WebView support for FlutterWeb for plugin development

Issue

Hi I developed a Flutter Plugin flutter_tex. It’s based on the WebView. How do I add Flutter Web support for this??

I tried this example to show my HTML content.

import 'dart:ui' as ui;

  void forWeb() {
    if(kIsWeb){
      // ignore: undefined_prefixed_name
      ui.platformViewRegistry.registerViewFactory(
          'hello-world-html',
              (int viewId) => uni_html.IFrameElement()
            ..width = '640'
            ..height = '360'
            ..src = 'https://www.youtube.com/embed/IyFZznAk69U'
            ..style.border = 'none');

      Directionality(
        textDirection: TextDirection.ltr,
        child: Center(
          child: SizedBox(
            width: 200,
            height: 200,
            child: HtmlElementView(viewType: 'hello-world-html'),
          ),
        ),
      );
    }
  }

But this code is fine when building for the web but when for compiling on android I get this error even if I am not calling above code.

Compiler message:
../lib/flutter_tex.dart:139:10: Error: Getter not found: 'platformViewRegistry'.
      ui.platformViewRegistry.registerViewFactory(
         ^^^^^^^^^^^^^^^^^^^^
Target kernel_snapshot failed: Exception: Errors during snapshot creation: null
build failed.

FAILURE: Build failed with an exception.

Solution

You can copy paste run 3 files below main.dart , mobileui.dart and webui.dart
You can put mobile and web code in different files and use conditional import
This allow you to have different implement on mobile and web

import 'mobileui.dart' if (dart.library.html) 'webui.dart' as multiPlatform;
...
home:  multiPlatform.TestPlugin(),

working demo
when run with Chrome or Android Emulator in Android Studio

enter image description here
enter image description here

main.dart

import 'package:flutter/material.dart';
import 'mobileui.dart' if (dart.library.html) 'webui.dart' as multiPlatform;

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

class MyApp extends StatelessWidget { 
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(        
        primarySwatch: Colors.blue,
      ),
      home:  multiPlatform.TestPlugin(),
    );
  }
}

mobileui.dart

import 'package:flutter/material.dart';

class TestPlugin extends StatefulWidget {
  @override
  _TestPluginState createState() => _TestPluginState();
}

class _TestPluginState extends State<TestPlugin> {
  @override
  Widget build(BuildContext context) {
    return Text("Mobile");
  }
}

webui.dart

import 'package:flutter/material.dart';
import 'dart:html' as html;
import 'dart:js' as js;
import 'dart:ui' as ui;


class TestPlugin extends StatefulWidget {
  TestPlugin();

  _TestPluginState createState() => _TestPluginState();
}

class _TestPluginState extends State<TestPlugin> {
  String createdViewId = 'map_element';

  @override
  void initState() {
    // ignore: undefined_prefixed_name
    ui.platformViewRegistry.registerViewFactory(
        createdViewId,
            (int viewId) => html.IFrameElement()
          ..width = MediaQuery.of(context).size.width.toString() //'800'
          ..height = MediaQuery.of(context).size.height.toString() //'400'
          ..srcdoc = """<!DOCTYPE html><html>
          <head><title>Page Title</title></head><body><h1>This is a Heading</h1><p>This is a paragraph.</p></body></html>"""            
          ..style.border = 'none');

    super.initState();
  }

  @override
  void dispose() {
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
        padding: EdgeInsets.symmetric(horizontal: 10),
        decoration: BoxDecoration(
            color: Colors.white,
            border: Border.all(color: Colors.grey[300], width: 1),
            borderRadius: BorderRadius.all(Radius.circular(5))),
        width: 200,
        height: 200,
        child: Directionality(
            textDirection: TextDirection.ltr,
            child: HtmlElementView(
              viewType: createdViewId,
            )));
  }
}

Answered By – chunhunghan

Answer Checked By – Terry (FlutterFixes Volunteer)

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