Flutter WebView 预加载实现方法(Http Server)

dependencies:
  flutter:
    sdk: flutter
  http: ^0.13.4

abstract class HttpServer implements Stream<HttpRequest>

var server = await HttpServer.bind(InternetAddress.loopbackIPv4, 0);

curAddresses = _server!.address.address;
curPort = _server!.port;
_server!.sessionTimeout = 60;

serverSub = _server!.listen(_responseWebViewReq, onError: (e) => log(e, name: _logKey));

_responseWebViewReq(HttpRequest request)

var uri = request.requestedUri;
final data = await _getResponseData(uri);
request.response.add(data);

request.response.headers.add('Content-Type', '$mime; charset=utf-8');

request.response.close();

{
    "option": [
        {
            "key": "test",
            "open": 1,
            "priority": 0,
            "version": "20222022"
        },
        {
            "key": "test2",
            "open": 0,
            "priority": 0,
            "version": "20222222"
        }
    ],
    "assets": {
        "test": {
            "compress": "/local-server/test.zip"
        },
        "test2": {
            "compress": "/local-server/test2.zip"
        }
    },
    "basics": {
        "common": {
            "compress": "/local-server/common.zip",
            "version": "20220501"
        }
    },
    "local_server_open": 1
}

// 触发basics预下载
LocalServerDownloadService.instance.preloadBasicsData(json['basics'], basics, oldBasic);

// 触发assets预下载
LocalServerDownloadService.instance.preloadAssetsData(_diffAssets(value, assets));

Dio().download(queueItem.zipUrl, zipPath).then((resp) {
  if (resp.statusCode != 200) {
    _log('下载ls 压缩包失败  err:${resp.statusCode} zipUrl:${queueItem.zipUrl}');
    throw Exception('下载ls 压缩包失败  err:${resp.statusCode}');
  }
  return unarcHive(queueItem, zipPath);
})

// 找到对应zipUrl的本地文件路径
Directory saveDirct = LocalServerConfiguration.getCurrentZipPathSyncDirectory(item.zipUrl);
final zipFile = File(downPath);
if (!zipFile.existsSync()) {
  throw Exception('Local server 下载包文件路径不存在：$downPath');
}
List<int> bytes = zipFile.readAsBytesSync();
Archive archive = ZipDecoder().decodeBytes(bytes);
···
// 清理之前的缓存
File oldfile = File(downPath);
if (oldfile.existsSync()) {
  oldfile.deleteSync();
}

queueItem.loadState = LoadStateType.failure;
queueItem.downloadCount += 1;

// 处理 assets 资源，和版本控制
LocalServerConfiGCache.getOptions().then((oldOptions) {
  // assets 缓存和版本处理
  LocalServerConfigCache.getAssets().then((value) {
    var oldAssets = value;
    // 版本不对，则移除，并需要下载
    if (oldOptions != null) {
      for (var e in oldOptions) {
        var res = options.where((element) => element.key == e.key);
        if (res.isNotEmpty && res.first.version != e.version) {
          _log('资源 ${e.key} 需要更新');
          oldAssets?.removeWhere((key, value) => key == e.key);
        }
      }
    }
    // 触发预下载
    LocalServerDownloadService.instance.preloadAssetsData(_diffAssets(value, assets));
  **});**
});

_assetsBucket.forEach((key, value) {
  for (var tmpItem in value) {
    switch(tmpItem.loadState) {
      case LoadStateType.unLoad:
      case LoadStateType.loading:
        _addQueue(tmpItem);
        break;
      case LoadStateType.success:
        sucCount++;
        break;
      case LoadStateType.failure:
        _addQueue(tmpItem);
        break;
    }
  }
});

return LocalServerService.instance.getLocalServerWebUrl(h5Path, query.isEmpty ? path : path + '?' + query);

String _getLocalServerWebUrl(String oriUrl, String localServerKey) {
  return 'http://${curAddresses ?? InternetAddress.loopbackIPv4.address}:$curPort$localServerKey';
}

@override
void initState() {
  super.initState();
  log('页面开始加载：${DateTime.now()}', name: 'web-time');
  _localServerBuilder = LocalServerCacheBinder()..initBinder();
  LocalServerWebViewManager.instance.reGISterBuilder(_localServerBuilder);
  _innerUrl = _localServerBuilder.convertH5Url2LocalServerUrl(widget.url);
}

WebView(
  initialUrl: _innerUrl,
  debuggingEnabled: true,
  ···
）

// 找不到本地文件，使用网络下载拿到原始数据
var nowUri = request.requestedUri;
var baseDomain = LocalServerCacheBinderSetting.instance.baseDomain;
var baseUri = Uri.parse(baseDomain);
// 替换为原始url
nowUri = nowUri.replace(
    scheme: baseUri.scheme, host: baseUri.host, port: baseUri.port);
// dio请求，responseType 必须是bytes
var res = await Dio().getUri(nowUri, options: Options(responseType: ResponseType.bytes));
data = res.data;
name = basename(nowUri.path.split('/').toList().last);
mime = lookupMimeType(name);

request.response.headers.add('Content-Type', '$mime; charset=utf-8');
return data;

class LocalServerClientManager implements LocalServerStatusHandler,
    LocalServerDownloadServiceProtocol

class LocalServerWebViewManager extends LocalServerClientManager {
  factory LocalServerWebViewManager() => _getInstance();
  static LocalServerWebViewManager get instance => _getInstance();
  static LocalServerWebViewManager? _instance;
  static LocalServerWebViewManager _getInstance() {
    _instance ??= LocalServerWebViewManager._internal();
    return _instance!;
  }
  LocalServerWebViewManager._internal();
  /// 测试的配置
  void initSetting() {
    init();
    LocalServerCacheBinderSetting.instance.setBaseHost('https://jomin-web.web.app');
    Map<String, dynamic> baCache = {'common': {'compress': '/local-server/common.zip', "version": "20220503"}};
    LocalServerClientConfig localServerClientConfig = LocalServerClientConfig.fromJson({
      'option': [{'key': 'test-one', 'open': 1, 'priority': 0, "version": "20220503"}],
      'assets': {
        'test-one': {'compress': '/local-server/test-one.zip'}
      },
      'basics': baCache,
    });
    prepareManager(localServerClientConfig);
    startLocalServer();
  }
}