Android retrofit

目录

一.简介

二.基本使用

三.注解

四.转换器

五.适配器

六.文件上传与下载

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一.简介

A type-safe HTTP client for Android and Java。封装了OkHttp，也是由Square公司贡献的一个处理网络请求的开源项目。

square/retrofit: A type-safe HTTP client for Android and the JVM (github.com)

在bulid.gradle中添加依赖

implementation 'com.squareup.retrofit2:retrofit:2.11.0'

二.基本使用

服务器域名: https:/ /www.httpbin.org/

接口:post
参数:username，password
接口:get 
参数:usernamespassword

1.根据Http接口创建Java接口

public interface HttpbinService {@POST("post")@FormUrlEncodedCall<ResponseBody> post(@Field("username") String userName,@Field("password") String pwd);@GET("get")Call<ResponseBody> get(@Query("username") String userName,@Query("password") String pwd);
}

2.创建Retrofit对象，并生成接口实现类对象

Retrofit retrofit = new Retrofit.Builder().baseUrl("https://httpbin.org/").build();
HttpbinService httpbinService = retrofit.create(HttpbinService.class);

3.接口实现类对象调用对应方法获得响应

retrofit2.Call<ResponseBody> call = httpbinService.post("xx", "123");call.enqueue(new retrofit2.Callback<ResponseBody>() {@Overridepublic void onResponse(retrofit2.Call<ResponseBody> call, retrofit2.Response<ResponseBody> response) {try {Log.i("TAG",response.body().string());} catch (IOException e) {e.printStackTrace();}}@Overridepublic void onFailure(retrofit2.Call<ResponseBody> call, Throwable throwable) {}});

三.注解

• 方法注解：@GET，@POST，@PUT，@DELETE，@PATH，@HEAD，@OPTIONS，@HTTP

• 标记注解：@FormUrlEncoded，@Multipart，@Streaming

• 参数注解：@Query，@QueryMap，@Body，@Field，@FieldMap，@Part，@PartMap

• 其他注解：@Path，@Header， @Headers，@Url

详细使用请参考 GET (retrofit API) (square.github.io)

public interface HttpbinService {@POST("post")@FormUrlEncodedCall<ResponseBody> post(@Field("username") String userName,@Field("password") String pwd);@GET("get")Call<ResponseBody> get(@Query("username") String userName,@Query("password") String pwd);@HTTP(method = "POST",path = "post",hasBody = true)Call<ResponseBody> http(@Field("username") String userName,@Field("password") String pwd);@POST("post")Call<ResponseBody> postBody(@Body RequestBody body);@POST("{id}") //("/xxx/{pageNum}")@FormUrlEncodedCall<ResponseBody> postInPath(@Path("id") String path,@Header("os") String os1,@Field("username") String userName,@Field("password") String pwd);//@Path("pageNum")@Headers({"os:android","version:1.0"})@POST("post")Call<ResponseBody> postWithHeader();@POST()Call<ResponseBody> postUrl(@Url String url);
}

四.转换器

在我们接到服务器的响应后，目前无论是OkHttp还是Retrofit都只能接收到String字符串类型的数据，在实际开发中，经常需要对字符串进行解析将其转变为一个Java Bean对象。比如服务器响应数据为JSON格式字符串，那么可以自己利用GSON库完成反序列化的操作。而Retrofit提供了多个转换器使得响应能够完成自动的数据转换。以json解析为例：

添加依赖

implementation 'com.squareup.retrofit2:converter-gson:2.11.0'

手动转换

public interface WanAndroidService {@POST("user/login")@FormUrlEncodedCall<ResponseBody> login(@Field("username") String username,@Field("password") String pwd);
}

Retrofit retrofit = new Retrofit.Builder().baseUrl("https://www.wanandroid.com/").build();WanAndroidService wanAndroidService = retrofit.create(WanAndroidService.class);@Testpublic void loginTest() throws IOException {Call<ResponseBody> call = wanAndroidService.login("xxx","123456");Response<ResponseBody> response  =call.execute();String result  = response.body().string();System.out.println(result);//手动进行数据转换BaseResponse baseResponse  = new Gson().fromJson(result,BaseResponse.class);System.out.println(baseResponse);}

自动转换

修改接口方法：

@POST("post")

@FormUrlEncoded

Call<JavaBean> post(@Field("username") String userName, @Field("password") String pwd);

public interface WanAndroidService2 {@POST("user/login")@FormUrlEncodedCall<BaseResponse> login(@Field("username") String username, @Field("password") String pwd);
}

