Add a method to get the title of the current page as soon as it's available

[cremor]

Use case

I'd like to show the title of the current page in the AppBar. The title should be shown as soon as it's available, not only when the page has finished loading.

I know about the usual workaround to use evalJavascript('document.title') that is recommended in other issues like #30 and #192. But that isn't enough for two reasons:

1. evalJavaScript doesn't work on Android SDK versions below 19.
2. evalJavaScript must be run after the page has finished loading.

Proposal

Add a method that returns the title from the WebView. You can use WebView.getTitle() on Android and WKWebView.title on iOS to get it.

To know when the title is available, Android offers WebChromeClient.onReceivedTitle(). This should be forwarded to a new event on FlutterWebviewPlugin. I don't know if there is something similar for iOS.

[korchix]

Hi, actually the Webview provides already a good solution to this, like mentioned in the issue #30 but with the onStateChanged listener and not the onUrlChanged listener mentioned there.
so the code should be something like this:

String webViewTitle = "";
....

flutterWebviewPlugin.onStateChanged.listen((WebViewStateChanged st) async {
   String currentWebviewTitle = await flutterWebviewPlugin.evalJavascript("window.document.title");
   setState(() => {webViewTitle = currentWebviewTitle});
});

...

new WebviewScaffold(
              url: "https://www.google.com",
              appBar: new AppBar(
                title: new Text(webviewTitle),
              ),
            );

i just tested it with an iPhone X (real device, not an emulator) and it works.