flutter_webview_plugin/lib/src/base.dart

import 'dart:async';
import 'dart:ui';

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

const _kChannel = 'flutter_webview_plugin';

// TODO: more general state for iOS/android
enum WebViewState { shouldStart, startLoad, finishLoad }

// TODO: use an id by webview to be able to manage multiple webview

/// Singleton Class that communicate with a Webview Instance
/// Have to be instanciate after `runApp` called.
class FlutterWebviewPlugin {
  final _channel = const MethodChannel(_kChannel);

  final _onDestroy = new StreamController<Null>.broadcast();
  final _onUrlChanged = new StreamController<String>.broadcast();
  final _onStateChanged = new StreamController<WebViewStateChanged>.broadcast();
  final _onError = new StreamController<String>.broadcast();

  static FlutterWebviewPlugin _instance;

  factory FlutterWebviewPlugin() => _instance ??= new FlutterWebviewPlugin._();

  FlutterWebviewPlugin._() {
    _channel.setMethodCallHandler(_handleMessages);
  }

  Future<Null> _handleMessages(MethodCall call) async {
    switch (call.method) {
      case "onDestroy":
        _onDestroy.add(null);
        break;
      case "onUrlChanged":
        _onUrlChanged.add(call.arguments["url"]);
        break;
      case "onState":
        _onStateChanged.add(
          new WebViewStateChanged.fromMap(
              new Map<String, dynamic>.from(call.arguments)),
        );
        break;
      case "onError":
        _onError.add(call.arguments);
        break;
    }
  }

  /// Listening the OnDestroy LifeCycle Event for Android
  Stream<Null> get onDestroy => _onDestroy.stream;

  /// Listening url changed
  Stream<String> get onUrlChanged => _onUrlChanged.stream;

  /// Listening the onState Event for iOS WebView and Android
  /// content is Map for type: {shouldStart(iOS)|startLoad|finishLoad}
  /// more detail than other events
  Stream<WebViewStateChanged> get onStateChanged => _onStateChanged.stream;

  /// Start the Webview with [url]
  /// - [withJavascript] enable Javascript or not for the Webview
  ///     iOS WebView: Not implemented yet
  /// - [clearCache] clear the cache of the Webview
  /// - [clearCookies] clear all cookies of the Webview
  /// - [hidden] not show
  /// - [rect]: show in rect, fullscreen if null
  /// - [enableAppScheme]: false will enable all schemes, true only for httt/https/about
  ///     android: Not implemented yet
  /// - [userAgent]: set the User-Agent of WebView
  /// - [withZoom]: enable zoom on webview
  /// - [withLocalStorage] enable localStorage API on Webview
  ///     Currently Android only.
  ///     It is always enabled in UIWebView of iOS and  can not be disabled.
  /// - [withLocalUrl]: allow url as a local path
  ///     Allow local files on iOs > 9.0
  /// - [scrollBar]: enable or disable scrollbar
  Future<Null> launch(String url,
      {bool withJavascript,
      bool clearCache,
      bool clearCookies,
      bool hidden,
      bool enableAppScheme,
      Rect rect,
      String userAgent,
      bool withZoom,
      bool withLocalStorage,
      bool withLocalUrl,
      bool scrollBar}) async {
    Map<String, dynamic> args = {
      "url": url,
      "withJavascript": withJavascript ?? true,
      "clearCache": clearCache ?? false,
      "hidden": hidden ?? false,
      "clearCookies": clearCookies ?? false,
      "enableAppScheme": enableAppScheme ?? true,
      "userAgent": userAgent,
      "withZoom": withZoom ?? false,
      "withLocalStorage": withLocalStorage ?? true,
      "withLocalUrl": withLocalUrl ?? false,
      "scrollBar": scrollBar ?? true
    };
    if (rect != null) {
      args["rect"] = {
        "left": rect.left,
        "top": rect.top,
        "width": rect.width,
        "height": rect.height
      };
    }
    await _channel.invokeMethod('launch', args);
  }

  /// Execute Javascript inside webview
  Future<String> evalJavascript(String code) async {
    final res = await _channel.invokeMethod('eval', {"code": code});
    return res;
  }

  /// Close the Webview
  /// Will trigger the [onDestroy] event
  Future close() => _channel.invokeMethod("close");

  /// Reloads the WebView.
  /// This is only available on Android for now.
  Future reload() => _channel.invokeMethod("reload");

  /// Navigates back on the Webview.
  /// This is only available on Android for now.
  Future goBack() => _channel.invokeMethod("back");

  /// Navigates forward on the Webview.
  /// This is only available on Android for now.
  Future goForward() => _channel.invokeMethod("forward");

  /// Close all Streams
  void dispose() {
    _onDestroy.close();
    _onUrlChanged.close();
    _onStateChanged.close();
    _onError.close();
    _instance = null;
  }

  Future<Map<String, dynamic>> getCookies() async {
    final cookiesString = await evalJavascript("document.cookie");
    final cookies = {};

    if (cookiesString?.isNotEmpty == true) {
      cookiesString.split(";").forEach((String cookie) {
        final splited = cookie.split("=");
        cookies[splited[0]] = splited[1];
      });
    }

    return cookies;
  }

  /// resize webview
  Future<Null> resize(Rect rect) async {
    final args = {};
    args["rect"] = {
      "left": rect.left,
      "top": rect.top,
      "width": rect.width,
      "height": rect.height
    };
    await _channel.invokeMethod('resize', args);
  }
}

class WebViewStateChanged {
  final WebViewState type;
  final String url;
  final int navigationType;

  WebViewStateChanged(this.type, this.url, this.navigationType);

  factory WebViewStateChanged.fromMap(Map<String, dynamic> map) {
    WebViewState t;
    switch (map["type"]) {
      case "shouldStart":
        t = WebViewState.shouldStart;
        break;
      case "startLoad":
        t = WebViewState.startLoad;
        break;
      case "finishLoad":
        t = WebViewState.finishLoad;
        break;
    }
    return new WebViewStateChanged(t, map["url"], map["navigationType"]);
  }
}