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java – Android Volley Null Pointer Exception

Posted by: admin May 14, 2020 Leave a comment

Questions:

I’m attempting to convert a previously Activity-based tutorial to a Fragment, but I continue to run into the NullPointerException error on my Adapter.

The tutorial is based on this and I have slimmed down the constructor for the Adapter because it used to be calling an Activity.

There is one possible solution here but nobody knows how to proceed with the same possible question.

I want to convert everything to a working Fragment. Please let me know if you need more information from me.

Main converted class:

public class mainViewController2 extends Fragment {
    private static final String TAG = mainViewController2.class.getSimpleName();
    private ListView listView;
    private FeedListAdapter listAdapter;
    private List<FeedItem> feedItems;
    private String URL_FEED = "http://api.androidhive.info/feed/feed.json";

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

        View v = inflater.inflate(R.layout.mainviewcontroller2_fragment, container, false);

        listView = (ListView) v.findViewById(R.id.list);

        feedItems = new ArrayList<FeedItem>();


        //where the error shows up?
        listAdapter = new FeedListAdapter(feedItems);
        listView.setAdapter(listAdapter);



        // We first check for cached request
        Cache cache = AppController.getInstance().getRequestQueue().getCache();
        Entry entry = cache.get(URL_FEED);
        if (entry != null) {
            // fetch the data from cache
            try {
                String data = new String(entry.data, "UTF-8");
                try {
                    parseJsonFeed(new JSONObject(data));
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }

        } else {
            // making fresh volley request and getting json
            JsonObjectRequest jsonReq = new JsonObjectRequest(Method.GET,
                    URL_FEED, null, new Response.Listener<JSONObject>() {

                        @Override
                        public void onResponse(JSONObject response) {
                            VolleyLog.d(TAG, "Response: " + response.toString());
                            if (response != null) {
                                parseJsonFeed(response);
                            }
                        }
                    }, new Response.ErrorListener() {

                        @Override
                        public void onErrorResponse(VolleyError error) {
                            VolleyLog.d(TAG, "Error: " + error.getMessage());
                        }
                    });

            // Adding request to volley request queue
            AppController.getInstance().addToRequestQueue(jsonReq);
        }

        return v;
    }

    /**
     * Parsing json reponse and passing the data to feed view list adapter
     * */
    private void parseJsonFeed(JSONObject response) {
        try {
            JSONArray feedArray = response.getJSONArray("feed");

            for (int i = 0; i < feedArray.length(); i++) {
                JSONObject feedObj = (JSONObject) feedArray.get(i);

                FeedItem item = new FeedItem();
                item.setId(feedObj.getInt("id"));
                item.setName(feedObj.getString("name"));

                // Image might be null sometimes
                String image = feedObj.isNull("image") ? null : feedObj
                        .getString("image");
                item.setImge(image);
                item.setStatus(feedObj.getString("status"));
                item.setProfilePic(feedObj.getString("profilePic"));
                item.setTimeStamp(feedObj.getString("timeStamp"));

                // url might be null sometimes
                String feedUrl = feedObj.isNull("url") ? null : feedObj
                        .getString("url");
                item.setUrl(feedUrl);

                feedItems.add(item);
            }

            // notify data changes to list adapater
            listAdapter.notifyDataSetChanged();
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

FeedListAdapter:

 public class FeedListAdapter extends BaseAdapter { 
    private Activity activity;
    private LayoutInflater inflater;
    private List<FeedItem> feedItems;

    Context context;

    ImageLoader imageLoader;

     public FeedListAdapter(Context ctx,List<FeedItem> feedItems) {
        this.context= ctx;
        this.feedItems = feedItems;
        imageLoader = AppController.getInstance().getImageLoader();
        inflater = LayoutInflater.from(context);
     }

    @Override
    public int getCount() {
        return feedItems.size();
    }

    @Override
    public Object getItem(int location) {
        return feedItems.get(location);
    }
        @Override
        public long getItemId(int position) {
            return position;
        }

        @SuppressLint("InflateParams")
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            if (inflater == null)
                inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            if (convertView == null)
                convertView = inflater.inflate(R.layout.feed_item, null);

            if (imageLoader == null)
                imageLoader = AppController.getInstance().getImageLoader();

            TextView name = (TextView) convertView.findViewById(R.id.name);
            TextView timestamp = (TextView) convertView
                    .findViewById(R.id.timestamp);
            TextView statusMsg = (TextView) convertView
                    .findViewById(R.id.txtStatusMsg);
            TextView url = (TextView) convertView.findViewById(R.id.txtUrl);
            NetworkImageView profilePic = (NetworkImageView) convertView
                    .findViewById(R.id.profilePic);
            FeedImageView feedImageView = (FeedImageView) convertView
                    .findViewById(R.id.feedImage1);

