PacktPublishing · bissenbay · Oct 16, 2021
diff --git a/chapter_07/lib/generated_plugin_registrant.dart b/chapter_07/lib/generated_plugin_registrant.dart
diff --git a/chapter_07/lib/geolocation.dart b/chapter_07/lib/geolocation.dart
@@ -0,0 +1,44 @@
+import 'package:flutter/material.dart';
+import 'package:geolocator/geolocator.dart';
+
+class LocationScreen extends StatefulWidget {
+  const LocationScreen({Key? key}) : super(key: key);
+
+  @override
+  _LocationScreenState createState() => _LocationScreenState();
+}
+
+class _LocationScreenState extends State<LocationScreen> {
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text('Current Location'),
+      ),
+      body: Center(
+        child: FutureBuilder(
+          future: getPosition(),
+          builder: (BuildContext context, AsyncSnapshot<dynamic> snapshot) {
+            if (snapshot.connectionState == ConnectionState.waiting) {
+              return const CircularProgressIndicator();
+            } else if (snapshot.connectionState == ConnectionState.done) {
+              if (snapshot.hasError) {
+                return const Text('Something terrible happened!');
+              }
+              return Text(snapshot.data);
+            } else {
+              return const Text('');
+            }
+          },
+        ),
+      ),
+    );
+  }
+
+  Future<Position> getPosition() async {
+    await Future<int>.delayed(const Duration(seconds: 3));
+    Position? position = await Geolocator.getCurrentPosition(
+        desiredAccuracy: LocationAccuracy.high);
+    return position;
+  }
+}
diff --git a/chapter_07/lib/location_screen.dart b/chapter_07/lib/location_screen.dart
diff --git a/chapter_07/lib/main.dart b/chapter_07/lib/main.dart
@@ -3,17 +3,16 @@ import 'package:cookbook_ch_07/navigation_first.dart';
 import 'package:flutter/material.dart';
 import 'package:async/async.dart';
 import 'package:geolocator/geolocator.dart';
-import 'package:http/http.dart';
 import 'package:http/http.dart' as http;
 
-import 'location_screen.dart';
+import 'geolocation.dart';
 import 'navigation_dialog.dart';
 
-void main() {
-  runApp(MyApp());
-}
+void main() => runApp(const MyApp());
 
 class MyApp extends StatelessWidget {
+  const MyApp({Key? key}) : super(key: key);
+
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
@@ -22,20 +21,22 @@ class MyApp extends StatelessWidget {
         primarySwatch: Colors.blue,
         visualDensity: VisualDensity.adaptivePlatformDensity,
       ),
-      home: NavigationDialog(),
+      home: const NavigationDialog(),
     );
   }
 }
 
 class FuturePage extends StatefulWidget {
+  const FuturePage({Key? key}) : super(key: key);
+
   @override
   _FuturePageState createState() => _FuturePageState();
 }
 
 class _FuturePageState extends State<FuturePage> {
-  String result;
-  Completer completer;
-  Future<int> getNumber() {
+  String result = "";
+  late Completer completer;
+  Future getNumber() {
     completer = Completer<int>();
     calculate();
     return completer.future;
@@ -50,31 +51,22 @@ class _FuturePageState extends State<FuturePage> {
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(
-        title: Text('Back from the Future'),
+        title: const Text('Back from the Future'),
       ),
       body: Center(
         child: Column(children: [
-          Spacer(),
+          const Spacer(),
           ElevatedButton(
-            child: Text('GO!'),
+            child: const Text('GO!'),
             onPressed: () {
-              returnError()
-              .then((value){
-                setState(() {
-                  result = 'Success';
-                });
-              }).catchError((onError){
-                setState(() {
-                  result = onError;
-                });
-              }).whenComplete(() => print('Complete'));
+              handleError();
             },
           ),
-          Spacer(),
+          constSpacer(),
           Text(result.toString()),
-          Spacer(),
-          CircularProgressIndicator(),
-          Spacer(),
+          const Spacer(),
+          const CircularProgressIndicator(),
+          const Spacer(),
         ]),
       ),
     );
@@ -111,11 +103,11 @@ class _FuturePageState extends State<FuturePage> {
     futureGroup.add(returnTwoAsync());
     futureGroup.add(returnThreeAsync());
     futureGroup.close();
-    futureGroup.future.then((List <int> value) {
+    futureGroup.future.then((List<int> value) {
       int total = 0;
-      value.forEach((element) { 
+      for (var element in value) {
         total += element;
-      });
+      }
       setState(() {
         result = total.toString();
       });
@@ -126,9 +118,15 @@ class _FuturePageState extends State<FuturePage> {
     throw ('Something terrible happened!');
   }
 
