migrate to package:web and implement keyboard detection

flutter_keyboard_visibility_web/lib/flutter_keyboard_visibility_web.dart

@@ -1,25 +1,46 @@
-import 'dart:html' as html show window, Navigator;
+import 'dart:async';
+import 'package:web/web.dart' as html;
 import 'package:flutter_keyboard_visibility_platform_interface/flutter_keyboard_visibility_platform_interface.dart';
 import 'package:flutter_web_plugins/flutter_web_plugins.dart';
 
 /// The web implementation of the [FlutterKeyboardVisibilityPlatform] of the
 /// FlutterKeyboardVisibility plugin.
-class FlutterKeyboardVisibilityPluginWeb
-    extends FlutterKeyboardVisibilityPlatform {
+class FlutterKeyboardVisibilityPluginWeb extends FlutterKeyboardVisibilityPlatform {
   /// Constructs a [FlutterKeyboardVisibilityPluginWeb].
   FlutterKeyboardVisibilityPluginWeb(html.Navigator navigator);
 
+  static final _onChangeController = StreamController<bool>();
+  static final _onChange = _onChangeController.stream.asBroadcastStream();
+
   /// Factory method that initializes the FlutterKeyboardVisibility plugin
   /// platform with an instance of the plugin for the web.
   static void registerWith(Registrar registrar) {
-    FlutterKeyboardVisibilityPlatform.instance =
-        FlutterKeyboardVisibilityPluginWeb(html.window.navigator);
+    FlutterKeyboardVisibilityPlatform.instance = FlutterKeyboardVisibilityPluginWeb(html.window.navigator);
+    html.EventStreamProvider<html.Event>('resize').forTarget(html.window.visualViewport).listen((e) {
+      final minKeyboardHeight = 200;
+
+      final screenHeight = html.window.screen.height;
+      final viewportHeight = html.window.visualViewport?.height.toInt() ?? 0;
+      final newState = (screenHeight - minKeyboardHeight) > viewportHeight;
+      _updateValue(newState);
+    });
+  }
+
+  static bool get isVisible => _isVisible;
+  static bool _isVisible = false;
+
+  static void _updateValue(bool newValue) {
+    // Don't report the same value multiple times
+    if (newValue == _isVisible) {
+      return;
+    }
+
+    _isVisible = newValue;
+    _onChangeController.add(newValue);
   }
 
   /// Emits changes to keyboard visibility from the platform. Web is not
   /// implemented yet so false is returned.
   @override
-  Stream<bool> get onChange async* {
-    yield false;
-  }
+  Stream<bool> get onChange => _onChange;
 }

flutter_keyboard_visibility_web/pubspec.yaml

@@ -5,7 +5,7 @@ homepage: https://github.com/MisterJimson/flutter_keyboard_visibility
 repository: https://github.com/MisterJimson/flutter_keyboard_visibility
 
 environment:
-  sdk: '>=2.12.0 <4.0.0'
+  sdk: ">=2.12.0 <4.0.0"
   flutter: ">=1.20.0"
 
 flutter:
@@ -17,6 +17,7 @@ flutter:
 
 dependencies:
   flutter_keyboard_visibility_platform_interface: ^2.0.0
+  web: ^0.5.0
   flutter_web_plugins:
     sdk: flutter
   flutter:
@@ -25,4 +26,4 @@ dependencies:
 dev_dependencies:
   pedantic: ^1.11.0
   flutter_test:
-    sdk: flutter
+    sdk: flutter