如何在单击按钮时使用颤动的 webview 返回上一页？

Question

我想使用webview_flutter 构建一个简单的应用程序，不使用AppBar，使用静态URL，只需在屏幕底部使用一个简单的floatingActionButton 即可导航到上一页，但我没有知道该怎么做。

谁能给我一些指导，以便我可以尝试让按钮做它应该做的事情？

这是带有按钮的应用图片：

我不知道该尝试什么，但我正在努力学习，抱歉=D

这是我的全部代码： =)

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

void main () {
  runApp(MaterialApp(
    title: 'Something',
    home: AplicativoB2b(),
    debugShowCheckedModeBanner: false,
  ));
  SystemChrome.setEnabledSystemUIOverlays ([]);
}

class AplicativoB2b extends StatefulWidget {
  @override
  _AplicativoB2bState createState() => _AplicativoB2bState();
}

class _AplicativoB2bState extends State<AplicativoB2b> {

  Completer<WebViewController> _controller = Completer<WebViewController>();

  @override
  Widget build(BuildContext context) {

    return Scaffold(
      body: WebView(
        initialUrl: 'https://google.com',
        javascriptMode: JavascriptMode.unrestricted,
        onWebViewCreated: (WebViewController webViewController) {
           _controller.complete(webViewController);
        },
      ),
      floatingActionButton: FloatingActionButton(
              onPressed: () {
               //HELP ME HERE!! =(
              },
              child: const Icon(Icons.arrow_back),
              backgroundColor: Colors.black,
            ),
      // bottomNavigationBar: BottomAppBar(color: Colors.white, child: Container(height: 50.0),),
      // floatingActionButtonLocation: FloatingActionButtonLocation.endDocked,
      );
  }
}

Answer 1

Future<bool> _willPopCallback() async {
    WebViewController webViewController = await _controller.future;
    bool canNavigate = await webViewController.canGoBack();
    if (canNavigate) {
      webViewController.goBack();
      return false;
    } else {
      return true;
    }
  }

Answer 2

我使用的代码与上一个答案不同。我按照this 教程让 webview 和浮动按钮工作。从那里，很容易给浮动按钮一个后退箭头图标，并在单击浮动按钮时让 web 视图返回一个页面。

当点击浮动按钮时让webview返回一个页面（把它放在它的onpressed方法中）：

 controller.data.goBack();

浮动按钮的图标可以在这行代码中轻松更改：

child: Icon(Icons.arrow_back)

所有不同的按钮都可以在这里找到：link

这是我所有的代码：

import 'package:flutter/material.dart';
import 'package:webview_flutter/webview_flutter.dart';
import 'dart:async';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'App',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'App'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final Completer<WebViewController> _controller = Completer<WebViewController>();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: WebView(
        initialUrl: "https://google.com",
        javascriptMode: JavascriptMode.unrestricted,
        onWebViewCreated: (WebViewController webViewController) {
          _controller.complete(webViewController);
        },
      ),
      floatingActionButton: FutureBuilder<WebViewController>(
        future: _controller.future,
        builder: (BuildContext context, 
          AsyncSnapshot<WebViewController> controller) {
            if (controller.hasData) {
              return FloatingActionButton(
                child: Icon(Icons.arrow_back),
                onPressed: () {
                  controller.data.goBack();
                });
            }

            return Container();
          }
        ),
    );
  }
}

Answer 3

我做到了！ =D

对很多人来说可能看起来很简单哈哈，但是对于以前从未接触过这种东西的人来说，我为我的忍者 Ctrl C + Ctrl V 感到非常自豪。开玩笑，我看了很多例子并尝试了这很有效，如果有人有任何建议，我会很感激！ =)

这就是我所做的：

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

void main () {
  runApp(MaterialApp(
    title: 'Something',
    home: AplicativoB2b(),
    debugShowCheckedModeBanner: false,
  ));
  SystemChrome.setEnabledSystemUIOverlays ([]);
}

class AplicativoB2b extends StatefulWidget {
  @override
  _AplicativoB2bState createState() => _AplicativoB2bState();
}

class _AplicativoB2bState extends State<AplicativoB2b> {

  Completer<WebViewController> _controller = Completer<WebViewController>();

  @override
  Widget build(BuildContext context) {

    return Scaffold(
      body: WebView(
        initialUrl: 'https://google.com',
        javascriptMode: JavascriptMode.unrestricted,
        onWebViewCreated: (WebViewController webViewController) {
           _controller.complete(webViewController);
        },
      ),
      floatingActionButton: NavigationControls(_controller.future), // <-- added this
      );
  }
}

还有我用于floatingActionButton 的类。

class NavigationControls extends StatelessWidget {
  const NavigationControls(this._webViewControllerFuture)
      : assert(_webViewControllerFuture != null);

  final Future<WebViewController> _webViewControllerFuture;

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<WebViewController>(
      future: _webViewControllerFuture,
      builder:
          (BuildContext context, AsyncSnapshot<WebViewController> snapshot) {
        final bool webViewReady =
            snapshot.connectionState == ConnectionState.done;
        final WebViewController controller = snapshot.data;
        return FloatingActionButton.extended(
              onPressed: !webViewReady
                  ? null
                  : () => navigate(context, controller, goBack: true),
              icon: Icon(Icons.arrow_back),
              backgroundColor: Colors.black,
              label: Text("Voltar"),
        );
      },
    );
  }

  navigate(BuildContext context, WebViewController controller,
      {bool goBack: false}) async {
    bool canNavigate =
        goBack ? await controller.canGoBack() : await controller.canGoForward();
    if (canNavigate) {
      goBack ? controller.goBack() : controller.goForward();
    } else {
      Scaffold.of(context).showSnackBar(
        SnackBar(
            content: Text("Sem histórico anterior")),
      );
    }
  }
}

这基本上就是整个代码。当您真正需要时，Flutter 很酷且易于使用。 谢谢大家！