feat: check specific host

README.md

@@ -31,6 +31,8 @@ class DemoPage extends StatelessWidget {
         title: new Text("Offline Demo"),
       ),
       body: OfflineBuilder(
+        checkHost : true, // check if internet is avaiable by a DNS request , the default value is false
+        // hostToCheck : "my.domaine.name", // the default value is google.com 
         connectivityBuilder: (
           BuildContext context,
           ConnectivityResult connectivity,

example/lib/demo_page.dart

@@ -1,19 +1,14 @@
 import 'package:flutter/material.dart';
 
 class DemoPage extends StatelessWidget {
-  const DemoPage({
-    Key key,
-    @required this.child,
-  }) : super(key: key);
+  const DemoPage({Key key, @required this.child}) : super(key: key);
 
   final Widget child;
 
   @override
   Widget build(BuildContext context) {
     return Scaffold(
-      appBar: AppBar(
-        title: Text("Offline Demo"),
-      ),
+      appBar: AppBar(title: Text("Offline Demo")),
       body: child,
     );
   }

example/lib/main.dart

@@ -13,41 +13,17 @@ class MyApp extends StatelessWidget {
     return MaterialApp(
       title: 'Offline Demo',
       theme: ThemeData.dark(),
-      home: Builder(
-        builder: (BuildContext context) {
-          return Column(
-            mainAxisAlignment: MainAxisAlignment.center,
-            children: <Widget>[
-              RaisedButton(
-                child: Text("Demo 1"),
-                onPressed: () {
-                  navigate(context, Demo1());
-                },
-              ),
-              RaisedButton(
-                child: Text("Demo 2"),
-                onPressed: () {
-                  navigate(context, Demo2());
-                },
-              ),
-              RaisedButton(
-                child: Text("Demo 3"),
-                onPressed: () {
-                  navigate(context, Demo3());
-                },
-              ),
-            ],
-          );
-        },
+      home: Column(
+        mainAxisAlignment: MainAxisAlignment.center,
+        children: <Widget>[
+          RaisedButton(child: Text("Demo 1"), onPressed: () => navigate(context, Demo1())),
+          RaisedButton(child: Text("Demo 2"), onPressed: () => navigate(context, Demo2())),
+          RaisedButton(child: Text("Demo 3"), onPressed: () => navigate(context, Demo3())),
+        ],
       ),
     );
   }
 
-  void navigate(BuildContext context, Widget widget) {
-    Navigator.of(context).push<void>(
-      MaterialPageRoute<void>(
-        builder: (BuildContext context) => DemoPage(child: widget),
-      ),
-    );
-  }
+  void navigate(BuildContext context, Widget widget) =>
+      Navigator.of(context).push<void>(MaterialPageRoute<void>(builder: (_) => DemoPage(child: widget)));
 }

