Android使用Retrofit进行网络请求

Retrofit 简介

用于Android和Java平台的一款类型安全的HTTP客户端，通过一个Java接口实现HTTP请求对象，如下：

public interface Github {
    @GET("/repos/{owner}/{repo}/contributors")
    Call> contributors(
            @Path("owner") String owner,
            @Path("repo") String repo);
}

Android 平台使用示例

步骤如下：

• 添加 Retrofit 相关依赖库

//retrofit2 依赖库
implementation 'com.squareup.retrofit2:retrofit:2.4.0'
//Gson 数据解析器依赖库
implementation 'com.squareup.retrofit2:converter-gson:2.4.0'
//okhttp3 输出网络请求日志依赖库
implementation 'com.squareup.okhttp3:logging-interceptor:3.4.1'

• 创建接收服务器返回数据对应的实体类

//创建接收服务器返回数据的类
public class Contributor {

    public final String login;
    public final int contributions;

    public Contributor(String login, int contributions) {
        this.login = login;
        this.contributions = contributions;
    }
}

• 创建用于描述网络请求的接口

//创建用于网络请求的接口
public interface Github {
    @GET("/repos/{owner}/{repo}/contributors")
    Call> contributors(
            @Path("owner") String owner,
            @Path("repo") String repo);
}

• *配置打印网络请求日志

HttpLoggingInterceptor loggingInterceptor;
//打印网络请求相关日志
loggingInterceptor = new HttpLoggingInterceptor(new HttpLoggingInterceptor.Logger() {
      @Override
      public void log(String message) {
           //打印retrofit日志
           Log.i("retrofitLog: ", message);
      }
});
loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);

//为了打印日志，需要配置OkHttpClient
OkHttpClient client = new OkHttpClient.Builder()
                .addInterceptor(loggingInterceptor)
                .build();

• 创建Retrofit对象

Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(API_GITHUB_URL)
                .client(client)
                .addConverterFactory(GsonConverterFactory.create())
                .build();

• 创建网络请求接口实例

//创建网络接口实例
Github github = retrofit.create(Github.class);

//对发送请求进行封装
Call> call = github.contributors("square", "retrofit");

• 发送网络请求（异步 / 同步）并对返回数据进行处理

//发送同步请求时不能直接在UI线程进行，不然会报错：NetworkOnMainThreadException
//发送请求，获取请求的数据
List contributors = call.execute().body();
StringBuilder result = new StringBuilder();
for (Contributor contributor : contributors) {
      result.append(contributor.login + " (" + contributor.contributions + ")\n");
}
Log.e("result", result.toString());

---

主要代码如下

• MainActivity.java

  public class MainActivity extends AppCompatActivity {
  
  private TextView tv_request_result;
  public static final String API_GITHUB_URL = "https://api.github.com";
  HttpLoggingInterceptor loggingInterceptor;
  
  private Handler handler = new Handler(){
      @Override
      public void handleMessage(Message msg) {
          super.handleMessage(msg);
          Bundle data = msg.getData();
          String result = data.getString("result");
          tv_request_result.setText(result);
      }
  };
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      initView();
  
      //打印网络请求相关日志
      loggingInterceptor = new HttpLoggingInterceptor(new HttpLoggingInterceptor.Logger() {
          @Override
          public void log(String message) {
              //打印retrofit日志
              Log.i("retrofitLog: ", message);
          }
      });
      loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
  
      new Thread(runnable).start(); //不能在UI线程中进行网络请求
  
  }
  
  private void initView() {
      tv_request_result = (TextView) findViewById(R.id.tv_request_result);
  }
  
  //发送网络请求
  private String request() throws IOException {
      //为了打印日志，需要配置okhttp
      OkHttpClient client = new OkHttpClient.Builder()
              .addInterceptor(loggingInterceptor)
              .build();
  
      //创建Retrofit对象
      Retrofit retrofit = new Retrofit.Builder()
              .baseUrl(API_GITHUB_URL)
              .client(client)
              .addConverterFactory(GsonConverterFactory.create())
              .build();
  
      //创建网络接口实例
      Github github = retrofit.create(Github.class);
  
      //对发送请求进行封装
      Call> call = github.contributors("square", "retrofit");
  
