An example showing how to send messages between the host app and Flutter

examples/hello_android/app/src/flutter/lib/main.dart

@@ -2,6 +2,71 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+import 'dart:convert';
+import 'dart:math';
+
+import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
+import 'package:flutter/services.dart';
+
+final Random random = new Random();
+
+Future<String> handleGetRandom(String json) async {
+  Map message = JSON.decode(json);
+  double min = message['min'].toDouble();
+  double max = message['max'].toDouble();
+
+  double value = (random.nextDouble() * (max - min)) + min;
+
+  Map reply = {'value': value};
+  return JSON.encode(reply);
+}
+
+class HelloAndroid extends StatefulWidget {
+  @override
+  _HelloAndroidState createState() => new _HelloAndroidState();
+}
+
+class _HelloAndroidState extends State<HelloAndroid> {
+  double _latitude;
+  double _longitude;
+
+  @override
+  Widget build(BuildContext context) {
+    return new Material(
+      child: new Center(
+        child: new Column(
+          children: <Widget>[
+            new Text('Hello from Flutter!'),
+            new RaisedButton(
+              child: new Text('Get Location'),
+              onPressed: _getLocation
+            ),
+            new Text('Latitude: ${_latitude}, Longitude: ${_longitude}'),
+          ]
+        )
+      )
+    );
+  }
+
+  void _getLocation() {
+    Map message = {'provider': 'network'};
+    HostMessages.sendToHost('getLocation', JSON.encode(message))
+        .then(_onReceivedLocation);
+  }
+
+  void _onReceivedLocation(String json) {
+    Map reply = JSON.decode(json);
+    setState(() {
+      _latitude = reply['latitude'];
+      _longitude = reply['longitude'];
+    });
+  }
+}
+
+void main() {
+  runApp(new HelloAndroid());
 
-void main() => runApp(new Center(child: new Text('Hello from Flutter!')));
+  HostMessages.addMessageHandler('getRandom', handleGetRandom);
+}

examples/hello_android/app/src/main/AndroidManifest.xml

@@ -6,14 +6,15 @@
 
     <uses-sdk android:minSdkVersion="16" android:targetSdkVersion="21" />
     <uses-permission android:name="android.permission.INTERNET"/>
+    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
 
     <application android:name="org.domokit.sky.shell.SkyApplication" android:label="@string/app_name" >
         <activity
-            android:name=".FlutterActivity"
-            android:label="@string/app_name"
-            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection"
+            android:name=".ExampleActivity"
             android:launchMode="singleTask"
             android:theme="@android:style/Theme.Black.NoTitleBar"
+            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection"
+            android:hardwareAccelerated="true"
             android:windowSoftInputMode="adjustResize">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />

examples/hello_android/app/src/main/java/com/example/flutter/ExampleActivity.java

