如何从Retrofit onResponse（）更新活动/片段UI？

 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。它只初始化一次请求。
2. 创建一个自定义回调，它将使您的响应返回给UI。
3. 在要使用它的地方调用BalanceRestClient.getInstance.getRequest（params ..）。