我已经从developer.android.com复制了volleySingleton代码，并尝试在回收站视图中从URL获取图像，但是在加载数据应用程序崩溃时 . 我已经尝试了一些修复，但它们没有用
这是从developer.android.com复制的volleySingleton类
public class MyApplication extends Application {
private static MyApplication mInstance;
private RequestQueue mRequestQueue;
private ImageLoader mImageLoader;
private static Context mCtx;
private MyApplication(Context context) {
mCtx = context;
mRequestQueue = getRequestQueue();
mImageLoader = new ImageLoader(mRequestQueue,
new ImageLoader.ImageCache() {
private final LruCache<String, Bitmap>
cache = new LruCache<String, Bitmap>(20);
@Override
public Bitmap getBitmap(String url) {
return cache.get(url);
}
@Override
public void putBitmap(String url, Bitmap bitmap) {
cache.put(url, bitmap);
}
});
}
public static synchronized MyApplication getInstance(Context context) {
if (mInstance == null) {
mInstance = new MyApplication(context);
}
return mInstance;
}
public RequestQueue getRequestQueue() {
if (mRequestQueue == null) {
// getApplicationContext() is key, it keeps you from leaking the
// Activity or BroadcastReceiver if someone passes one in.
mRequestQueue = Volley.newRequestQueue(mCtx.getApplicationContext());
}
return mRequestQueue;
}
public <T> void addToRequestQueue(Request<T> req) {
getRequestQueue().add(req);
}
public ImageLoader getImageLoader() {
return mImageLoader;
}
}
这是logcat报告
com.aninesoft.meltwishbeta.MyApplication.getRequestQueue（MyApplication.java:61）中的com.aninesoft.meltwishbeta.MyApplication . （MyApplication.java:31）com.aninesoft.meltwishbeta.MyApplication.getInstance中的java.lang.NullPointerException（ MyApplication.java:52）com.aninesoft.meltwishbeta.RecyclerViewDataAdapter.onBindViewHolder（RecyclerViewDataAdapter.java:45）at com.aninesoft.meltwishbeta.RecyclerViewDataAdapter.onBindViewHolder（RecyclerViewDataAdapter.java:19）at android.support.v7.widget.RecyclerView $ adapter.onBindViewHolder（RecyclerView.java:5277）在android.support.v7.widget.RecyclerView $ Adapter.bindViewHolder（RecyclerView.java:5310）在android.support.v7.widget.RecyclerView $ Recycler.getViewForPosition（RecyclerView.java） ：4568）在android.support的android.support.v7.widget.RecyclerView $ Recycler.getViewForPosition（RecyclerView.java:4461）android.support.v7.widget.LinearLayoutManager $ LayoutState.next（LinearLayoutManager.java:1962） . v7.widget.LinearLayoutManager.layoutChunk（林earLayoutManager.java:1371）在android.support.v7上的android.support.v7.widget.LineoutLayoutManager.fill（LinearLayoutManager.java:1334）android.support.v7.widget.LinearLayoutManager.onLayoutChildren（LinearLayoutManager.java:563） .widget.RecyclerView.dispatchLayout（RecyclerView.java:2847）在Android的android.view.View.layout（View.java:14832）上的android.support.v7.widget.RecyclerView.onLayout（RecyclerView.java:3145） . android.widget.Lineout.ayLayout.onLayout上的android.widget.LinearLayout.setoutVertical（LinearLayout.java:1525）上的android.widget.LinearLayout.setChildFrame（LinearLayout.java:1671）中的view.ViewGroup.layout（ViewGroup.java:4640） （LinearLayout.java:1434）在android.view.View.layout（View.java:14832）的android.view.ViewGroup.layout（ViewGroup.java:4640）android.support.v4.view.ViewPager.onLayout（ ViewPager.java:1627）在android.view.View.layout（View.java:14832）的android.view.ViewGroup.layout（ViewGroup.java:4640）android.support.design.widget.CoordinatorLayout.layoutChild（Coord） inatorLayout.java:1034）android.support.design.widget.CoordinatorLayout.onLayoutChild（CoordinatorLayout.java:744）在android.support.design的android.support.design.widget.ViewOffsetBehavior.onLayoutChild（ViewOffsetBehavior.java:42） .widget.AppBarLayout $ ScrollingViewBehavior.onLayoutChild（AppBarLayout.java:1180）位于android.view.View.layout（View.java:14832）的android.support.design.widget.CoordinatorLayout.onLayout（CoordinatorLayout.java:757）在Android.view.View.View的android.widget.FrameLayout.onLayout（FrameLayout.java:388）android.widget.FrameLayout.layoutChildren（FrameLayout.java：453）的android.view.ViewGroup.layout（ViewGroup.java:4640） .layout（View.java:14832）在Android.view上的android.sview.v7 . 内部 . 管理程序中的android.sview.v7.internal.widget.ActionBarOverlayLayout.onLayout（ActionBarOverlayLayout.java:437） . 在Android.widget.FrameLayout.layoutChildren（FrameLayout.java:453）的android.view.ViewGroup.layout（ViewGroup.java:4640）上的View.layout（View.java:14832）在Android.widget上的android.view.View.Loutout（FrameLayout.java:388）android.view.Viewout上的android.view.View.layout（View.java:14832）的android.w. Linear.wayout.setChildFrame（LinearLayout.java:1671）在Android.widget.Line中的android.widget.LinearLayout.onLayout（LinearLayout.java：1434）处于android.view.Loutout.Loutout（DirectLayout.java：1434） .java：14832）在Android.widget.FrameLayout.onLayout（FrameLayout.java:388）的android.widget.FrameLayout.layoutChildren（FrameLayout.java：453）的android.view.ViewGroup.layout（ViewGroup.java:4640）在Android.view上的android.view.View.Loutout（ViewRootImpl.java:1996）的android.view.View.layout（ViewGroup.java:4640）上的android.view.View.layout（View.java:14832） . 在android.view.ViewRootImpl $的android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1004）上的ViewRootImpl.performTraversals（ViewRootImpl.java:1753）