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package com.example.flutter;
+
+import android.app.Activity;
+import android.content.Context;
+import android.location.Location;
+import android.location.LocationManager;
+import android.os.Bundle;
+import android.util.Log;
+import android.view.View;
+import android.widget.Button;
+import android.widget.TextView;
+
+import org.chromium.base.PathUtils;
+import org.domokit.activity.ActivityImpl;
+import org.domokit.sky.shell.SkyMain;
+import org.domokit.sky.shell.PlatformViewAndroid;
+
+import java.io.File;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+public class ExampleActivity extends Activity {
+    private static final String TAG = "ExampleActivity";
+
+    private PlatformViewAndroid flutterView;
+
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        SkyMain.ensureInitialized(getApplicationContext(), null);
+        setContentView(R.layout.flutter_layout);
+
+        flutterView = (PlatformViewAndroid) findViewById(R.id.flutter_view);
+        File appBundle = new File(PathUtils.getDataDirectory(this), SkyMain.APP_BUNDLE);
+        flutterView.runFromBundle(appBundle.getPath(), null);
+
+        flutterView.addOnMessageListener("getLocation",
+            new PlatformViewAndroid.OnMessageListener() {
+                @Override
+                public String onMessage(String message) {
+                    return onGetLocation(message);
+                }
+            });
+
+        Button getRandom = (Button) findViewById(R.id.get_random);
+        getRandom.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                sendGetRandom();
+            }
+        });
+    }
+
+    @Override
+    protected void onDestroy() {
+        if (flutterView != null) {
+            flutterView.destroy();
+        }
+        super.onDestroy();
+    }
+
+    @Override
+    protected void onPause() {
+        super.onPause();
+        flutterView.onPause();
+    }
+
+    @Override
+    protected void onResume() {
+        super.onResume();
+        flutterView.onResume();
+    }
+
+    private void sendGetRandom() {
+        JSONObject message = new JSONObject();
+        try {
+            message.put("min", 1);
+            message.put("max", 1000);
+        } catch (JSONException e) {
+            Log.e(TAG, "JSON exception", e);
+            return;
+        }
+
+        flutterView.sendToFlutter("getRandom", message.toString(),
+            new PlatformViewAndroid.MessageReplyCallback() {
+                @Override
+                public void onReply(String json) {
+                    onRandomReply(json);
+                }
+            });
+    }
+
+    private void onRandomReply(String json) {
+        double value;
+        try {
+            JSONObject reply = new JSONObject(json);
+            value = reply.getDouble("value");
+        } catch (JSONException e) {
+            Log.e(TAG, "JSON exception", e);
+            return;
+        }
+
+        TextView randomValue = (TextView) findViewById(R.id.random_value);
+        randomValue.setText(Double.toString(value));
+    }
+
+    private String onGetLocation(String json) {
+        String provider;
+        try {
+            JSONObject message = new JSONObject(json);
+            provider = message.getString("provider");
+        } catch (JSONException e) {
+            Log.e(TAG, "JSON exception", e);
+            return null;
+        }
+
+        String locationProvider;
+        if (provider.equals("network")) {
+            locationProvider = LocationManager.NETWORK_PROVIDER;
+        } else if (provider.equals("gps")) {
+            locationProvider = LocationManager.GPS_PROVIDER;
+        } else {
+            return null;
+        }
+
+        LocationManager locationManager =
+            (LocationManager) getSystemService(Context.LOCATION_SERVICE);
+        Location location = locationManager.getLastKnownLocation(locationProvider);
+
+        JSONObject reply = new JSONObject();
+        try {
+            reply.put("latitude", location.getLatitude());
+            reply.put("longitude", location.getLongitude());
+        } catch (JSONException e) {
+            Log.e(TAG, "JSON exception", e);
+            return null;
+        }
+
+        return reply.toString();
+    }
+}

examples/hello_android/app/src/main/java/com/example/flutter/FlutterActivity.java

-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package com.example.flutter;
-
-import android.app.Activity;
-import android.os.Bundle;
-
-import org.chromium.base.PathUtils;
-import org.domokit.sky.shell.SkyMain;
-import org.domokit.sky.shell.PlatformViewAndroid;
-
-import java.io.File;
-
-public class FlutterActivity extends Activity {
-    private PlatformViewAndroid flutterView;
-
-    @Override
-    public void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-
-        SkyMain.ensureInitialized(getApplicationContext(), null);
-        setContentView(R.layout.flutter_layout);
-
-        flutterView = (PlatformViewAndroid) findViewById(R.id.flutter_view);
-        File appBundle = new File(PathUtils.getDataDirectory(this), SkyMain.APP_BUNDLE);
-        flutterView.runFromBundle(appBundle.getPath(), null);
-    }
-
-    @Override
-    protected void onDestroy() {
-        if (flutterView != null) {
-            flutterView.destroy();
-        }
-        super.onDestroy();
-    }
-}

examples/hello_android/app/src/main/res/layout/flutter_layout.xml

@@ -4,15 +4,36 @@
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"
     >
+
   <TextView
       android:id="@+id/text_view"
       android:layout_width="fill_parent"
       android:layout_height="wrap_content"
       android:text="@string/title"
       />
+
+  <LinearLayout
+      android:orientation="horizontal"
+      android:layout_width="fill_parent"
+      android:layout_height="wrap_content"
+      >
+      <Button
+          android:id="@+id/get_random"
+          android:layout_width="wrap_content"
+          android:layout_height="wrap_content"
+          android:text="@string/get_random"
+          />
+      <TextView
+          android:id="@+id/random_value"
+          android:layout_width="wrap_content"
+          android:layout_height="wrap_content"
+          />
+  </LinearLayout>
+
   <org.domokit.sky.shell.PlatformViewAndroid
       android:id="@+id/flutter_view"
       android:layout_width="fill_parent"
       android:layout_height="fill_parent"
       />
+
 </LinearLayout>

examples/hello_android/app/src/main/res/values/strings.xml

@@ -2,4 +2,5 @@
 <resources>
     <string name="app_name">Flutter App</string>
     <string name="title">Flutter Application</string>
+    <string name="get_random">Get Random Number</string>
 </resources>