Retrofit retrofit1 = new Retrofit.Builder().baseUrl("https://www.wanandroid.com/").addConverterFactory(GsonConverterFactory.create())  //添加转换器.build();WanAndroidService2 wanAndroidService2 = retrofit1.create(WanAndroidService2.class);@Testpublic void loginConvertTest() throws IOException {Call<BaseResponse> call = wanAndroidService2.login("xxx","123456");Response<BaseResponse> response = call.execute();BaseResponse baseResponse = response.body();System.out.println(baseResponse);}

五.适配器

在实际开发中，可能会存在：需要先请求A接口，再请求B接口的情况。比如需要请求获取收藏文章列表，但是需要先登录拿到Cookie才能请求收藏文章列表接口。此时请求就有了先后顺序，为了完成这个功能，需要不断回调。Retrofit的接口方法返回类型必须是Call，如果能够将Call改为RxJava中的Observable，对于嵌套的情况，就能得到非常方便优雅的解决。这就是适配器的功能，如果我们想要返回的不是Call，适配器就能够帮助我们转换为其他类型。以RxJava3为例：

添加依赖

implementation 'com.squareup.retrofit2:adapter-rxjava3:2.11.0'
implementation 'io.reactivex.rxjava3:rxandroid:3.0.2'

修改接口方法：

@POST("post")

@FormUrlEncoded

Observable<JavaBean> post(@Field("username") String userName, @Field("password") String pwd);

@POST("user/login")@FormUrlEncodedFlowable<BaseResponse> login2(@Field("username") String username, @Field("password") String pwd);@GET("lg/collect/list/{pageNum}/json")Flowable<ResponseBody> getArticle(@Path("pageNum") int pageNum);

Map<String, List<Cookie>> cookies = new HashMap<>();Retrofit retrofit2 = new Retrofit.Builder().baseUrl("https://www.wanandroid.com/").callFactory(new OkHttpClient.Builder().cookieJar(new CookieJar() {@Overridepublic void saveFromResponse(HttpUrl httpUrl, List<Cookie> list) {cookies.put(httpUrl.host(), list);}@Overridepublic List<Cookie> loadForRequest(HttpUrl url) {List<Cookie> cookies = WanAndroidUnitTest.this.cookies.get(url.host());return cookies == null ? new ArrayList<>() : cookies;}}).build()).addConverterFactory(GsonConverterFactory.create())  //添加转换器.addCallAdapterFactory(RxJava3CallAdapterFactory.create())  //添加适配器.build();WanAndroidService2 wanAndroidService3 = retrofit2.create(WanAndroidService2.class);@Testpublic void rxjavaTest() {wanAndroidService3.login2("xxxx","123456").flatMap(new Function<BaseResponse, Publisher<ResponseBody>>() {@Overridepublic Publisher<ResponseBody> apply(BaseResponse baseResponse) throws Throwable {return wanAndroidService3.getArticle(0);}}).observeOn(Schedulers.io()).subscribeOn(Schedulers.newThread())   //AndroidSchedulers.mainThread().subscribe(new Consumer<ResponseBody>() {@Overridepublic void accept(ResponseBody responseBody) throws Throwable {System.out.println(responseBody.string());}});while (true){}}

六.文件上传与下载

@POST("post")@MultipartCall<ResponseBody> upload(@Part MultipartBody.Part file);@GETCall<ResponseBody> download(@Url String url);

@Testpublic void uploadFileTest() throws IOException {File file = new File("H:\\Users\\ASUS\\Desktop\\f1.txt");MultipartBody.Part part = MultipartBody.Part.createFormData("file1", "f1.txt",RequestBody.create(MediaType.parse("text/plain"), file));Call<ResponseBody> call = uploadService.upload(part);System.out.println(call.execute().body().string());}@Testpublic void downloadFileTest() throws IOException {Response<ResponseBody> response = uploadService.download("https://xxx.apk").execute();InputStream inputStream = response.body().byteStream();FileOutputStream fos = new FileOutputStream("H:\\Users\\ASUS\\Desktop\\1.apk");int len;byte[] buffer = new byte[4096];while ((len = inputStream.read(buffer)) != -1){fos.write(buffer,0,len);}fos.close();inputStream.close();}

相关参考

Retrofit (square.github.io)​​​​​​​

ReactiveX/RxJava: RxJava – Reactive Extensions for the JVM – a library for composing asynchronous and event-based programs using observable sequences for the Java VM. (github.com)

ReactiveX/RxAndroid: RxJava bindings for Android (github.com)​​​​​​​