Develop Reference

how can I remove header and footer in Flutter WebView?

This is what I used
There's this video by Joannes Mike on YouTube I followed on how to remove header and footer in Flutter WebView but it seems flutter had upgraded her library and this functions don't work anymore.
Been at this for days and it seems no recent info is available.
Heres my code
import 'package:sportybet_betting_tips/main.dart';
import 'package:webview_flutter/webview_flutter.dart';
class sportybet_tips extends StatefulWidget {
const sportybet_tips({super.key});
#override
State<sportybet_tips> createState() => _sportybet_tipsState();
}
class _sportybet_tipsState extends State<sportybet_tips>
{
late final WebViewController controller;
#override
void initState(){
super.initState();
controller = WebViewController()
..loadRequest(Uri.parse('https://accessbettingtips.com/sportybet/'),);
// controller.addJavaScriptChannel(
// "document.getElementsByTagName('header')[0].style.display='none'", onMessageReceived: (JavaScriptMessage ) { });
// controller.loadRequest(Uri.parse('http://accessbettingtips.com'),);
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Sportybet Betting Tips'),
),
body: WebViewWidget(controller: controller),
// controller.evaluateJavascript(
// "document.getElementsByTagName('header')[0].style.display='none'");
// controller.loadRequest(Uri.parse('http://accessbettingtips.com'),);
);
}
// webview_flutter({required JavaScriptMode JavaScriptMode, required String initialUrl}) {}
}

in your onPageFinished method write like that :
onPageFinished: (url) async {
controller.runJavascript("document.getElementsByTagName('header')[0].style.display='none'");
},

Flutter webview with custom javascriptInterfaceAdapter or invoke JS using webview controller

I have an old java project that performs in andorid webview with addJavascriptInterface
mWebView.addJavascriptInterface(new JavascriptAdapter(), "AndroidFunctions");
Within JavascriptAdapter class there is several #JavascriptInterface functions. as example
class JavascriptAdapter {
#JavascriptInterface
getMacAddress(){
DeviceInfo deviceInfo = new DeviceInfo(activity);
return deviceInfo.getMacAddress();
}
}
now after opening the webview within android applications, using JS we can access that function like this way -
var strMacAddress = AndroidFunctions.getMACAddress();
Now I would like to achieve this thing on flutter. for that, I am using the flutter inAppWebview plugin.
also, I have tried flutter_webview, WKWebview.

Please take a look in this documentation for InAppWebView.
JavScriptInterface are normally used to call native methods from webview. I am assuming that the webpage calls the method, so, you have to return the Mac Address as it is presented in the documentation. But you need to change the way for calling the method for flutter by adding this sample(provided in documentation) to you webpage source.
<script>
window.addEventListener("flutterInAppWebViewPlatformReady", function(event) {
window.flutter_inappwebview.callHandler('handlerFoo')
.then(function(result) {
// print to the console the data coming
// from the Flutter side.
console.log(JSON.stringify(result));
window.flutter_inappwebview
.callHandler('handlerFooWithArgs', 1, true, ['bar', 5], {foo: 'baz'}, result);
});
});
</script>

