How to load a local html file in Flutter WebView

In my previous flutter code example, I went through how to create simple flutter webview. In the code example, we displayed a remote website (inducesmile.com) which worked perfectly well.

But there are also when we will need to load locally stored html file in assets folder into flutter webview.

Loading locally stored html file in flutter might be more involved to loading a remote web page in flutter webview.

So in this flutter code example, we will explore how to load a local html file in flutter webview.

Feel free to use the flutter code in your project. You can as well customize it to suit your project requirement. No need to revert the wheel.

If you make huge modification or you have alternative solution you will like to share with our community, kindly us the comment box below.

1. Add flutter_webview plugin in pubspec.yaml

name: flutter_app
description: A new Flutter application.

# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# Read more about versioning at semver.org.
version: 1.0.0+1

environment:
  sdk: ">=2.0.0-dev.68.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.2
  http: 0.12.0
  ##sqflite: 0.13.0+1
  path_provider: 0.4.1
  ##zoomable_image: 1.2.1+1
  ##multi_image_picker: 2.3.32
  dio: 2.0.22
  shared_preferences: 0.4.3
  flare_flutter: any
  flutter_webview_plugin: 0.3.0+2
  webview_flutter: 0.2.0


dev_dependencies:
  flutter_test:
    sdk: flutter


# For information on the generic Dart part of this file, see the
# following page: https://www.dartlang.org/tools/pub/pubspec

# The following section is specific to Flutter.
flutter:

  # The following line ensures that the Material Icons font is
  # included with your application, so that you can use the icons in
  # the material Icons class.
  uses-material-design: true

  assets:
    - assets/html_code.html
    - assets/iframe.html
    - assets/js_lib.html


  # To add assets to your application, add an assets section, like this:
  # assets:
  #  - images/a_dot_burr.jpeg
  #  - images/a_dot_ham.jpeg

  # An image asset can refer to one or more resolution-specific "variants", see
  # https://flutter.io/assets-and-images/#resolution-aware.

  # For details regarding adding assets from package dependencies, see
  # https://flutter.io/assets-and-images/#from-packages

  # To add custom fonts to your application, add a fonts section here,
  # in this "flutter" section. Each entry in this list should have a
  # "family" key with the font family name, and a "fonts" key with a
  # list giving the asset and other descriptors for the font. For
  # example:
  # For details regarding fonts from package dependencies,
  # see https://flutter.io/custom-fonts/#from-packages

2. Create main.dart if it does not already exist

This is the entry point of our application. Open the file and add the code below.

import 'package:flutter/material.dart';
import 'load_html_file_task-4.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: LoadHTMLFileToWEbView(),
    );
  }
}

In the above code, we have the load_html_file_task-4.dartfile. This file is where we will add our simple flutter webview widget class

3. Create load_html_file_task-4.dart in lib folder

Create a new dart file in the lib folder. I have named it load_html_file_task.dart but can use a name of your choice.

Since loading and reading a local file can block the main thread, we are going to use flutter FutureBuilder()and Future class to perform async execution.

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_webview_plugin/flutter_webview_plugin.dart';
import 'dart:async';

class LoadHTMLFileToWEbView extends StatefulWidget {
  @override
  _LoadHTMLFileToWEbViewState createState() => _LoadHTMLFileToWEbViewState();
}

class _LoadHTMLFileToWEbViewState extends State<LoadHTMLFileToWEbView> {
  @override
  Widget build(BuildContext context) {
    return FutureBuilder<String>(
      future: _loadLocalHTML(),
      builder: (context, snapshot) {
        if (snapshot.hasData) {
          return WebviewScaffold(
            appBar: AppBar(title: Text("Load HTM file in WebView")),
            withJavascript: true,
            appCacheEnabled: true,
            url: new Uri.dataFromString(snapshot.data, mimeType: 'text/html')
                .toString(),
          );
        } else if (snapshot.hasError) {
          return Scaffold(
            body: Center(
              child: Text("${snapshot.error}"),
            ),
          );
        }
        return Scaffold(
          body: Center(child: CircularProgressIndicator()),
        );
      },
    );
  }
}

Future<String> _loadLocalHTML() async {
  return await rootBundle.loadString('assets/html_code.html');
}

4. Run your app

You can use flutter command to run your app – $ flutter run

If everything goes well, you will see a website similar to the image below in your flutter webview.

If you have any question or suggestions kindly use the comment box or you can contact us directly through our contact page below.

 

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