尝试访问API时发生空指针异常
我只是尝试retrofit2为我目前正在处理的新闻应用程序，我试图在片段类中调用我的API实现。 但我一直得到nullpointerexception，这是我的片段代码：
public class IgnFragment extends Fragment {
@BindView(R.id.ignNewsContainer)
RecyclerView ignNewsContainer;
Unbinder unbinder;
Call<NewsArticle> call;
public IgnFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_ign, container, false);
unbinder = ButterKnife.bind(this, view);
return view;
}
@Override
public void onStart() {
super.onStart();
call = NewsApi.getApi().getArticles("ign", "top");
getClient();
}
public void getClient(){
call.enqueue(new Callback<NewsArticle>() {
@Override
public void onResponse(Call<NewsArticle> call, Response<NewsArticle> response) {
NewsArticle newsArticle = response.body();
NewsAdapter newsAdapter = new NewsAdapter(newsArticle.getArticles(),getContext());
ignNewsContainer.setAdapter(newsAdapter);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getContext());
linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
ignNewsContainer.setLayoutManager(linearLayoutManager);
}
@Override
public void onFailure(Call<NewsArticle> call, Throwable t) {
t.printStackTrace();
Log.e("Error","Called");
}
});
}
@Override
public void onDestroyView() {
super.onDestroyView();
unbinder.unbind();
}
这里是我的api服务类：
public class NewsApi {
private static final String API_KEY = "________";
private static final String URL_BASE ="https://newsapi.org/v1/";
private static NewsService newsService =null;
public static NewsService getApi(){
if(newsService == null){
Retrofit retrofit= new Retrofit.Builder()
.baseUrl(URL_BASE)
.addConverterFactory(GsonConverterFactory.create())
.client(getClient())
.build();
NewsService api = retrofit.create(NewsService.class);
}
return newsService;
}
public static OkHttpClient getClient(){
HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
logging.setLevel(HttpLoggingInterceptor.Level.BODY);
OkHttpClient.Builder httpClient = new OkHttpClient.Builder();
return httpClient.addInterceptor(logging).build();
}
public interface NewsService{
@GET("articles?apiKey=" + API_KEY)
Call<NewsArticle> getArticles(@Query("source") String source,@Query("sortBy") String sortBy);
}
}
这是我得到的错误：
10-30 20：42：01.640 32640-32640 / cc.codemonkey.newsportal E / AndroidRuntime：致命异常：主进程：cc.codemonkey.newsportal，PID：32640 java.lang.NullPointerException：试图调用接口方法'retrofit2。调用cc.codemonkey.newsportal.fragments.IgnFragment.onStart上的空对象引用cc.codemonkey.newsportal.service.NewsApi $ NewsService.getArticles（java.lang.String，java.lang.String）'（IgnFragment.java： 54）at android.support.v4.app.Fragment.performStart（Fragment.java:2265）at android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1369）at android.support.v4.app.FragmentManagerImpl .moveFragmentToExpectedState（FragmentManager.java:1574）在android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1641）在android.support.v4.app.BackStackRecord.executeOps（BackStackRecord.java:794）在android。 support.v4.app.FragmentManagerImpl.executeOps（FragmentManager.java:2415）at android.support.v4.app.FragmentManagerImpl.executeOpsTogether（ FragmentManager.java:2200）at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps（FragmentManager.java:2153）at android.support.v4.app.FragmentManagerImpl.execSingleAction（FragmentManager.java:2034）at android.support.v4 .app.BackStackRecord.commitNowAllowingStateLoss（BackStackRecord.java:651）在android.support.v4.app.FragmentPagerAdapter.finishUpdate（FragmentPagerAdapter.java:143）在android.support.v4.view.ViewPager.populate（ViewPager.java:1239 ）在android.view.View.get.ViewPager.onMeasure（ViewPager.java:1613）android.view.View.measure（View。）上的android.support.v4.view.ViewPager.populate（ViewPager.java:1087）的java：17442）在android.widget.RelativeLayout.measureChildHorizontal（RelativeLayout.java:727）在android.widget.RelativeLayout.onMeasure（RelativeLayout.java:463）在android.view.View.measure（View.java:17442）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5463）at android.widget.FrameLayout.onMeasure（FrameLayout.java:430）at android.support.v7.widg et.ContentFrameLayout.onMeasure（ContentFrameLayout.java:139）在android.view.View.measure（View.java:17442）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5463）在android.widget.LinearLayout.measureChildBeforeLayout （LinearLayout.java:1436）at android.widget.LinearLayout.measureVertical（LinearLayout.java:722）at android.widget.LinearLayout.onMeasure（LinearLayout.java:613）at android.view.View.measure（View.java： （android.view.java:17442）android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5463）在android.widget.FrameLayout.onMeasure（FrameLayout.java:430）在android.view.View.measure（View.java:17442）。 view.ViewGroup.measureChildWithMargins（ViewGroup.java:5463）在android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1436）在android.widget.LinearLayout.measureVertical（LinearLayout.java:722）在android.widget.LinearLayout.onMeasure （LinearLayout.java:613）at android.view.View.measure（View.java:17442）at android.view.ViewGroup.measureChildWithMargins（Vi ewGroup.java:5463）at android.widget.FrameLayout.onMeasure（FrameLayout.java:430）at com.android.internal.policy.impl.PhoneWindow $ DecorView.onMeasure（PhoneWindow.java:2560）at android.view.View .measure（View.java:17442）在android.view.ViewRootImpl.performMeasure（ViewRootImpl.java:2001）在android.view.ViewRootImpl.measureHierarchy（ViewRootImpl.java:1166）在android.view.ViewRootImpl.performTraversals（ViewRootImpl。 Java的：1372）在android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1054）在android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:5779）在android.view.Choreographer $ CallbackRecord.run（Choreographer.java ：767）at android.view.Choreographer.doCallbacks（Choreographer.java:580）at android.view.Choreographer.doFrame（Choreographer.java:550）at android.view.Choreographer $ FrameDisplayEventReceiver.run（Choreographer.java:753） android.os.Handler.handleCallback（Handler.java:739）在android.os.Handler.dispatchMessage（Handler.java:95）android.os.Looper.loop（Looper.java： 135）at android.app.ActivityThread.main（ActivityThread.java:5253）at java.lang。
你的问题是在这个确切的路线
NewsAdapter newsAdapter = new NewsAdapter(newsArticle.getArticles(),getContext());
问题说新闻文章在这里已经初始化为null
NewsArticle newsArticle = response.body();
所以response.body()为null请尝试调试，并看看它为什么是空的！ 当你解决这个问题时你的解决方案应该可以工 而且alos指的是什么是NullPointerException，我该如何解决它？ 了解更多NullPointerException是什么。