example/lib/widgets/demo_1.dart

@@ -5,12 +5,8 @@ class Demo1 extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return OfflineBuilder(
-      connectivityBuilder: (
-        BuildContext context,
-        ConnectivityResult connectivity,
-        Widget child,
-      ) {
-        final bool connected = connectivity != ConnectivityResult.none;
+      connectivityBuilder: (BuildContext context, ConnectivityResult connectivity, Widget child) {
+        final bool isConnected = connectivity != ConnectivityResult.none;
         return Stack(
           fit: StackFit.expand,
           children: [
@@ -21,26 +17,10 @@ class Demo1 extends StatelessWidget {
               right: 0.0,
               child: AnimatedContainer(
                 duration: const Duration(milliseconds: 350),
-                color: connected ? Color(0xFF00EE44) : Color(0xFFEE4400),
+                color: isConnected ? Color(0xFF00EE44) : Color(0xFFEE4400),
                 child: AnimatedSwitcher(
                   duration: const Duration(milliseconds: 350),
-                  child: connected
-                      ? Text('ONLINE')
-                      : Row(
-                          mainAxisAlignment: MainAxisAlignment.center,
-                          children: <Widget>[
-                            Text('OFFLINE'),
-                            SizedBox(width: 8.0),
-                            SizedBox(
-                              width: 12.0,
-                              height: 12.0,
-                              child: CircularProgressIndicator(
-                                strokeWidth: 2.0,
-                                valueColor: AlwaysStoppedAnimation<Color>(Colors.white),
-                              ),
-                            ),
-                          ],
-                        ),
+                  child: isConnected ? Text('ONLINE') : _OfflineWidget(),
                 ),
               ),
             ),
@@ -50,14 +30,30 @@ class Demo1 extends StatelessWidget {
       child: Column(
         mainAxisAlignment: MainAxisAlignment.center,
         children: <Widget>[
-          Text(
-            'There are no bottons to push :)',
-          ),
-          Text(
-            'Just turn off your internet.',
-          ),
+          Text('There are no bottons to push :)'),
+          Text('Just turn off your internet.'),
         ],
       ),
     );
   }
 }
+
+class _OfflineWidget extends StatelessWidget {
+  const _OfflineWidget({Key key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Row(
+      mainAxisAlignment: MainAxisAlignment.center,
+      children: <Widget>[
+        Text('OFFLINE'),
+        SizedBox(width: 8.0),
+        SizedBox(
+          width: 12.0,
+          height: 12.0,
+          child: CircularProgressIndicator(strokeWidth: 2.0, valueColor: AlwaysStoppedAnimation<Color>(Colors.white)),
+        ),
+      ],
+    );
+  }
+}

example/lib/widgets/demo_2.dart

@@ -5,36 +5,25 @@ class Demo2 extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return OfflineBuilder(
-      connectivityBuilder: (
-        BuildContext context,
-        ConnectivityResult connectivity,
-        Widget child,
-      ) {
+      connectivityBuilder: (BuildContext context, ConnectivityResult connectivity, Widget child) {
         if (connectivity == ConnectivityResult.none) {
           return Container(
             color: Colors.white,
             child: Center(
-              child: Text(
-                "Oops, \n\nNow we are Offline!",
-                style: TextStyle(color: Colors.black),
-              ),
+              child: Text("Oops, \n\nNow we are Offline!", style: TextStyle(color: Colors.black)),
             ),
           );
-        } else {
-          return child;
         }
+
+        return child;
       },
       builder: (BuildContext context) {
         return Center(
           child: Column(
             mainAxisAlignment: MainAxisAlignment.center,
             children: <Widget>[
-              Text(
-                'There are no bottons to push :)',
-              ),
-              Text(
-                'Just turn off your internet.',
-              ),
+              Text('There are no bottons to push :)'),
+              Text('Just turn off your internet.'),
             ],
           ),
         );

example/lib/widgets/demo_3.dart

@@ -6,37 +6,25 @@ class Demo3 extends StatelessWidget {
   Widget build(BuildContext context) {
     return OfflineBuilder(
       debounceDuration: Duration.zero,
-      connectivityBuilder: (
-        BuildContext context,
-        ConnectivityResult connectivity,
-        Widget child,
-      ) {
+      connectivityBuilder: (BuildContext context, ConnectivityResult connectivity, Widget child) {
         if (connectivity == ConnectivityResult.none) {
           return Container(
             color: Colors.white70,
             child: Center(
-              child: Text(
-                "Oops, \n\nWe experienced a Delayed Offline!",
-                style: TextStyle(color: Colors.black),
-              ),
+              child: Text("Oops, \n\nWe experienced a Delayed Offline!", style: TextStyle(color: Colors.black)),
             ),
           );
         }
+
         return child;
       },
       child: Center(
         child: Column(
           mainAxisAlignment: MainAxisAlignment.center,
           children: <Widget>[
-            Text(
-              'There are no bottons to push :)',
-            ),
-            Text(
-              'Just turn off your internet.',
-            ),
-            Text(
-              'This one has a bit of a delay.',
-            ),
+            Text('There are no bottons to push :)'),
+            Text('Just turn off your internet.'),
+            Text('This one has a bit of a delay.'),
           ],
         ),
       ),

