public class AsyncGet {
  public static void main(String[] args) throws IOException {
  OkHttpClient client = new OkHttpClient();

  Request request = new Request.Builder()
      .url("http://www.baidu.com")
      .build();

  client.newCall(request).enqueue(new Callback() {
    public void onFailure(Request request, IOException e) {
      e.printStackTrace();
    }

    public void onResponse(Response response) throws IOException {
      if (!response.isSuccessful()) {
        throw new IOException("服务器端错误: " + response);
      }

      System.out.println(response.body().string());
    }
});
  }
}

/* 以fragment为例 */

public class BaseFragment extends Fragment implements Handler.Callback {

private static final int MSG_QUERY_DATA = 0x00;
private static final int MSG_DISPLAY_DATA = 0x01;

@Override
public void onAttach(Activity activity) {
  super.onAttach(activity);
  this.activity = activity;

  /* setup handler */
  HandlerThread handlerThread = new HandlerThread(getClass().getName());
  handlerThread.start();
  backgroundHandler = new Handler(handlerThread.getLooper(), this);
  uiHandler = new Handler(activity.getMainLooper(), this);
}

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {

  /* start */
  backgroundHandler.sendEmptyMessage(MSG_QUERY_DATA);
}

@Override
public void onDestroyView() {

  /* 將Message清空，backgroundThread結束掉 */
  backgroundHandler.removeCallbacksAndMessages(null);
  uiHandler.removeCallbacksAndMessages(null);
  backgroundHandler.getLooper().quit();
  super.onDestroyView();
}

@Override
public boolean handleMessage(Message msg) {

  /* 如果fragment不在Activity上了，直接return掉，避免NPE */
  if (!isAdded()) return false;

  /* 做各種MSG */
  switch(msg.what){

    case MSG_QUERY_DATA:

      // do okHttp without callback
      Response response = client.newCall(request).execute();

      // 傳回 uiThread 做UI更新
      Message respMsg = uiHandler.obtainMessage();
      respMsg.what = MSG_DISPLAY_DATA;
      respMsg.obj = response;
      backgroundHandler.sendMessage(respMsg);
      break;

    case MSG_DISPLAY_DATA:

      Response apiResponse = (Response)msg.obj;

      // 失敗
      if(null == apiResponse){
        //show error
      }

      // 成功
      else{
        //display data on UI
      }

      break;

    return false;
  }
}