You can inspect this Webview from google chrome.
chrome://inspect/#devices
and don't forget to add flutter_inappwebview: ^5.3.2 in your pubspec.yaml
the answer is already given in this link
I have just added for a quick look on SO.
import 'dart:async';
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:flutter_inappwebview/flutter_inappwebview.dart';
Future main() async {
WidgetsFlutterBinding.ensureInitialized();
if (Platform.isAndroid) {
await AndroidInAppWebViewController.setWebContentsDebuggingEnabled(true);
}
runApp(new MyApp());
}
class MyApp extends StatefulWidget {
#override
_MyAppState createState() => new _MyAppState();
}
class _MyAppState extends State<MyApp> {
InAppWebViewGroupOptions options = InAppWebViewGroupOptions(
android: AndroidInAppWebViewOptions(
useHybridComposition: true,
),);
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: Text("JavaScript Handlers")),
body: SafeArea(
child: Column(children: <Widget>[
Expanded(
child: InAppWebView(
initialData: InAppWebViewInitialData(
data: """
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
</head>
<body>
<h1>JavaScript Handlers</h1>
<script>
window.addEventListener("flutterInAppWebViewPlatformReady", function(event) {
window.flutter_inappwebview.callHandler('handlerFoo')
.then(function(result) {
// print to the console the data coming
// from the Flutter side.
console.log(JSON.stringify(result));
window.flutter_inappwebview
.callHandler('handlerFooWithArgs', 1, true, ['bar', 5], {foo: 'baz'}, result);
});
});
</script>
</body>
</html>
"""
),
initialOptions: options,
onWebViewCreated: (controller) {
controller.addJavaScriptHandler(handlerName: 'handlerFoo', callback: (args) {
// return data to the JavaScript side!
return {
'bar': 'bar_value', 'baz': 'baz_value'
};
});
controller.addJavaScriptHandler(handlerName: 'handlerFooWithArgs', callback: (args) {
print(args);
// it will print: [1, true, [bar, 5], {foo: baz}, {bar: bar_value, baz: baz_value}]
});
},
onConsoleMessage: (controller, consoleMessage) {
print(consoleMessage);
// it will print: {message: {"bar":"bar_value","baz":"baz_value"}, messageLevel: 1}
},
),
),
]))),
);
}
}

NanoHTTPD Android Library for Serving webpage for youtube playback

i am trying to play a youtube video in android through NanoHTTPD android web server library using a html form by providing the youtube id of some video in the served html file into the html form. So far i got the youtube video player working. And i also get the form post parameter from the html. But i having trouble combining the two.
AndroidWebServer.class
package com.martin.androidwebplayer;
import android.app.Activity;
import android.content.Context;
import fi.iki.elonen.NanoHTTPD;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.youtube.player.YouTubeInitializationResult;
import com.google.android.youtube.player.YouTubePlayer;
import com.google.android.youtube.player.YouTubePlayerView;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;
public class AndroidWebServer extends NanoHTTPD {
private static final String TAG = "HTTPServer";
private Context ctx;
public AndroidWebServer(int port, Context ctx) {
super(port);
this.ctx = ctx;
try {
Log.d("TAG", "Starting web server..");
start();
}
catch(IOException ioe) {
Log.e(TAG, "Unable to start the server");
ioe.printStackTrace();
}
}
#Override