lib/src/main.dart

@@ -5,12 +5,15 @@ import 'package:flutter/widgets.dart';
 import 'package:flutter_offline/src/utils.dart';
 
 const kOfflineDebounceDuration = Duration(seconds: 3);
+const kHostToCheck = 'google.com';
 
 class OfflineBuilder extends StatefulWidget {
   factory OfflineBuilder({
     Key key,
     @required ValueWidgetBuilder<ConnectivityResult> connectivityBuilder,
     Duration debounceDuration = kOfflineDebounceDuration,
+    String hostToCheck = kHostToCheck,
+    bool checkHost = false,
     WidgetBuilder builder,
     Widget child,
     WidgetBuilder errorBuilder,
@@ -20,6 +23,8 @@ class OfflineBuilder extends StatefulWidget {
       connectivityBuilder: connectivityBuilder,
       connectivityService: Connectivity(),
       debounceDuration: debounceDuration,
+      hostToCheck: hostToCheck,
+      checkHost: checkHost,
       builder: builder,
       child: child,
       errorBuilder: errorBuilder,
@@ -32,6 +37,8 @@ class OfflineBuilder extends StatefulWidget {
     @required this.connectivityBuilder,
     @required this.connectivityService,
     this.debounceDuration = kOfflineDebounceDuration,
+    this.hostToCheck = kHostToCheck,
+    this.checkHost = false,
     this.builder,
     this.child,
     this.errorBuilder,
@@ -40,6 +47,8 @@ class OfflineBuilder extends StatefulWidget {
         assert(connectivityService != null, 'connectivityService cannot be null'),
         assert(!(builder is WidgetBuilder && child is Widget) && !(builder == null && child == null),
             'You should specify either a builder or a child'),
+        assert(hostToCheck != null, 'hostToCheck cannot be null'),
+        assert(checkHost != null, 'checkHost can only be true or false'),
         super(key: key);
 
   /// Override connectivity service used for testing
@@ -48,6 +57,12 @@ class OfflineBuilder extends StatefulWidget {
   /// Debounce duration from epileptic network situations
   final Duration debounceDuration;
 
+  /// Hostname to test internet connection
+  final String hostToCheck;
+
+  /// Decide if to use the hostname option
+  final bool checkHost;
+
   /// Used for building the Offline and/or Online UI
   final ValueWidgetBuilder<ConnectivityResult> connectivityBuilder;
 
@@ -72,8 +87,13 @@ class OfflineBuilderState extends State<OfflineBuilder> {
     super.initState();
 
     _connectivityStream = Stream.fromFuture(widget.connectivityService.checkConnectivity())
-        .asyncExpand((data) => widget.connectivityService.onConnectivityChanged.transform(startsWith(data)))
-        .transform(debounce(widget.debounceDuration));
+        .asyncExpand((data) => widget.connectivityService.onConnectivityChanged.transform(startsWith(data)));
+
+    if (widget.checkHost) {
+      _connectivityStream = _connectivityStream.transform(checkIfHostIsAvailble(widget.hostToCheck));
+    }
+
+    _connectivityStream = _connectivityStream.transform(debounce(widget.debounceDuration));
   }
 
   @override

lib/src/utils.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:io';
 
 import 'package:connectivity/connectivity.dart';
 
@@ -55,3 +56,22 @@ StreamTransformer<ConnectivityResult, ConnectivityResult> startsWith(
     },
   );
 }
+
+StreamTransformer<ConnectivityResult, ConnectivityResult> checkIfHostIsAvailble(String host) {
+  return StreamTransformer<ConnectivityResult, ConnectivityResult>.fromHandlers(
+    handleData: (ConnectivityResult data, EventSink<ConnectivityResult> sink) async {
+      try {
+        final result = await InternetAddress.lookup(host);
+        if (result.isNotEmpty && result[0].rawAddress.isNotEmpty) {
+          sink.add(data);
+          return;
+        }
+
+        throw SocketException("");
+      } on SocketException catch (_) {
+        sink.add(ConnectivityResult.none);
+      }
+    },
+    handleDone: (EventSink<ConnectivityResult> sink) => sink.close(),
+  );
+}