-  Future<Position> getPosition() async {
-    Position position = await Geolocator.getCurrentPosition(desiredAccuracy: LocationAccuracy.high);
-    return position;
+  Future handleError() async {
+    try {
+      await returnError();
+    } catch (error) {
+      setState(() {
+        result = error.toString();
+      });
+    } finally {
+      print('Complete');
+    }
   }
-
 }
diff --git a/chapter_07/lib/navigation_dialog.dart b/chapter_07/lib/navigation_dialog.dart
@@ -1,25 +1,28 @@
 import 'package:flutter/material.dart';
 
 class NavigationDialog extends StatefulWidget {
+  const NavigationDialog({Key? key}) : super(key: key);
+
   @override
   _NavigationDialogState createState() => _NavigationDialogState();
 }
 
 class _NavigationDialogState extends State<NavigationDialog> {
-  Color color = Colors.blue[700];
+  Color? color = Colors.blue[700];
   @override
   Widget build(BuildContext context) {
     return Scaffold(
       backgroundColor: color,
       appBar: AppBar(
-        title: Text('Navigation Dialog Screen'),
+        title: const Text('Navigation Dialog Screen'),
       ),
       body: Center(
         child: ElevatedButton(
-            child: Text('Change Color'),
-            onPressed: () {
-              _showColorDialog(context);
-            }),
+          child: const Text('Change Color'),
+          onPressed: () {
+            _showColorDialog(context);
+          },
+        ),
       ),
     );
   }
@@ -31,25 +34,25 @@ class _NavigationDialogState extends State<NavigationDialog> {
       context: context,
       builder: (_) {
         return AlertDialog(
-          title: Text('Very important question'),
-          content: Text('Please choose a color'),
+          title: const Text('Very important question'),
+          content: const Text('Please choose a color'),
           actions: <Widget>[
             TextButton(
-                child: Text('Red'),
+                child: const Text('Red'),
                 onPressed: () {
-                  color = Colors.red[700];
+                  color = Colors.red;
                   Navigator.pop(context, color);
                 }),
             TextButton(
-                child: Text('Green'),
+                child: const Text('Green'),
                 onPressed: () {
-                  color = Colors.green[700];
+                  color = Colors.green;
                   Navigator.pop(context, color);
                 }),
             TextButton(
-                child: Text('Blue'),
+                child: const Text('Blue'),
                 onPressed: () {
-                  color = Colors.blue[700];
+                  color = Colors.blue;
                   Navigator.pop(context, color);
                 }),
           ],

diff --git a/chapter_07/lib/navigation_first.dart b/chapter_07/lib/navigation_first.dart
@@ -1,24 +1,25 @@
 import 'package:flutter/material.dart';
-
 import 'navigation_second.dart';
 
 class NavigationFirst extends StatefulWidget {
+  const NavigationFirst({Key? key}) : super(key: key);
+
   @override
   _NavigationFirstState createState() => _NavigationFirstState();
 }
 
 class _NavigationFirstState extends State<NavigationFirst> {
-  Color color = Colors.blue[700];
+  Color color = Colors.blue;
   @override
   Widget build(BuildContext context) {
     return Scaffold(
       backgroundColor: color,
       appBar: AppBar(
-        title: Text('Navigation First Screen'),
+        title: const Text('Navigation First Screen'),
       ),
       body: Center(
         child: ElevatedButton(
-            child: Text('Change Color'),
+            child: const Text('Change Color'),
             onPressed: () {
               _navigateAndGetColor(context);
             }),

diff --git a/chapter_07/lib/navigation_second.dart b/chapter_07/lib/navigation_second.dart
@@ -1,6 +1,8 @@
 import 'package:flutter/material.dart';
 
 class NavigationSecond extends StatefulWidget {
+  const NavigationSecond({Key? key}) : super(key: key);
+
   @override
   _NavigationSecondState createState() => _NavigationSecondState();
 }
@@ -11,28 +13,28 @@ class _NavigationSecondState extends State<NavigationSecond> {
     Color color;
     return Scaffold(
         appBar: AppBar(
-          title: Text('Navigation Second Screen'),
+          title: const Text('Navigation Second Screen'),
         ),
         body: Center(
           child: Column(
             mainAxisAlignment: MainAxisAlignment.spaceEvenly,
             children: <Widget>[
               ElevatedButton(
-                  child: Text('Red'),
+                  child: const Text('Red'),
                   onPressed: () {
-                    color = Colors.red[700];
+                    color = Colors.red;
                     Navigator.pop(context, color);
                   }),
               ElevatedButton(
-                  child: Text('Green'),
+                  child: const Text('Green'),
                   onPressed: () {
-                    color = Colors.green[700];
+                    color = Colors.green;
                     Navigator.pop(context, color);
                   }),
               ElevatedButton(
-                  child: Text('Blue'),
+                  child: const Text('Blue'),
                   onPressed: () {
-                    color = Colors.blue[700];
+                    color = Colors.blue;
                     Navigator.pop(context, color);
                   }),
             ],

diff --git a/chapter_07/pubspec.yaml b/chapter_07/pubspec.yaml
@@ -23,9 +23,9 @@ environment:
 dependencies:
   flutter:
     sdk: flutter
-  http: ^0.13.1
-  async: ^2.5.0
-  geolocator: ^7.0.3
+  http: ^0.13.4
+  async: 2.8.1
+  geolocator: ^7.7.0
 
   # The following adds the Cupertino Icons font to your application.
   # Use with the CupertinoIcons class for iOS style icons.