Android 对服务器的 GET 改造 API 调用失败答案

【问题标题】：Android failed GET retrofit API call to serverAndroid 对服务器的 GET 改造 API 调用失败
【发布时间】：2016-04-05 21:09:18
【问题描述】：

我正在开发一个 Android 项目。我正在使用改造来调用 API。所以我正在做一个 API 调用来获取与证书相关的课程列表。

来自服务器的响应 get (BASE_URL/certificates/1) 是：

{
  "id": 1,
  "name": "Arts-certificate",
  "authorized_by": "priya",
  "created_by": "self",
  "created_by_id": "1",
  "description": "awarded to the best",
  "doc_url": "http://f8rentals.com/wp-content/uploads/2015/03/IMG_0067ft.jpg?189db0",
  "category_id": "2",
  "cateogory": "Arts",
  "courses": [
    {
      "id": 1,
      "course_id": "CRSXQHGZ0SCTLhklhk6JL",
      "number_of_sessions": 1,
      "created_at": "2015-12-16T07:10:37.000+00:00",
      "updated_at": "2015-12-16T07:10:37.000+00:00",
      "tags": null
    },
    {
      "id": 1,
      "course_id": "CRSXQHGZ0SCTLhklhk6JL",
      "number_of_sessions": 1,
      "created_at": "2015-12-16T07:10:37.000+00:00",
      "updated_at": "2015-12-16T07:10:37.000+00:00",
      "tags": null
    }
    .
    .
    .
    .
  ]
}

我有证书列表，需要采取的措施是，单击证书后，它应该进入新片段，其中包含与该证书关联的所有课程（点击该证书）。为此，我进行了上述 API 调用。

问题是当我单击列表中的第一个证书时，它会转到下一个片段并列出所有课程。但是当我单击任何其他证书时，它会显示空白片段。当我调试代码时，在 fetchCourses() CoursesListOfCertificatesFragment.java 中，调用了 onFailure() 函数。

Workflow 是 CertificateFragment 是列出所有证书的类。单击时，CertificateFragment 中的 CertificateClickListner() 会被触发，并依次启动 CoursesListOfCertificatesFragment 并在此片段的构造函数中传递证书对象。在这里，我进行 API 调用 GET (BASE_URL/certificates/1)。

这是在 CoursesListOfCertificatesFragment 的 fetchCourses() 中。但除了第一个证书，onFailure() 方法被调用。

感谢任何帮助.....如果需要任何其他信息，请询问。

谢谢。

以下是列出的相关类：

CoursesListOfCertificatesFragment.java

package com.localjini.learner.fragments;

import android.os.Bundle;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ProgressBar;
import android.widget.TextView;

import com.localjini.learner.R;
import com.localjini.learner.adapters.CourseListingRVAdapter;
import com.localjini.learner.api.RestClient;
import com.localjini.learner.main.HomeActivity;
import com.localjini.learner.models.Certificates;
import com.localjini.learner.models.Course;
import com.localjini.learner.models.CoursesResponse;
import com.localjini.learner.models.GetCertificateResponse;
import com.localjini.learner.utils.LogUtils;
import com.localjini.learner.utils.UIHelper;

import java.util.List;

import butterknife.Bind;
import butterknife.ButterKnife;
import retrofit.Call;
import retrofit.Callback;
import retrofit.Response;
import retrofit.Retrofit;


public class CoursesListOfCertificatesFragment extends BaseFragment {

    @Bind(R.id.tv_category)
    TextView tvCategory;
    @Bind(R.id.tv_sort_filter)
    TextView tvSortFilter;
    @Bind(R.id.pb_course_listing)
    ProgressBar pbCourseListing;
    @Bind(R.id.rv_course_listing)
    RecyclerView rvCourseListing;

    public UIHelper uiHelper;
    List<Course> courses;

    private Certificates certificate;
    private int certificate_id;

    public CoursesListOfCertificatesFragment(){

    }

    private CourseListingRVAdapter.CourseClickListener listener = new CourseListingRVAdapter.CourseClickListener() {

        @Override
        public void onCourseClicked(Course course) {
            interactionListener.launchCourseDetailFragment();
        }
    };

    public CoursesListOfCertificatesFragment(Certificates certificate){
        this.certificate = certificate;
        this.certificate_id = certificate.getId();
    }

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    }

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        if (root == null) {
            root = (ViewGroup) inflater.inflate(R.layout.fragment_course_listing, container, false);

            ButterKnife.bind(this, root);

            initInstances();

            fetchCourses();
        }


        return root;
    }

    private void initInstances() {
        uiHelper = new UIHelper(getActivity());