public Response serve(IHTTPSession session) {
Map<String, String> parms = session.getParms();
String content = null;
content = readFile().toString();
if (session.getMethod() == Method.POST) {
Map<String, String> files = new HashMap<String, String>();
try {
session.parseBody(files);
} catch (IOException e) {
e.printStackTrace();
} catch (ResponseException e) {
e.printStackTrace();
}
**youtube(String.valueOf(session.getParms().get("fname")));**
return newFixedLengthResponse(String.valueOf(session.getParms().get("fname")));
}
return newFixedLengthResponse(content );
}
private StringBuffer readFile() {
BufferedReader reader = null;
StringBuffer buffer = new StringBuffer();
try {
reader = new BufferedReader(
new InputStreamReader
(ctx.getAssets().open("index.html"), "UTF-8"));
String mLine;
while ((mLine = reader.readLine()) != null) {
buffer.append(mLine);
buffer.append("\n");
}
}
catch(IOException ioe) {
ioe.printStackTrace();
}
finally {
if (reader != null)
try {
reader.close();
}
catch (IOException ioe) {}
}
return buffer;
}
public void stopServer() {
this.stop();
}
public void youtube(String link) {
// Get reference to the view of Video player
YouTubePlayerView ytPlayer = (YouTubePlayerView) ((Activity)ctx).findViewById(R.id.ytPlayer);
String api_key = "apikey";
ytPlayer.initialize(
api_key,
new YouTubePlayer.OnInitializedListener() {
// Implement two methods by clicking on red
// error bulb inside onInitializationSuccess
// method add the video link or the playlist
// link that you want to play In here we
// also handle the play and pause
// functionality
#Override
public void onInitializationSuccess(
YouTubePlayer.Provider provider,
YouTubePlayer youTubePlayer, boolean b) {
youTubePlayer.loadVideo(link);
youTubePlayer.play();
}
// Inside onInitializationFailure
// implement the failure functionality
// Here we will show toast
#Override
public void onInitializationFailure(YouTubePlayer.Provider provider,
YouTubeInitializationResult
youTubeInitializationResult) {
}
});
}
}
MainActivity.class
package com.martin.androidwebplayer;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.youtube.player.YouTubeBaseActivity;
import com.google.android.youtube.player.YouTubePlayerView;
import java.io.IOException;
public class MainActivity extends YouTubeBaseActivity {
private AndroidWebServer aws;
private YouTubePlayerView ytPlayer;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
YouTubePlayerView ytPlayer = (YouTubePlayerView) findViewById(R.id.ytPlayer);
aws = new AndroidWebServer(8180, MainActivity.this);
}
}
assets/index.html
<html>
<head>
<title>CSS Contact Form</title>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.3/css/bootstrap.min.css"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script>
function formSubmit(){
var fname = document.getElementById("fname").value;
var dataString = 'fname='+ fname;
jQuery.ajax({
url: "http://192.168.100.42:8180",
data: dataString,
type: "POST",
success:function(data){
$("#myForm").html(data);
},
error:function (){}
});
return true;
}
</script>
</head>
<body>
<h2>Contact Form</h2>
<form class="form" action="" method="post">
<p class="name">
<div id="myForm">
<input type="text" name="fname" id="fname"/>
<label for="fname">Name</label>
</p>
</div>
<p class="submit" >
<input type="button" onclick="formSubmit();" value="Send"/>
</p>
</form>
</body>
</html>