这是适配器类
public class RecyclerViewDataAdapter extends RecyclerView.Adapter<RecyclerViewDataAdapter.ViewHolder> {
private Context context;
public ImageLoader mImageLoader;
//List of superHeroes
List<ListOfData> superHeroes;
public RecyclerViewDataAdapter(List<ListOfData> superHeroes, Context context){
super();
//Getting all the superheroes
this.superHeroes = superHeroes;
this.context=context;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext())
.inflate(R.layout.recyclerview_row, parent, false);
ViewHolder viewHolder = new ViewHolder(v);
return viewHolder;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
ListOfData superHero = superHeroes.get(position);
mImageLoader = MyApplication.getInstance(context).getImageLoader();
mImageLoader.get(superHero.getImageUrl(), ImageLoader.getImageListener(holder.imageView1, R.mipmap.ic_launcher, android.R.drawable.ic_dialog_alert));
holder.imageView1.setImageUrl(superHero.getImageUrl(), mImageLoader);
holder.textViewName1.setText(superHero.getName());
//holder.textViewRank.setText(String.valueOf(superHero.getRank()));
//holder.textViewRealName.setText(superHero.getRealName());
//holder.textViewCreatedBy.setText(superHero.getCreatedBy());
//holder.textViewFirstAppearance.setText(superHero.getFirstAppearance());
String powers = "";
/* for(int i = 0; i<superHero.getPowers().size(); i++){
powers+= superHero.getPowers().get(i);
}*/
//holder.textViewPowers.setText(powers);
}
@Override
public int getItemCount() {
return superHeroes.size();
}
class ViewHolder extends RecyclerView.ViewHolder{
public NetworkImageView imageView1;
public NetworkImageView imageView2;
public TextView textViewName1;
public TextView textViewName2;
public TextView textViewRank;
public TextView textViewRealName;
public TextView textViewCreatedBy;
public TextView textViewFirstAppearance;
public TextView textViewPowers;
public ViewHolder(View itemView) {
super(itemView);
imageView1 = (NetworkImageView) itemView.findViewById(R.id.imageViewHero);
//imageView2 = (NetworkImageView) itemView.findViewById(R.id.thumbnail2);
textViewName1 = (TextView) itemView.findViewById(R.id.textViewName);//textViewName2 = (TextView) itemView.findViewById(R.id.category_title_two);
/* textViewRank= (TextView) itemView.findViewById(R.id.textViewRank);
textViewRealName= (TextView) itemView.findViewById(R.id.textViewRealName);
textViewCreatedBy= (TextView) itemView.findViewById(R.id.textViewCreatedBy);
textViewFirstAppearance= (TextView) itemView.findViewById(R.id.textViewFirstAppearance);
textViewPowers= (TextView) itemView.findViewById(R.id.textViewPowers);
*/
}
}
}
and Json part
public class Pants extends Fragment {
//Creating a List of superheroes
public Context context;
public List<ListOfData> listSuperHeroes;
//Creating Views
private RecyclerView recyclerView;
private RecyclerView.LayoutManager layoutManager;
private RecyclerView.Adapter adapter;
public Pants() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.tshirts_pants_shirts, container, false);
recyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
layoutManager = new LinearLayoutManager(getActivity().getApplicationContext());
recyclerView.setLayoutManager(layoutManager);
//Calling method to get data
getData();
return view;
}
private void getData() {
//Showing a progress dialog
final ProgressDialog loading = ProgressDialog.show(getActivity(), "Loading Data", "Please wait...", false, false);
//Creating a json array request
JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(ProductConfig.DATA_URL,
new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
//Dismissing progress dialog
loading.dismiss();
//calling method to parse json array
parseData(response);
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
//Creating request queue
RequestQueue requestQueue = Volley.newRequestQueue(getActivity());
//Adding request to the queue
requestQueue.add(jsonArrayRequest);
}
//This method will parse json data
private void parseData(JSONArray array) {
listSuperHeroes = new ArrayList<>();
for (int i = 0; i < array.length(); i++) {
ListOfData superHero = new ListOfData();
JSONObject json = null;
try {
json = array.getJSONObject(i);
superHero.setImageUrl(json.getString(ProductConfig.TAG_IMAGE_URL));
superHero.setName(json.getString(ProductConfig.TAG_NAME));
/*superHero.setRank(json.getInt(ProductConfig.TAG_RANK));
superHero.setRealName(json.getString(ProductConfig.TAG_REAL_NAME));
superHero.setCreatedBy(json.getString(ProductConfig.TAG_CREATED_BY));
superHero.setFirstAppearance(json.getString(ProductConfig.TAG_FIRST_APPEARANCE));
*/
ArrayList<String> powers = new ArrayList<String>();
JSONArray jsonArray = json.getJSONArray(ProductConfig.TAG_POWERS);
for (int j = 0; j < jsonArray.length(); j++) {
powers.add(((String) jsonArray.get(j)) + "\n");
}
superHero.setPowers(powers);
} catch (JSONException e) {
e.printStackTrace();
}
listSuperHeroes.add(superHero);
}
adapter = new RecyclerViewDataAdapter(listSuperHeroes, context);
//Adding adapter to recyclerview
recyclerView.setAdapter(adapter);
//Initializing our superheroes list
}
}