updateLocation, _getGpsCommand.results);
+    //A combined Observable of the GPS and Radio observables using And logic.  If one is false then false will be returned.
+    //This allows us to have a more dynamic set of circumstances for shutting down the buttons.
+    // final Observable<bool> _boolCombine = Observable
+    //     .combineLatest2(_getGpsCommand.results, _radioCheckedCommand.results,
+    //         (gps, radio) => gps && radio)
+    //     .distinctUnique();
+
+    //Two Observables needed because they are only cold observables (single subscription).
+    final _boolCombineA =
+        CombineObs(_getGpsCommand.results, _radioCheckedCommand.results)
+            .combinedObservable;
+    final _boolCombineB =
+        CombineObs(_getGpsCommand.results, _radioCheckedCommand.results)
+            .combinedObservable;
+
+    // final _updateLocationCommand =
+    //     RxCommand.createAsync2<LocationResult>(repo.updateLocation);
 
     final _updateWeatherCommand =
         RxCommand.createAsync3<LocationResult, List<WeatherModel>>(
-            repo.updateWeather, _radioCheckedCommand.results);
+            repo.updateWeather, _boolCombineA);
 
     final _addCitiesCommand = RxCommand.createSync1<int>(repo.addCities);
 
-    _updateLocationCommand.results.listen(_updateWeatherCommand);
+    final _updateLocationStreamCommand =
+        RxCommand.createFromStream<dynamic, LocationResult>(
+            repo.updateLocationStream, _boolCombineB);
+
+    // _updateLocationCommand.results.listen(_updateWeatherCommand);
+    //using a stream based command now because lastKnownLocation is not as consistent as [currentLocation]
+    _updateLocationStreamCommand.results
+        .listen((data) => _updateWeatherCommand(data));
 
     _updateWeatherCommand(null);
 
     return ModelCommand._(
       repo,
-      _updateLocationCommand,
+      // _updateLocationCommand,
       _updateWeatherCommand,
       _getGpsCommand,
       _radioCheckedCommand,
       _addCitiesCommand,
+      _updateLocationStreamCommand,
     );
   }
 }
+
+class CombineObs {
+  final Observable<bool> _combinedObservable;
+  Observable<bool> get combinedObservable => _combinedObservable;
+  CombineObs._(this._combinedObservable);
+
+  factory CombineObs(a, b) {
+    Observable<bool> c = Observable.combineLatest2(a, b, (x, y) => x && y);
+    return CombineObs._(c);
+  }
+}

lib/model/weather_repo.dart

@@ -41,9 +41,18 @@ class WeatherRepo {
     return req;
   }
 
-  Future<LocationResult> updateLocation() async {
-    Future<LocationResult> result = Geolocation.lastKnownLocation();
-    return result;
+  // Future<LocationResult> updateLocation() async {
+  //   Future<LocationResult> result = Geolocation.lastKnownLocation();
+  //   return result;
+  // }
+
+  //uses Stream instead of future.  Mainly done because lastKnownLocation isn't as reliable as locationUpdates.
+  //when geolocation plugin is fixed or better plugin is released, will update code.
+
+  Stream<LocationResult> updateLocationStream(dynamic item) {
+    Stream<LocationResult> stream = Geolocation.currentLocation(
+        accuracy: LocationAccuracy.best, inBackground: false);
+    return stream;
   }
 
   Future<bool> getGps() async {

pubspec.yaml

@@ -13,6 +13,7 @@ dependencies:
   rx_command: "^1.0.7"
   rx_widgets: "^1.0.2"
   geolocation: "^0.2.1"
+  rxdart: "^0.16.6"