            FeedItem item = feedItems.get(position);

            name.setText(item.getName());

            // Converting timestamp into x ago format
            CharSequence timeAgo = DateUtils.getRelativeTimeSpanString(
                    Long.parseLong(item.getTimeStamp()),
                    System.currentTimeMillis(), DateUtils.SECOND_IN_MILLIS);
            timestamp.setText(timeAgo);

            // Chcek for empty status message
            if (!TextUtils.isEmpty(item.getStatus())) {
                statusMsg.setText(item.getStatus());
                statusMsg.setVisibility(View.VISIBLE);
            } else {
                // status is empty, remove from view
                statusMsg.setVisibility(View.GONE);
            }

            // Checking for null feed url
            if (item.getUrl() != null) {
                url.setText(Html.fromHtml("<a href=\"" + item.getUrl() + "\">"
                        + item.getUrl() + "</a> "));

                // Making url clickable
                url.setMovementMethod(LinkMovementMethod.getInstance());
                url.setVisibility(View.VISIBLE);
            } else {
                // url is null, remove from the view
                url.setVisibility(View.GONE);
            }

            // user profile pic
            profilePic.setImageUrl(item.getProfilePic(), imageLoader);

            // Feed image
            if (item.getImge() != null) {
                feedImageView.setImageUrl(item.getImge(), imageLoader);
                feedImageView.setVisibility(View.VISIBLE);
                feedImageView
                        .setResponseObserver(new FeedImageView.ResponseObserver() {
                            @Override
                            public void onError() {
                            }

                            @Override
                            public void onSuccess() {
                            }
                        });
            } else {
                feedImageView.setVisibility(View.GONE);
            }

            return convertView;
        }

    }

LogCat errors:

09-06 02:51:55.823: E/AndroidRuntime(8279): FATAL EXCEPTION: main
09-06 02:51:55.823: E/AndroidRuntime(8279): Process: com.rynovation.kline, PID: 8279
09-06 02:51:55.823: E/AndroidRuntime(8279): java.lang.NullPointerException
09-06 02:51:55.823: E/AndroidRuntime(8279):     at androidFeedClasses.FeedListAdapter.<init>(FeedListAdapter.java:35)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at com.rynovation.kline.mainViewController2.onCreateView(mainViewController2.java:51)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at android.app.Fragment.performCreateView(Fragment.java:1700)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:890)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at android.app.BackStackRecord.run(BackStackRecord.java:684)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1453)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at android.os.Handler.handleCallback(Handler.java:733)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at android.os.Handler.dispatchMessage(Handler.java:95)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at android.os.Looper.loop(Looper.java:146)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at android.app.ActivityThread.main(ActivityThread.java:5487)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at java.lang.reflect.Method.invokeNative(Native Method)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at java.lang.reflect.Method.invoke(Method.java:515)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
09-06 02:51:55.823: E/AndroidRuntime(8279):     at dalvik.system.NativeStart.main(Native Method)
How to&Answers:

I guess you missed a simple code in your manifest file. Your AppController package extends Application , So the application tag in your manifest is searching for the AppController but isn’t able to find.

Just Write this simple code in your AndroidManifest.xml

android:name = your.package.AppController

Answer:

A little late maybe, but a representative answer to user3902144’s answer:

Similar Answer to this question : Link

You may have missed out this from your manifest:

 <application
        android:name="<package-name>.app.AppController" // <-- this one
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme">

That’s why onCreate never called and mInstance is null.

Hope this helps 🙂

Answer:

Looking at the error, it seems like you’re calling getActivity() inside onCreateView(). You should be getting the activity in onActivityCreated instead where it shouldn’t be null.

Answer:

Change this from

listView = (ListView) getActivity().findViewById(R.id.list);

to

listView = (ListView)v.findViewById(R.id.list);

This is because getActivity() is generally used for as a Context in Fragment. While you’r find id for your UI elements in Fragment then you have to give reference of your View's object which will be returned in onCreateView() method.

Update:

Change your Adapter Like,

listAdapter = new FeedListAdapter(getActivity(),feedItems);

Now in its Constructor

 ImageLoader imageLoader;

 public FeedListAdapter(Context ctx,List<FeedItem> feedItems) {
    this.context= ctx;
    this.feedItems = feedItems;
    imageLoader = AppController.getInstance().getImageLoader()
 }

Now in your adapter class use context variable as a Context.

Answer:

Please check all your params carefully, make sure not to send any null value in params, if using some stored values then use the condition like below:

@Override
protected Map<String, String> getParams() {
 Map<String, String> params = new HashMap<String, String>();
 if(paramValue!= null)
     params.put("paramKey", paramValue);
  else
     params.put("paramKey", "anyOtherDefaultValue");
 return params;
 }