背景
首先看到，相信大家已经血压飙升了，既然都用了Flutter，怎么还用原生的网络库呢？这不是多此一举么。emmmmm，当我看到这个需求的时候一样恼火。但因为我们项目中使用的Dio库不支持查询DNS、SSL等所需时间（至少我没找到），而Okhttp却可以。因此，不得以只能借助原生网络库去实现此功能。
实现方案
既然必须要去实现，那摆在面前的问题就是如何去实现了。最简单粗暴的一个方式，就是通过建立一个Flutter Channel将网络请求的所有信息传到原生，但脑补一波后，发现实现起来太过麻烦，一堆header,body,data等信息都需要自己组装，并且致命的是需要改动现有项目的请求方式。因此为了避免项目大改，最后看中了Dio提供的interceptors（拦截器）功能，在拦截器中，我们可以对网络请求进行拦截，拦截后再通过FlutterChannel发给原生进行网络请求。这样既避免了项目改动，也省去了数据组装，很容易的达到了目标。
实现步骤
- 首先定义一个拦截器（NativeNetInterceptor），用来转发网络请求，在onRequest中，我们调用了NativeNet.sendRequestToNative方法，用来接收接口中的参数（url、header、body、data、等等等），方便下一步转发。catch模块主要用来捕获异常，如果是DioError，直接
reject，如果是其他异常，可以调用handler.next(options)继续走Dio请求，当作兜底方案。这里我注释掉了。
class NativeNetInterceptor extends Interceptor {
final Dio dio;
final NativeNetOptions options;
NativeNetInterceptor({
required this.dio,
NativeNetOptions? options,
}) : options = options ?? NativeNetOptions();
@override
void onRequest(
RequestOptions options, RequestInterceptorHandler handler) async {
try {
Response response = await NativeNet.sendRequestToNative(options);
return handler.resolve(response, true);
} catch (e) {
if (e.runtimeType == DioError) {
return handler.reject(e as DioError);
} else {
// TODO:如果担心原生有问题，可打开下方注释。
// handler.next(options);
rethrow;
}
}
}
}- NativeNet的实现,这里主要是将Dio
options中所带的信息发送给原生，并将原生返回信息进行组装。
class NativeNet {
static const MethodChannel _channel = MethodChannel('nativeNet');
static Future<Response> sendRequestToNative(RequestOptions options) async {
final String url = options.baseUrl + options.path;
Map channelParams = _getChannelParams(
url,
options.method,
queryParameters: options.queryParameters,
data: options.data,
header: options.headers,
timeoutInterval: options.connectTimeout,
);
return await _sendRequestToNative(options, channelParams);
}
static Future<Response> _sendRequestToNative(
RequestOptions options, Map params) async {
final Map nativeResponse =
await _channel.invokeMapMethod('net', params) ?? {};
final Response response = Response(requestOptions: options);
if (nativeResponse.containsKey('headers')) {
final Map nativeResponseHaders = nativeResponse['headers'];
nativeResponseHaders.forEach((key, value) {
response.headers.set(key, value);
});
}
response.statusCode = nativeResponse['statusCode'] ?? -1;
response.statusMessage = nativeResponse['statusMessage'] ?? '无message';
if (Platform.isAndroid) {
if (nativeResponse.containsKey('data')) {
String jsonData = nativeResponse['data'];
try {
Map<String, dynamic> data = convert.jsonDecode(jsonData);
response.data = data;
} on FormatException catch (e) {
///转换异常后手动构造一下
debugPrint("Http FormatException");
Map map = {};
map["data"] = jsonData;
response.data = map;
}
} else {
response.data = {};
}
} else {
Map<String, dynamic> data =
Map<String, dynamic>.from(nativeResponse['data'] ?? {});
response.data = data;
}
if (nativeResponse.containsKey('error')) {
//网络请求失败
Map? errorData = nativeResponse['error'];
throw DioError(
requestOptions: options, response: response, error: errorData);
}
return response;
}
static Map<String, dynamic> _getChannelParams(
String url,
String method, {
Map<String, dynamic>? queryParameters,
Map<String, dynamic>? data,
Map<String, dynamic>? header,
num? timeoutInterval,
num? retryCount,
}) {
Map<String, dynamic> channelParams = {
'url': url,
'method': method,
};
if (queryParameters != null) {
channelParams['queryParameters'] = queryParameters;
}
if (data != null) {
channelParams['data'] = data;
}
if (header != null) {
channelParams['header'] = header;
}
if (retryCount != null) {
channelParams['retryCount'] = retryCount;
}
if (timeoutInterval != null) {
channelParams['timeoutInterval'] = timeoutInterval;
}
return channelParams;
}
}- 原生实现，这里贴出安卓代码，请求完之后，无论成功失败，都调用result.success将处理好的数据返回给flutter。具体的
ANDROID/IOS网络请求这里就略过了，相信大家都用的很成熟了。
class NativeNetPlugin : FlutterPlugin, MethodCallHandler {
/// The MethodChannel that will the communication between Flutter and native Android
///
/// This local reference serves to register the plugin with the Flutter Engine and unregister it
/// when the Flutter Engine is detached from the Activity
private lateinit var channel: MethodChannel
private var gson: Gson = Gson()
private val mTag = "Android NativeNetPlugin"
override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