Dart: Load an html file into a Flutter Webview

Sthg makes me crazy, I try to write an html file on the disk using the path_provider plugin with the dart:io library.
Here is what I tried (OKAY):
Future<File> writeFile() async {
final file = await _localFile;
return file.writeAsString('<!DOCTYPE html><html lang="fr"> <head> <meta charset="UTF-8"> <title>test_design</title> ...');
}
then the file is loaded in a webview: OKAY
But if I try with a longer html file, it doesn't work anymore, eg :
return file.writeAsString(' html file containing js ');
Any idea?
or how to load an html file (the file is not static) in a Flutter webview ?
I use flutter_webview_plugin.dart
(https://pub.dartlang.org/packages/flutter_webview_plugin)
webview code :
writeFile().then((file){
readFile().then((r){
_localPath.then((path){
var uri='file:///'+path+'/index.html';
flutterWebViewPlugin.launch(uri,
rect: new Rect.fromLTWH(
0.0,
400.0,
MediaQuery.of(context).size.width,
200.0,
),
);

IMO, this is the approach for this:
This is an example approach, I will be building a Flutter app that can read file and write data to file for later use.
It is an app that could write the String to text.txt file. Everytime the app is launched it will display the contents of text.txt.
I need a place to write data on disk and read it again when the app loads. So I used path_provider plugin to access Documents directory (on iOS, this corresponds to NSDocumentDirectory, on Android, this is the AppData directory).
Future<String> get _localPath async {
final directory = await getApplicationDocumentsDirectory();
return directory.path;
}
Create a reference to the File full location (in our case, the text.txt file), we use File class from the dart:io library.
Future<File> get _localFile async {
final path = await _localPath;
return File('$path/text.txt');
}
Need to write a string to a file using File writeAsString() method. It returns a Future<File> that completes with this File object once the entire operation has completed.
By default, writeAsString() creates the file and truncates the file if it already exists.
To append data to existing file, pass FileMode.append mode as second parameter.
Future<File> writeFile(String text) async {
final file = await _localFile;
return file.writeAsString('$text\r\n', mode: FileMode.append);
}
Use File readAsString() method to read the entire contents as a string. It returns a Future<String> that completes with the string once contents has been read.
Future<String> readFile() async {
try {
final file = await _localFile;
String content = await file.readAsString();
return content;
} catch (e) {
return '';
}
}
Here is the complete sample code:
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'dart:async';
import 'dart:io';
void main() {
runApp(
MaterialApp(
title: 'Read/Write Files',
home: MyApp(storage: TextStorage()),
),
);
}
class TextStorage {
Future<String> get _localPath async {
final directory = await getApplicationDocumentsDirectory();
return directory.path;
}
Future<File> get _localFile async {
final path = await _localPath;
return File('$path/text.txt');
}
Future<String> readFile() async {
try {
final file = await _localFile;
String content = await file.readAsString();
return content;
} catch (e) {
return '';
}
}
Future<File> writeFile(String text) async {
final file = await _localFile;
return file.writeAsString('$text\r\n', mode: FileMode.append);
}
Future<File> cleanFile() async {
final file = await _localFile;
return file.writeAsString('');
}
}
class MyApp extends StatefulWidget {
final TextStorage storage;
MyApp({Key key, #required this.storage}) : super(key: key);
#override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
TextEditingController _textField = new TextEditingController();
String _content = '';
#override
void initState() {
super.initState();
widget.storage.readFile().then((String text) {
setState(() {
_content = text;
});
});
}
Future<File> _writeStringToTextFile(String text) async {
setState(() {
_content += text + '\r\n';
});
return widget.storage.writeFile(text);
}
Future<File> _clearContentsInTextFile() async {
setState(() {
_content = '';
});
return widget.storage.cleanFile();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Read/Write File Example'),
backgroundColor: Colors.blue,
),
body: Container(
padding: EdgeInsets.all(20.0),
child: Column(
children: <Widget>[
TextField(
controller: _textField,
),
Padding(
padding: EdgeInsets.all(20.0),
child: RaisedButton(
child: Text('Write to File'),
color: Colors.lightBlueAccent,
onPressed: () {
if (_textField.text.isNotEmpty) {
_writeStringToTextFile(_textField.text);
_textField.clear();
}
},
),
),
Padding(
padding: EdgeInsets.only(bottom: 20.0),
child: RaisedButton(
child: Text(
'Clear Contents',
style: TextStyle(color: Colors.white),
),
color: Colors.grey,
onPressed: () {
_clearContentsInTextFile();
},
),
),
Expanded(
flex: 1,
child: new SingleChildScrollView(
child: Text(
'$_content',
style: TextStyle(
color: Colors.blue,
fontSize: 22.0,
),
),
),
),
],
),
),
);
}
}
Here's how it looks when run:
You can play around depending on your requirement.
Also for your other question on how to load an html file in Flutter webview, here is my approach:
You can actually make it work using the webview_flutter plugin.
Create an assets folder in the root directory of your Flutter application, then put your .html file in the assets folder.
You should add your .html file to under assets in your pubspec.yaml file.
pubspec.yaml
assets:
- assets/SampleHtml.html
Here is a sample implementation to load an html from a local file:
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:webview_flutter/webview_flutter.dart';
import 'dart:async';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
Future<String> localLoader() async {
return await rootBundle.loadString('assets/SampleHtml.html');
}
#override
Widget build(BuildContext context) {
return FutureBuilder<String>(
future: localLoader(),
builder: (context, snapshot) {
if (snapshot.hasData) {
return WebView(
initialUrl:
new Uri.dataFromString(snapshot.data, mimeType: 'text/html')
.toString(),
javascriptMode: JavascriptMode.unrestricted,
);
} else if (snapshot.hasError) {
return Text("${snapshot.error}");
}
return CircularProgressIndicator();
});
}
}
SampleHtml.html
<!DOCTYPE html>
<meta charset="utf-8">
<title>Sample HTML</title>
<html>
<head>
<link rel="stylesheet">
</head>
<body>
<h1>Flutter Webview</h1>
<p>A Flutter plugin that provides a WebView widget.</p>
<ul>
<li>List 1</li>
<li>List 2</li>
<li>List 3</li>
</ul>
</body>
</html>
This is how it looks like:

Flutter Webview two way communication with Javascript

I have an html file that I am loading in Flutter webview using flutter_webview_plugin. I am using evalJavascript to call function in my javascript code, meaning flutter(dart)->js. However, I also need some way to communicate back something to flutter(dart) layer, meaning js->flutter(dart).
I have tried using
- webkit.messageHandlers.native
- window.native
to support both platforms(Android,iOS) checking if those are available in JS. But, those comes as undefined. Using following code to get instance of native handler in JS.
typeof webkit !== 'undefined' ? webkit.messageHandlers.native :
window.native;
And even if I get that instance and post message using it, not sure how to handle it in flutter(dart) layer. I may need to use platform channels. Not sure, if I am in the right direction.
Is there any way through which I can do that? I have evaluated interactive_webview plugin. It works fine on Android. But, it has swift versioning issue and don't want to proceed further with that.
Any help would be appreciated.

Here is an example of communication from Javascript code to flutter.
In Flutter build your WebView like :
WebView(
initialUrl: url,
javascriptMode: JavascriptMode.unrestricted,
javascriptChannels: Set.from([
JavascriptChannel(
name: 'Print',
onMessageReceived: (JavascriptMessage message) {
//This is where you receive message from
//javascript code and handle in Flutter/Dart
//like here, the message is just being printed
//in Run/LogCat window of android studio
print(message.message);
})
]),
onWebViewCreated: (WebViewController w) {
webViewController = w;
},
)
and in Your HTMLfile:
<script type='text/javascript'>
Print.postMessage('Hello World being called from Javascript code');
</script>
When you run this code, you shall be able to see log "Hello World being called from Javascript code" in the LogCat/Run window of android studio.

You can try my plugin flutter_inappbrowser (EDIT: it has been renamed to flutter_inappwebview) and use addJavaScriptHandler({#required String handlerName, #required JavaScriptHandlerCallback callback}) method (see more here).
An example is presented below.
On Flutter side:
...
child: InAppWebView(
initialFile: "assets/index.html",
initialHeaders: {},
initialOptions: InAppWebViewWidgetOptions(
inAppWebViewOptions: InAppWebViewOptions(
debuggingEnabled: true,
)
),
onWebViewCreated: (InAppWebViewController controller) {
webView = controller;
controller.addJavaScriptHandler(handlerName: "mySum", callback: (args) {
// Here you receive all the arguments from the JavaScript side
// that is a List<dynamic>
print("From the JavaScript side:");
print(args);
return args.reduce((curr, next) => curr + next);
});
},
onLoadStart: (InAppWebViewController controller, String url) {
},
onLoadStop: (InAppWebViewController controller, String url) {
},
onConsoleMessage: (InAppWebViewController controller, ConsoleMessage consoleMessage) {
print("console message: ${consoleMessage.message}");
},
),
...
On JavaScript side (for example a local file assets/index.html inside the assets folder):
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Flutter InAppBrowser</title>
...
</head>
<body>
...
<script>
// In order to call window.flutter_inappwebview.callHandler(handlerName <String>, ...args)
// properly, you need to wait and listen the JavaScript event flutterInAppWebViewPlatformReady.
// This event will be dispatched as soon as the platform (Android or iOS) is ready to handle the callHandler method.
window.addEventListener("flutterInAppWebViewPlatformReady", function(event) {
// call flutter handler with name 'mySum' and pass one or more arguments
window.flutter_inappwebview.callHandler('mySum', 12, 2, 50).then(function(result) {
// get result from Flutter side. It will be the number 64.
console.log(result);
});
});
</script>
</body>
</html>
On Android Studio logs you will get:
I/flutter (20436): From JavaScript side:
I/flutter (20436): [12, 2, 50]
I/flutter (20436): console message: 64