      //发送请求，获取请求的数据
      List contributors = call.execute().body();
      StringBuilder result = new StringBuilder();
      for (Contributor contributor : contributors) {
          result.append(contributor.login + " (" + contributor.contributions + ")\n");
      }
      Log.e("result", result.toString());
      return result.toString();
  }
  
  //网络请求线程
  Runnable runnable = new Runnable() {
      @Override
      public void run() {
          try {
              String result = request();
              Message msg = new Message();
              Bundle data = new Bundle();
              data.putString("result", result);
              msg.setData(data);
              handler.sendMessage(msg);
          } catch (IOException e) {
              Log.e("request_erro", e.toString());
          }
      }
  };
  }

• activity_main.xml

  
  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="match_parent">
  
      <ScrollView
          android:layout_width="match_parent"
          android:layout_height="match_parent">
  
          <TextView
              android:id="@+id/tv_request_result"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:textSize="20sp" />
      ScrollView>
  LinearLayout>

• 程序运行结果
  
• 网络请求日志如下：

07-02 16:07:41.145 17443-17462/com.example.xuyue.learnretrofit I/retrofitLog:: --> GET https://api.github.com/repos/square/retrofit/contributors http/1.1
    --> END GET
07-02 16:07:43.275 17443-17462/com.example.xuyue.learnretrofit I/retrofitLog:: <-- 200 OK https://api.github.com/repos/square/retrofit/contributors (2129ms)
    Server: GitHub.com
    Date: Mon, 02 Jul 2018 08:07:45 GMT
    Content-Type: application/json; charset=utf-8
    Transfer-Encoding: chunked
    Status: 200 OK
    X-RateLimit-Limit: 60
    X-RateLimit-Remaining: 30
    X-RateLimit-Reset: 1530522209
    Cache-Control: public, max-age=60, s-maxage=60
07-02 16:07:43.276 17443-17462/com.example.xuyue.learnretrofit I/retrofitLog:: Vary: Accept
    ETag: W/"0313af265d6c3206fe7e38545918e2bf"
    Last-Modified: Mon, 02 Jul 2018 07:42:01 GMT
    X-GitHub-Media-Type: github.v3; format=json
    Link: //api.github.com/repositories/892275/contributors?page=2>; rel="next", ; rel="last"
    Access-Control-Expose-Headers: ETag, Link, Retry-After, X-GitHub-OTP, X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset, X-OAuth-Scopes, X-Accepted-OAuth-Scopes, X-Poll-Interval
    Access-Control-Allow-Origin: *
    Strict-Transport-Security: max-age=31536000; includeSubdomains; preload
    X-Frame-Options: deny
    X-Content-Type-Options: nosniff
    X-XSS-Protection: 1; mode=block
    Referrer-Policy: origin-when-cross-origin, strict-origin-when-cross-origin
    Content-Security-Policy: default-src 'none'
    X-Runtime-rack: 0.075905
    X-GitHub-Request-Id: 90E0:3CD2:61BDD85:BCDE66D:5B39DD50
07-02 16:07:43.288 17443-17462/com.example.xuyue.learnretrofit I/retrofitLog:: [{"login":"JakeWharton","id":66577,"node_id":"MDQ6VXNlcjY2NTc3","avatar_url":"https://avatars0.githubusercontent.com/u/66577?v=4","gravatar_id":"","url":"https://api.github.com/users/JakeWharton","html_url":"https://github.com/JakeWharton","followers_url":"https://api.github.com/users/JakeWharton/followers","following_url":"https://api.github.com/users/JakeWharton/following{/other_user}","gists_url":"https://api.github.com/users/JakeWharton/gists{/gist_id}","starred_url":"https://api.github.com/users/JakeWharton/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/JakeWharton/subscriptions","organizations_url":"https://api.github.com/users/JakeWharton/orgs","repos_url":"https://api.github.com/users/JakeWharton/repos","events_url":"https://api.github.com/users/JakeWharton/events{/privacy}","received_events_url":"https://api.github.com/users/JakeWharton/received_events","type":"User","site_admin":false,"contributions":911},{"login":"swankjesse","id":133019,"node_id":"MDQ6VXNlcjEzMzAxOQ==","avatar_url":"https://avatars3.githubusercontent.com/u/133019?v=4","gravatar_id":"","url":"https://api