WebViews in Flutter - Does it really work?

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   WebViews in Flutter Lara Martín @lariki Does it really work?

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   What is a WebView?

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   Why we need WebViews? Perform social login Show static content

   (e.g. FAQ ) Payment confirmation Use cases Making an app that is just a web Avoid for
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   https:/ /pub.dev/packages/webview_flutter

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   Setup # pubspec.yaml dependencies: flutter: sdk: flutter webview_flutter: ^0.3.6

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   Implementation • Not reimplemented in Dart! • Uses native WebView

   • iOS: WKWebView • Android: android.webkit.WebView • But is it a Widget? • The plugin creates the native WebView • And renders it in Flutter!
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   Working Example

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   Rendering the Android WebView

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   Flutter Inspector

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    Flutter Inspector

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    Flutter Inspector

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    WebView Rendering on Android

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    WebView WebView Rendering on Android

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    AndroidView WebView child WebView Rendering on Android

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    WebView Rendering on Android AndroidView WebView WebViewFlutterPlugin child requires …

    WebViewFactory registers
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    AndroidView WebView FlutterWebView : PlatformView WebView contains creates child …

    WebView Rendering on Android WebViewFlutterPlugin requires WebViewFactory registers
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    AndroidView WebView FlutterWebView : PlatformView WebView PlatformViewController contains creates renders

    Surface child … in WebView Rendering on Android WebViewFlutterPlugin requires WebViewFactory registers
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    AndroidView _AndroidPlatformView RenderAndroidView : RenderBox WebView FlutterWebView : PlatformView WebView

    PlatformViewController contains creates renders Surface contains contains child … in WebView Rendering on Android WebViewFlutterPlugin requires WebViewFactory registers
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    AndroidView _AndroidPlatformView RenderAndroidView : RenderBox WebView FlutterWebView : PlatformView WebView

    PlatformViewController contains creates renders Surface contains contains child … in WebView Rendering on Android WebViewFlutterPlugin requires WebViewFactory registers Surface ID
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    Rendering the iOS WKWebView

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    WebView Rendering on iOS • Similar to Android • RenderUiKitView

    will render a surface created in the PlatformViewIOS • Passes an ID
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    WebView Widget

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    WebView Widget • initialUrl • javaScriptMode • onWebViewCreated • onPageFinished

    • gestureRecognizers • navigationDelegate • javaScriptChannels
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    WebView Widget • initialUrl • javaScriptMode • onWebViewCreated • onPageFinished

    • gestureRecognizers • navigationDelegate • javaScriptChannels
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    WebView Widget: initialUrl WebView( ),

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    WebView Widget: initialUrl WebView( initialUrl: “https://www.flutter.dev/", ),

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    WebView Widget • initialUrl • javaScriptMode • onWebViewCreated • onPageFinished

    • gestureRecognizers • navigationDelegate • javaScriptChannels
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    WebView Widget: javaScriptMode WebView( initialUrl: … javascriptMode: JavascriptMode.unrestricted, ),

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    WebView Widget • initialUrl • javaScriptMode • onWebViewCreated • onPageFinished

    • gestureRecognizers • navigationDelegate • javaScriptChannels
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    WebView Widget: onWebViewCreated WebView( initialUrl: … javascriptMode: … onWebViewCreated: (WebViewController

    controller) { _controller = controller; }, ),
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    WebViewController • loadUrl(String url) • currentUrl() • canGoBack() • canGoForward()

    • goBack() • goForward() • reload() • clearCache()
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    WebViewController • loadUrl(String url) • currentUrl() • canGoBack() • canGoForward()

    • goBack() • goForward() • reload() • clearCache()
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    WebViewController: reload onPressed: () async { await _controller.reload(); }

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    WebView Widget • initialUrl • javaScriptMode • onWebViewCreated • onPageFinished

    • gestureRecognizers • navigationDelegate • javaScriptChannels
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    WebView Widget: onPageFinished WebView( initialUrl: … javascriptMode: … onWebViewCreated: …

    onPageFinished: (url) { // use the URL } )
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    WebView Widget • initialUrl • javaScriptMode • onWebViewCreated • onPageFinished

    • gestureRecognizers • navigationDelegate • javaScriptChannels The Power of WebViews in Flutter, by Emily Fortuna https:/ /medium.com/flutter-io/the-power-of- webviews-in-flutter-a56234b57df2
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    WebView Widget • initialUrl • javaScriptMode • onWebViewCreated • onPageFinished

    • gestureRecognizers • navigationDelegate • javaScriptChannels
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    NavigationDelegate typedef NavigationDecision NavigationDelegate(NavigationRequest n);

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    NavigationDelegate WebView( navigationDelegate: (request) { bool isHost = request.url.startsWith( “https://flutter.dev”);

    if (isHost) return NavigationDecision.navigate; else return NavigationDecision.prevent; } ),
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    WebView Widget • initialUrl • javaScriptMode • onWebViewCreated • onPageFinished

    • gestureRecognizers • navigationDelegate • javaScriptChannels
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    javaScriptChannels WebView( javascriptChannels: {_channel}, ),

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    javaScriptChannels var _channel = JavascriptChannel( name: 'LaraDemo', onMessageReceived: (JavascriptMessage message)

    { print(message.message); }); WebView( javascriptChannels: {_channel}, ),
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    javaScriptChannels var _channel = JavascriptChannel( name: 'LaraDemo', onMessageReceived: (JavascriptMessage message)

    { print(message.message); }); Flutter side <script> LaraDemo.postMessage('Hello'); </script> HTML side
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    Limitations

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    Input Fields https:/ /github.com/flutter/flutter/issues/19718

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    Text Selection https:/ /github.com/flutter/flutter/issues/24584

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    Performance AndroidView is costly

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    What’s next

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    Loading an HTML string https:/ /github.com/flutter/plugins/pull/1312

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    Setting a custom UserAgent https:/ /github.com/flutter/plugins/pull/968

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    Page loaded correctly https:/ /github.com/flutter/plugins/pull/1389

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    Contributing

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    Contributing

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    Flutter is open-source. Submit a pull request!

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    Thanks. @lariki Lara Martín