如何从 Retrofit onResponse() 更新 Activity/Fragment UI？

Question

我想在我的下一个 Android 项目中使用 Retrofit 2.1.0。我想使用设计模式，因此为每个 REST 调用创建单独的类，即

IBalanceService.java

public Interface IBalanceService{
  @GET("users/{username}")
  void getUser(@Path("username") String username, Callback<User> cb);
}  

BalanceRestClient.java

public class BalanceRestClient{  

  String username = "Makarov";  

  Retrofit retrofit = new Retrofit.Builder()
                               .baseUrl("http://hovermind.com")
                               .addConverterFactory(GsonConverterFactory.create())
                               .addCallAdapterFactory(rxAdapter)
                               .build();  

  IBalanceService bs = retrofit.create(IBalanceService.class);


  Call<User> call = apiService.getUser(username);
  call.enqueue(new Callback<User>() {  

      @Override
      public void onResponse(Call<User> call, Response<User> response) {

          User user = response.body();  

          // update Activity/Fragment from here  

      }

      @Override
      public void onFailure(Call<User> call, Throwable t) {
        // Log error here since request failed
      }  

   });
}

BalanceActivity.java

public BalanceActivity extends Activity{

   // BalanceRestClient will update some UI elements 
}  

如何从 onResponse() 更新我的 Activity/fragment 中的 UI？

附加信息：
最小 SDK：19
目标 SDK：23
使用 OkHttp 和 gson 改造 2.1.0

Answer 1

制作这样的界面：

public interface BalanceListener {

    void onUserAvailable(User user);

}

在您的 BalanceRestClient 中有一个实例。而在 onResponse 中：

  @Override
  public void onResponse(Call<User> call, Response<User> response) {

      User user = response.body();  

      listener.onUserAvailable(user);

  }

让您的 Activity 实现 BalanceListner：

 public class BalanceActivity extends Activity implements BalanceListener {
                ......

        @Override
        public void onUserAvailable(User user) {
            // update user views here
        }
    }

Answer 2

 public class BalanceRestClient {

            private static BalanceRestClient instance;
            private IBalanceService request;

            private BalanceRestClient() {
                Retrofit retrofit = new Retrofit.Builder()
                        .baseUrl("http://hovermind.com")
                        .addConverterFactory(GsonConverterFactory.create())
                        .addCallAdapterFactory(rxAdapter)
                        .build();

                request = retrofit.create(IBalanceService.class);
            }

            public static synchronized BalanceRestClient getInstance() {
                if (instance == null)
                    instance = new BalanceRestClient();

                return instance;
            }

            public void getRequest(String userName, YourCustomeCallback callback) {

                Call<User> call = apiService.getUser(username);
                call.enqueue(new Callback<User>() {

                    @Override
                    public void onResponse(Call<User> call, Response<User> response) {

                        User user = response.body();

                        callback.onResponse(user);

                    }

                    @Override
                    public void onFailure(Call<User> call, Throwable t) {
                        // Log error here since request failed
                    }

                });
            }
        }

1. 创建一个单例类。它只发起一次请求。
2. 创建一个自定义回调，它将返回您对 UI 的响应。
3. 在您想使用它的地方调用 BalanceRestClient.getInstance.getRequest(params..)。