.github.com/users/swankjesse","html_url":"https://github.com/swankjesse","followers_url":"https://api.github.com/users/swankjesse/followers","following_url":"https://api.github.com/users/swankjesse/following{/other_user}","gists_url":"https://api.github.com/users/swankjesse/gists{/gist_id}","starred_url":"https://api.github.com/users/swankjesse/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/swankjesse/subscriptions","organizations_url":"https://api.github.com/users/swankjesse/orgs","repos_url":"https://api.github.com/users/swankjesse/repos","events_url":"https://api.github.com/users/swankjesse/events{/privacy}","received_events_url":"https://api.github.com/users/swankjesse/received_events","type":"User","site_admin":false,"contributions":224},{"login":"pforhan","id":331925,"node_id":"MDQ6VXNlcjMzMTkyNQ==","avatar_url":"https://avatars3.githubusercontent.com/u/331925?v=4","gravatar_id":"","url":"https://api.github.com/users/pforhan","html_url":"https://github.com/pforhan","followers_url":"https://api.github.com/users/pforhan/followers","following_url":"https://api.github.com/users/pforhan/following{/other_user}","gists_url":"https://api.github.com/users/pforhan/gists{/gist_id}","starred_url":"https://api.github.com/users/pforhan/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/pforhan/subscriptions","organizations_url":"https://api.github.com/users/pforhan/orgs","repos_url":"https://api.github.com/users/pforhan/repos","events_url":"https://api.github.com/users/pforhan/events{/privacy}","received_events_url":"https://api.github.com/users/pforhan/received_events","type":"User","site_admin":false,"contributions":48},{"login":"eburke","id":63761,"node_id":"MDQ6VXNlcjYzNzYx","avatar_url":"https://avatars0.githubusercontent.com/u/63761?v=4","gravatar_id":"","url":"https://api.github.com/users/eburke","html_url":"https://github.com/eburke","followers_url":"https://api.github.com/users/eburke/followers","following_url":"https://api.github.com/users/eburke/following{/other_user}","gists_url":"https://api.github.com/users/eburke/gists{/gist_id}","starred_url":"https://api.github.com/users/eburke/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/eburke/subscriptions","organizations_url":"https://api.github.com/users/eburke/orgs","repos_url":"https://api.github.com/users/eburke/repos","events_url":"https://api.github.com/users/eburke/events{/privacy}","received_events_url":"https://api.github.com/users/eburke/received_events","type":"User","site_admin":false,"contributions":36},{"login":"dnkoutso","id":310370,"node_id":"MDQ6VXNlcjMxMDM3MA==","avatar_url":"https://avatars2.githubusercontent.com/u/310370?v=4","gravatar_id":"","url":"https://api.github.com/users/dnkoutso","html_url":"https://github.com/dnkoutso","followers_url":"https://api.github.com/users/dnkoutso/followers","following_url":"https://api.github.com/users/d
    <-- END HTTP (28135-byte body)

• 服务器返回数据示例

{
    "login": "JakeWharton",
    "id": 66577,
    "node_id": "MDQ6VXNlcjY2NTc3",
    "avatar_url": "https://avatars0.githubusercontent.com/u/66577?v=4",
    "gravatar_id": "",
    "url": "https://api.github.com/users/JakeWharton",
    "html_url": "https://github.com/JakeWharton",
    "followers_url": "https://api.github.com/users/JakeWharton/followers",
    "following_url": "https://api.github.com/users/JakeWharton/following{/other_user}",
    "gists_url": "https://api.github.com/users/JakeWharton/gists{/gist_id}",
    "starred_url": "https://api.github.com/users/JakeWharton/starred{/owner}{/repo}",
    "subscriptions_url": "https://api.github.com/users/JakeWharton/subscriptions",
    "organizations_url": "https://api.github.com/users/JakeWharton/orgs",
    "repos_url": "https://api.github.com/users/JakeWharton/repos",
    "events_url": "https://api.github.com/users/JakeWharton/events{/privacy}",
    "received_events_url": "https://api.github.com/users/JakeWharton/received_events",
    "type": "User",
    "site_admin": false,
    "contributions": 911
  }