I want to tell you about how to send messages from flutter WebView to JS:
In JS code you need to bind your function you need to fire to window
const function = () => alert('hello from JS');
window.function = function;
In your code in WebView widget implementation you need to declare onWebViewCreated method like this
WebView(
onWebViewCreated: (WebViewController controller) {},
initialUrl: 'https://url.com',
javascriptMode: JavascriptMode.unrestricted,
)
In class widget declare var _webViewController;
class App extends State<MyApp> {
final _webViewController;
}
In onWebViewCreated write this code
onWebViewCreated: (WebViewController controller) {
_webViewController = controller;
},
Then you can run code like this:
class App extends StatelessWidget {
var _webViewController;
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
home: Scaffold(
body: WebView(
onWebViewCreated: (WebViewController controller) {
_webViewController = controller;
},
initialUrl: 'https://url.com',
javascriptMode: JavascriptMode.unrestricted,
),
floatingActionButton: FloatingActionButton(
onPressed: () {
// When you click at this button youll run js code and youll see alert
_webViewController
.evaluateJavascript('window.function ()');
},
child: Icon(Icons.add),
backgroundColor: Colors.green,
),
),
);
}
}
But what if we want to share this _webViewController instance to other widgets like drawer?
In this case I decided to implement Singleton pattern and store _webViewController instance in it.
So
Singleton class
class Singleton {
WebViewController webViewController;
static final Singleton _singleton = new Singleton._internal();
static Singleton get instance => _singleton;
factory Singleton(WebViewController webViewController) {
_singleton.webViewController = webViewController;
return _singleton;
}
Singleton._internal();
}
Then
onWebViewCreated: (WebViewController controller) {
var singleton = new Singleton(controller);
},
And finally in our Drawer widget i.e. (here you can use whatever widget you want)
class EndDrawer extends StatelessWidget {
final singleton = Singleton.instance;
#override
Widget build(BuildContext context) {
return Drawer(
child: Column(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
SizedBox(
width: 200,
child: FlatButton(
onPressed: () {
singleton.webViewController.evaluateJavascript('window.function()');
Navigator.pop(context); // exit drawer
},
child: Row(
children: <Widget>[
Icon(
Icons.exit_to_app,
color: Colors.redAccent,
),
SizedBox(
width: 30,
),
Text(
'Exit',
style: TextStyle(color: Colors.blueAccent, fontSize: 20),
),
],
),
)),
],
),
);
}
}
If you want to receive messages from JS code to your flutter App you need:
In your js code
window.CHANNEL_NAME.postMessage('Hello from JS');
In your flutter code.
When you're running JavascriptChannel(name: 'CHANNEL_NAME', ...)
flutter bind to your window WebView new MessageChannel with name you wrote in constructor (in this case CHANNEL_NAME)
so when we call window.CHANNEL_NAME.postMessage('Hello from JS'); we recieve a message we sent
WebView(
javascriptChannels: [
JavascriptChannel(name: 'CHANNEL_NAME', onMessageReceived: (message) {
print(message.message);
})
].toSet(),
initialUrl: 'https://url.com',
)
So here we are.
I'm new in flutter code
So if you have another better experience about this you can write in comments to help other people!