        ((HomeActivity) getActivity()).getSupportActionBar().setHomeButtonEnabled(true);
        ((HomeActivity) getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        ((HomeActivity) getActivity()).getSupportActionBar().setTitle("");

        rvCourseListing.setItemAnimator(new DefaultItemAnimator());
        rvCourseListing.setLayoutManager(new LinearLayoutManager(getActivity()));
        rvCourseListing.setHasFixedSize(true);
    }

    private void fetchCourses() {
        Call<GetCertificateResponse> call = RestClient.getCMSServiceInstance().getCertificateById(certificate_id);
        call.enqueue(new Callback<GetCertificateResponse>() {
            @Override
            public void onResponse(Response<GetCertificateResponse> response, Retrofit retrofit) {

                if (response != null) {
                    GetCertificateResponse resp = response.body();

                    if (resp != null) {
                        showCourses(resp.getCourses());
                    } else {
                        uiHelper.showToast("response contain null data");
                    }
                }
            }

            @Override
            public void onFailure(Throwable t) {
                LogUtils.d("coursesFailed", t.getMessage());
            }
        });

    }

    private void showCourses(List<Course> courses) {
        if(courses != null) {
            CourseListingRVAdapter courseListingRVAdapter = new CourseListingRVAdapter(getActivity(), courses);
            courseListingRVAdapter.setCourseClickListener(listener);
            rvCourseListing.setAdapter(courseListingRVAdapter);
        }
    }

    public FragmentId getFragmentId() {
        return FragmentId.COURSE_LISTING_FRAGMENT;
    }

}

CertificateFragment.java

public class CertificateFragment extends BaseFragment {

    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";
    //protected ViewGroup root;
    protected Context context;
    @Bind(R.id.rv_Certificates) RecyclerView rvCertificates;

    private CertificateRVAdapter.CertificateClickListener listener = new CertificateRVAdapter.CertificateClickListener() {

        @Override
        public void onCertificateClicked(Certificates certificate) {
            Toast.makeText(getActivity(), certificate.getName() +" Clicked", Toast.LENGTH_SHORT).show();
            //interactionListener.launchCourseListingFragment();
            interactionListener.launchCoursesListOfCertificatesFragment(certificate);
        }
    };


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        if(root==null) {

            root = (ViewGroup) inflater.inflate(R.layout.fragment_certificate, container, false);
            ButterKnife.bind(this, root);

            initInstances();
            getCertificates();
        }
        return root;
    }
//    rvCourseListing.setItemAnimator(new DefaultItemAnimator());
//    rvCourseListing.setLayoutManager(new LinearLayoutManager(getActivity()));
//    rvCourseListing.setHasFixedSize(true);
//

    private void initInstances() {
        //uiHelper = new UIHelper(getActivity());

        ((HomeActivity) getActivity()).getSupportActionBar().setHomeButtonEnabled(true);
        ((HomeActivity) getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        ((HomeActivity) getActivity()).getSupportActionBar().setTitle("");

        rvCertificates.setItemAnimator(new DefaultItemAnimator());
        rvCertificates.setLayoutManager(new LinearLayoutManager(getActivity()));
        rvCertificates.setHasFixedSize(true);
    }

    private void getCertificates() {

        Call<AllCertificateResponse> call = RestClient.getCMSServiceInstance().getCertificates();

        call.enqueue(new Callback<AllCertificateResponse>() {
            @Override
            public void onResponse(Response<AllCertificateResponse> response, Retrofit retrofit) {
                if (response.isSuccess()) {
                    //com.squareup.okhttp.Response raw = response.body().raw();

                    List<Certificates> certificates = response.body().getCertificates();
                    if (certificates != null)
                        showCertificates(certificates);

                    Toast.makeText(getActivity(), "Success in getting certificates", Toast.LENGTH_SHORT).show();
                } else {
                    Log.d("CERT", "response is failure");
                }
            }

            @Override
            public void onFailure(Throwable t) {
                Toast.makeText(getActivity(), "Failure", Toast.LENGTH_SHORT).show();
            }

        });
    }

    public void showCertificates(List<Certificates> certificates){

        CertificateRVAdapter adapter = new CertificateRVAdapter(getActivity(), certificates);
        adapter.setCertificateClickListener(listener);
        rvCertificates.setAdapter(adapter);
    }

    public FragmentId getFragmentId() {
        return FragmentId.COURSE_LISTING_FRAGMENT;
    }

}

【问题讨论】：

标签： java android android-fragments retrofit

【解决方案1】：

我解决了这个问题。原来服务器给出了错误的响应（它仍处于测试阶段）。我期待字符串数组。虽然对于第一个证书，所有课程都有字符串数组，但对于第二个证书，所有课程都有字符串值而不是数组。

【讨论】：