flutter中WebView的使用及JavaScript桥接的问题记录

一、在原生安卓中的使用

在原生安卓中一般采用的是@JavascriptInterface注解和WebView的addJavascriptInterface方法实现桥接

实现一个@JavascriptInterface的注解。

class JavaScriptCall() {

复制代码

 @JavascriptInterface
 fun CallApp(string: String) {
     //{"action":"geolocationGet","jsCallBackId":"func1703575966310","params":{"coordinate":1,"withReGeocode":false}}
     LogUtils.e("CallApp" + string)
 }

}

继承WebView使用addJavascriptInterface添加桥接方法。

class BridgeWebView : WebView{
var bridgeJs = JavaScriptCall(this)

复制代码

 constructor(context: Context) : super(context) {
     init()
 }

 constructor(context: Context, attrs: AttributeSet?) : super(context, attrs) {
     init()
 }

 constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : super(context, attrs, defStyleAttr) {
     init()
 }

 constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int) : super(context, attrs, defStyleAttr, defStyleRes) {
     init()
 }

 private fun init() {
     addJavascriptInterface(bridgeJs, "ISANDNative")
 }

}

js端调用桥接方法。

// JavaScript代码调用Android原生
ISANDNative.CallApp('{"action":"closeWebView","jsCallBackId":"...","params":{...}}');

二、在flutter端的使用

在pubspec.yaml中引用webview的包。

webview_flutter: ^4.0.7
创建一个widget实现WebViewController和WebViewWidget(老版的WebView已不建议使用)。

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

class UserAgreementWebPage extends StatefulWidget {
final String url;
final String title;

const UserAgreementWebPage({Key? key, required this.url, this.title = ''}) : super(key: key);

@override
State createState() => _UserAgreementWebPageState();
}

class _UserAgreementWebPageState extends State {
late final WebViewController _controller;
bool _isLoading = true;

@override
void initState() {
super.initState();
复制代码
```
 // 初始化WebViewController
 _controller = WebViewController()
   ..setJavaScriptMode(JavaScriptMode.unrestricted)
   ..addJavaScriptChannel(
     'ISANDNative',
     onMessageReceived: (JavaScriptMessage message) {
       print('接收到JS消息: ${message.message}');
       Get.back();
     },
   )
 // 添加额外的错误处理通道，便于调试
   ..addJavaScriptChannel(
     'debugChannel',
     onMessageReceived: (JavaScriptMessage message) {
       print('调试信息: ${message.message}');
     },
   )
   ..setNavigationDelegate(
     NavigationDelegate(
       onPageStarted: (String url) {
         setState(() {
           _isLoading = true;
         });
       },
       onPageFinished: (String url) {
         setState(() {
           _isLoading = false;
         });
       },
       onWebResourceError: (WebResourceError error) {
         setState(() {
           _isLoading = false;
         });
         // 处理错误
         print('Web错误: ${error.description}');
       },
       onNavigationRequest: (NavigationRequest request) async {
         print("onNavigationRequest:${request.url}");
         return NavigationDecision.navigate;
       },
     ),
   )
   ..loadRequest(Uri.parse(widget.url));
```
}

@override
Widget build(BuildContext context) {
return AnnotatedRegion(
value: SystemUiOverlayStyle(
statusBarColor: Colors.white, // 设置状态栏背景色
),
child: SafeArea(
child: Stack(
children: [
WebViewWidget(controller: _controller),
if (_isLoading)
const Center(
child: CircularProgressIndicator(),
),
],
),
),
);
}

@override
void dispose() {
// 恢复状态栏的默认样式
SystemChrome.setSystemUIOverlayStyle(const SystemUiOverlayStyle(
statusBarColor: Colors.transparent, // 根据您应用的默认样式设置
statusBarIconBrightness: Brightness.dark, // 根据您应用的默认样式设置
));
super.dispose();
}
}

其中的addJavaScriptChannel即是添加桥接的方法，ISANDNative为通道名称，onMessageReceived中为收到的消息。

通过上述配置后会发现实际还是收不到通道的消息，这是因为原生安卓和flutter调用的差异导致的。

Android原生调用方式：

复制代码

// JavaScript代码调用Android原生
ISANDNative.CallApp('{"action":"closeWebView","jsCallBackId":"...","params":{...}}');

Flutter调用方式：

复制代码

// JavaScript代码调用Flutter
ISANDNative.postMessage('{"action":"closeWebView","jsCallBackId":"...","params":{...}}');

如果Web端采用了flutter的带哦用方式，我们就可以正常收到通道的消息了。

如果您无法修改Web页面的JavaScript代码，可以在Flutter中注入一个适配脚本，将CallApp调用转换为postMessage。完整代码如下：

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

class UserAgreementWebPage extends StatefulWidget {
final String url;
final String title;

const UserAgreementWebPage({Key? key, required this.url, this.title = ''}) : super(key: key);

@override
State createState() => _UserAgreementWebPageState();
}

class _UserAgreementWebPageState extends State {
late final WebViewController _controller;
bool _isLoading = true;

@override
void initState() {
super.initState();

复制代码

 // 初始化WebViewController
 _controller = WebViewController()
   ..setJavaScriptMode(JavaScriptMode.unrestricted)
   ..addJavaScriptChannel(
     'ISANDNative',
     onMessageReceived: (JavaScriptMessage message) {
       print('接收到JS消息: ${message.message}');
       Get.back();
     },
   )
 // 添加额外的错误处理通道，便于调试
   ..addJavaScriptChannel(
     'debugChannel',
     onMessageReceived: (JavaScriptMessage message) {
       print('调试信息: ${message.message}');
     },
   )
   ..setNavigationDelegate(
     NavigationDelegate(
       onPageStarted: (String url) {
         setState(() {
           _isLoading = true;
         });
       },
       onPageFinished: (String url) {
         // 注入适配脚本，将CallApp调用转换为postMessage
         _controller.runJavaScript('''
         // 创建一个包装器来捕获CallApp调用
         window.ISANDNative_Original = window.ISANDNative;
         window.ISANDNative = {
           CallApp: function(jsonString) {
             // 转换为Flutter的调用方式
             window.ISANDNative_Original.postMessage(jsonString);
           }
         };
       ''');

         setState(() {
           _isLoading = false;
         });
       },
       onWebResourceError: (WebResourceError error) {
         setState(() {
           _isLoading = false;
         });
         // 处理错误
         print('Web错误: ${error.description}');
       },
       onNavigationRequest: (NavigationRequest request) async {
         print("onNavigationRequest:${request.url}");
         return NavigationDecision.navigate;
       },
     ),
   )
   ..loadRequest(Uri.parse(widget.url));

}

@override
Widget build(BuildContext context) {
return AnnotatedRegion(
value: SystemUiOverlayStyle(
statusBarColor: Colors.white, // 设置状态栏背景色
),
child: SafeArea(
child: Stack(
children: [
WebViewWidget(controller: _controller),
if (_isLoading)
const Center(
child: CircularProgressIndicator(),
),
],
),
),
);
}

@override
void dispose() {
// 恢复状态栏的默认样式
SystemChrome.setSystemUIOverlayStyle(const SystemUiOverlayStyle(
statusBarColor: Colors.transparent, // 根据您应用的默认样式设置
statusBarIconBrightness: Brightness.dark, // 根据您应用的默认样式设置
));
super.dispose();
}
}

经过上述操作后，就可以在日志打印中看到我们收到的消息了。