channel = MethodChannel(flutterPluginBinding.binaryMessenger, "nativeNet")
channel.setMethodCallHandler(this)
}
override fun onMethodCall(@NonNull call: MethodCall, @NonNull result: Result) {
if (call.method == "net") {
val channelParams = call.arguments as Map<String, Any>
var method = ""
if (channelParams.containsKey("method")) {
method = channelParams["method"] as String
}
var url = ""
if (channelParams.containsKey("url")) {
url = channelParams["url"] as String
}
var header = HashMap<String, String>()
if (channelParams.containsKey("header")) {
header = channelParams["header"] as HashMap<String, String>
}
val headers = HttpHeaders()
headers.headersMap = getMapValueForLinkedHashMap(header)
// params
var queryParameters = HashMap<String, String>()
if (channelParams.containsKey("queryParameters")) {
queryParameters = channelParams["queryParameters"] as HashMap<String, String>
}
//post body
var data = HashMap<String, Any>()
if (channelParams.containsKey("data")) {
data = channelParams["data"] as HashMap<String, Any>
}
//超时时间
var timeoutInterval: Int = 1000 * 15
if (channelParams.containsKey("timeoutInterval")) {
timeoutInterval = channelParams["timeoutInterval"] as Int
}
val mTimeOut =
Timeout(timeoutInterval, timeoutInterval, timeoutInterval, TimeUnit.MILLISECONDS)
//重试次数
var retryCount = 0
if (channelParams.containsKey("retryCount")) {
retryCount = channelParams["retryCount"] as Int
}
when (method) {
"POST" -> {
...
//请求成功/失败后调用此方法，
result.success(dealResponse(response))
}
"GET" -> {
...
}
"DELETE" -> {
...
}
"PUT" -> {
...
}
"HEAD" -> {
...
}
else -> {
result.notImplemented()
}
}
} else {
result.notImplemented()
}
}
private fun dealResponse(
response: Response<String>
): Map<String, Any?> {
val map = HashMap<String, Any?>()
if (BuildConfig.DEBUG) {
Log.e(mTag, "dealResponse isSuccessful: ${response.code()}")
Log.e(mTag, "dealResponse code: ${response.code()}")
Log.e(mTag, "dealResponse message: ${response.message()}")
Log.e(mTag, "dealResponse body: ${response.body()}")
Log.e(mTag, "dealResponse headers: ${response.headers()}")
}
map["statusCode"] = response.code()
response.message()?.let {
map["statusMessage"] = it
} ?: let {
map["statusMessage"] = ""
}
response.body()?.let {
map["data"] = it
} ?: let {
map["data"] = ""
}
response.headers()?.let {
map["headers"] = it.toMap()
} ?: let {
map["headers"] = HashMap<String, Any>()
}
if (response.code() != 200) {
//失败
val errorMap = HashMap<String, Any?>()
response.exception?.let {
errorMap["code"] = response.code()
errorMap["domain"] = it.toString()
errorMap["description"] = it.message
} ?: let {
errorMap["code"] = response.code()
errorMap["domain"] = map["statusMessage"]
errorMap["description"] = "HttpException"
}
map["error"] = errorMap
}
return map
}
//map 转 LinkedHashMap
private fun getMapValueForLinkedHashMap(dataMap: Map<String, String>): LinkedHashMap<String, String> {
val returnMap: LinkedHashMap<String, String> = LinkedHashMap()
if (dataMap.isNullOrEmpty()) {
return returnMap
}
val iterator = dataMap.keys.iterator()
while (iterator.hasNext()) {
val objKey = iterator.next()
val objValue = dataMap[objKey]
returnMap[objKey] = objValue.toString()
}
return returnMap
}
override fun onDetachedFromEngine(@NonNull binding: FlutterPlugin.FlutterPluginBinding) {
channel.setMethodCallHandler(null)
}
}4.最后调用dio.interceptors.add(NativeNetInterceptor(dio: dio));将我们写好的NativeNetInterceptor加入Dio拦截器。
交互协议
Request（Flutter To Native）
{
"url": "https://www.baidu.com", // 必传 请求地址
"method": "GET", //必传 请求方式 GET POST HEAD PUT DELETE
"queryParameters":{}, //可选 query参数
"data":{}, //可选 body参数
"header":{}, //可选 请求头
"timeoutInterval":15000, //可选 （毫秒） 链接超时时常
"retryCount": 0 //可选 重试次数，默认0
}Response（Native To Flutter）
// native返回 成功
{
"data":{}, //接口原始返回内容
"headers":{}, //返回头
"statusCode":200, //http状态码
"statusMessage":"请求成功" //http状态码对应文案
}
// native返回 失败
{
"data":{}, //接口原始返回内容
"headers":{}, //返回头
"statusCode":404, //http状态码
"statusMessage":"找不到对象", //http状态码对应文案
"error":{
"code":-3001, //错误码
"domain":"URLDmain", // 错误大分类
"description":"错误详情" // 错误详情
}
}注意点
添加NativeNetInterceptor,如果有多个拦截器，例如LogInterceptors等等，需要将NativeNetInterceptor放到最后。
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