android - 按下设备后退按钮时出现 Flutter WebView 异常
问题描述
我对 Flutter 很陌生,所以如果这是一个基本问题,请原谅我。
我正在尝试创建一个仅显示全屏 web 视图的 Flutter 应用程序,但我需要设备后退按钮才能返回历史记录。我轻松完成的第一个任务,但第二个任务是斗争。
我按照这个答案中的说明进行操作,但我无法删除一个 360 多行答案的所有杂乱无章的后退按钮并使其工作。
我的代码非常简单:
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:webview_flutter/webview_flutter.dart';
void main() => runApp(MyApp());
WebViewController _controller;
Future<void> _onWillPop(BuildContext context) async {
if (await _controller.canGoBack()) {
_controller.goBack();
} else {
exit(0);
return Future.value(false);
}
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
SystemChrome.setEnabledSystemUIOverlays([]);
return WillPopScope(
onWillPop: () => _onWillPop(context),
child: MaterialApp(title: 'Test App', home: WebView(
initialUrl: 'https://google.com',
javascriptMode: JavascriptMode.unrestricted,
onWebViewCreated: (WebViewController c) => _controller = c,
)),
);
}
}
但是当我尝试按下设备后退按钮时,它会引发以下错误:
java.lang.RuntimeException: Cannot execute operation because FlutterJNI is not attached to native.
at io.flutter.embedding.engine.FlutterJNI.ensureAttachedToNative(FlutterJNI.java:227)
at io.flutter.embedding.engine.FlutterJNI.markTextureFrameAvailable(FlutterJNI.java:554)
at io.flutter.embedding.engine.renderer.FlutterRenderer.markTextureFrameAvailable(FlutterRenderer.java:274)
at io.flutter.embedding.engine.renderer.FlutterRenderer.access$300(FlutterRenderer.java:38)
at io.flutter.embedding.engine.renderer.FlutterRenderer$SurfaceTextureRegistryEntry$1.onFrameAvailable(FlutterRenderer.java:145)
at android.graphics.SurfaceTexture$1.handleMessage(SurfaceTexture.java:211)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:224)
at android.app.ActivityThread.main(ActivityThread.java:7520)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)
Flutter 的 github 上至少有 3 个线程,但没有一个解决方案对我有用。我在这里想念什么?
解决方案
您可以在下面复制粘贴运行完整代码
您可以使用Completer
代码片段
WebViewController controller;
final Completer<WebViewController> _controllerCompleter =
Completer<WebViewController>();
...
onWebViewCreated: (WebViewController c) {
_controllerCompleter.future.then((value) => controller = value);
_controllerCompleter.complete(c);
},
工作演示
完整代码
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:webview_flutter/webview_flutter.dart';
import 'dart:async';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
WebViewController controller;
final Completer<WebViewController> _controllerCompleter =
Completer<WebViewController>();
Future<void> _onWillPop(BuildContext context) async {
print("onwillpop");
if (await controller.canGoBack()) {
controller.goBack();
} else {
exit(0);
return Future.value(false);
}
}
@override
Widget build(BuildContext context) {
return WillPopScope(
onWillPop: () => _onWillPop(context),
child: Scaffold(
body: WebView(
initialUrl: 'https://flutter.dev/',
javascriptMode: JavascriptMode.unrestricted,
onWebViewCreated: (WebViewController c) {
_controllerCompleter.future.then((value) => controller = value);
_controllerCompleter.complete(c);
},
),
),
);
}
}
推荐阅读
- jestjs - 在 Jest/Enzyme 单元测试中最近更新后无法访问以前的 DOM 元素
- maven - 为什么在 maven jetty 插件中设置环境变量不起作用?
- c# - 具有实体框架核心的组集中的前一行
- ios - iOS WKWebView 处理输入文件图片
- apache-spark - 优化collect()的使用
- apache - HBase 批量获取记录
- .net - .NET Core 2.1 无法引用 .NET Framework 4.7.2 类库
- sql - ROW_NUMBER() 仅适用于前 N 条记录
- php - 从网络服务 nusoap 接收 pdf 内容的奇怪行为
- c# - 获取 asp.net 样板存储库使用的 DbContext 实例