Full code example of Javascript callbacks using package flutter_inappwebview:
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter_inappwebview/flutter_inappwebview.dart';
Future main() async {
WidgetsFlutterBinding.ensureInitialized();
runApp(new MyApp());
}
class MyApp extends StatefulWidget {
#override
_MyAppState createState() => new _MyAppState();
}
class _MyAppState extends State<MyApp> {
InAppWebViewController _webViewController;
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: const Text('InAppWebView Example'),
),
body: Container(
child: Column(children: <Widget>[
Expanded(
child: InAppWebView(
initialData: InAppWebViewInitialData(data: """
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
</head>
<body>
<h1>JavaScript Handlers (Channels) TEST</h1>
<button id='test' onclick="window.flutter_inappwebview.callHandler('testFunc');">Test</button>
<button id='testargs' onclick="window.flutter_inappwebview.callHandler('testFuncArgs', 1);">Test with Args</button>
<button id='testreturn' onclick="window.flutter_inappwebview.callHandler('testFuncReturn').then(function(result) { alert(result);});">Test Return</button>
</body>
</html>
"""),
initialOptions: InAppWebViewGroupOptions(
crossPlatform: InAppWebViewOptions(
debuggingEnabled: true,
)),
onWebViewCreated: (InAppWebViewController controller) {
_webViewController = controller;
_webViewController.addJavaScriptHandler(
handlerName: 'testFunc',
callback: (args) {
print(args);
});
_webViewController.addJavaScriptHandler(
handlerName: 'testFuncArgs',
callback: (args) {
print(args);
});
_webViewController.addJavaScriptHandler(
handlerName: 'testFuncReturn',
callback: (args) {
print(args);
return '2';
});
},
onConsoleMessage: (controller, consoleMessage) {
print(consoleMessage);
},
),
),
])),
),
);
}
}

There are two ways to communicate the answer:
First way From Flutter to the webview (javascript, react...)
From the flutter side (using a button or in a trigger method):
webViewController.evaluateJavascript('fromFlutter("pop")');
This fromFlutter will be the name of the method in your javascript, react, whatever and also you can send text, in this case "pop".
From the javascript side inside the html, in your body label:
<script type="text/javascript">
function fromFlutter(data) {
// Do something
console.log("This is working now!!!");
}
</script>
Second way From your webview (javascript, react...) to Flutter
In your Webview attribute javascriptChannels you can add:
javascriptChannels: Set.from([
JavascriptChannel(
name: 'comunicationname',
onMessageReceived: (JavascriptMessage message) async {
// Here you can take message.message and use
// your string from webview
},
)
]),
From the webview using the same communication name "communicationname" (your can use another name in both places):
window.communicationname.postMessage("native,,,pop,");

Flutter 3.0.5
webview_flutter: ^3.0.4
flutter_js: ^0.5.0+6
Another way to use JavascriptChannels is to tranfer data from the "App" to your Website.
Dart:
JavascriptChannel(
name: 'getFCMToken',
onMessageReceived: (JavascriptMessage message) async {
//print(message.message);
final token = (await FirebaseMessaging.instance.getToken())!;
final script = "var appToken =\"${token }\"";
_webViewController.runJavascript(script);
},
),
html:
<script type = "text/javascript">
window.onload = getFCMToken.postMessage('');
</script>
or Dart(Trigger):
OnPageFinished: (url) async {
try {
final token = (await FirebaseMessaging.instance.getToken())!;
var javascript = "var appToken=\"${token.toString()}\"";
} catch (_) {}
}
so in your website code you have a js var "appToken" wich you can use in PHP or whatever.

If you are using webviewx plugin which support web,ios and android than this is how we can do two way communication.
I have webpage which has index.html and other js,and css pages which I want to display in webview and communicate between flutter and web app.
1. From flutter to js listener
IconButton(
icon: Icon(Icons.developer_mode),
onPressed: () {
webviewController
.evalRawJavascript('window.myFunction()',
inGlobalContext: false)
.then((value) => print(value));
},
)
Note: myFunction is function defined in javascript or html page as below.
function myFunction() {
alert("I am an alert box!");
return 'working';
}
2. From js/html to flutter listener
In html/js add button with listener
function submitClick() {
var data = document.getElementById('data').value;
SubmitCallback(data) //defined in flutter
}
Now In flutter(add dartCallback):
WebViewX(
javascriptMode: JavascriptMode.unrestricted,
initialContent: '<h2> Loading </h2>',
initialSourceType: SourceType.HTML,
onWebViewCreated: (controller) {
webviewController = controller;
_loadHtmlFromAssets();
webviewController.addListener(() {});
},
dartCallBacks: {
DartCallback(
name: 'SubmitCallback',
callBack: (msg) {
ScaffoldMessenger.of(context).showSnackBar(
SnackBar(content: Text('Submitted $msg successfully')));
},
),
},
)
PS. Happy Coding