NullPointer exception in setAdapter in ListView

Question

when wifi is on - all works, but when it off - i get nullPointer exception

package ua.khuta.myskidka;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.database.Cursor;
import android.graphics.Color;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.Fragment;

import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;

public class FragmentNews extends Fragment {
private View v;
ListView lvNews;
Database db;
mySCadapter scAdapter;
public String DEBUG_TAG = "myLogs";
String[] from = new String[] { Database.NEWS_TITLE, Database.NEWS_IMAGE_URL,
        Database.NEWS_SHORT_DESCRIPTION };
int [] to = new int[] { R.id.item_news_tv_title, R.id.item_news_iv_image,
        R.id.item_news_tv_short_description };



@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    v = inflater.inflate(R.layout.fragment_news, null);
    lvNews = (ListView) v.findViewById(R.id.lv_new);
    lvNews.setCacheColorHint(Color.TRANSPARENT);

    return v;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    db = Database.getInstance(getActivity());

    ConnectivityManager connManager = (ConnectivityManager) getActivity()
            .getSystemService(getActivity().CONNECTIVITY_SERVICE);
    NetworkInfo mWifi = connManager
            .getNetworkInfo(ConnectivityManager.TYPE_WIFI);

    if (mWifi.isConnected()) {
        Log.d(DEBUG_TAG, "wi-fi is on");
        db.cleanDB();
        GetJSON getJSON = new GetJSON();
        getJSON.execute();
    } else {

        Log.d(DEBUG_TAG, "wi-fi is off");

        Cursor c = db.getNewsFromDb();
        Log.d(DEBUG_TAG, String.valueOf(c.getCount()));
         mySCadapter scAdapter = new mySCadapter(getActivity(), R.layout.item_news, c,
                from, to);

        lvNews.setAdapter(scAdapter);
    }

}



class GetJSON extends AsyncTask<Void, Void, Void> {

    @Override
    protected Void doInBackground(Void... params) {
        // Creating JSON Parser instance

        return null;
    }

    @Override
    protected void onPostExecute(Void result) {

        Cursor c = db.getNewsFromDb();
        scAdapter = new mySCadapter(getActivity(), R.layout.item_news, c,
                from, to);

        lvNews.setAdapter(scAdapter);

        super.onPostExecute(result);
    }

}

}

ErrorLog

    10-10 09:12:53.275: E/AndroidRuntime(28582): FATAL EXCEPTION: main
10-10 09:12:53.275: E/AndroidRuntime(28582): java.lang.RuntimeException: Unable to start activity ComponentInfo{ua.khuta.myskidka/ua.khuta.myskidka.MainActivity}: java.lang.NullPointerException
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.app.ActivityThread.access$600(ActivityThread.java:141)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.os.Handler.dispatchMessage(Handler.java:99)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.os.Looper.loop(Looper.java:137)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.app.ActivityThread.main(ActivityThread.java:5103)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at java.lang.reflect.Method.invokeNative(Native Method)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at java.lang.reflect.Method.invoke(Method.java:525)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at dalvik.system.NativeStart.main(Native Method)
10-10 09:12:53.275: E/AndroidRuntime(28582): Caused by: java.lang.NullPointerException
10-10 09:12:53.275: E/AndroidRuntime(28582):    at ua.khuta.myskidka.FragmentNews.onCreate(FragmentNews.java:82)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.support.v4.app.Fragment.performCreate(Fragment.java:1455)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:893)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1460)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:556)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.app.Activity.performStart(Activity.java:5143)
10-10 09:12:53.275: E/AndroidRuntime(28582):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
10-10 09:12:53.275: E/AndroidRuntime(28582):    ... 11 more

Answer 1

the problem is that you are creating your ListView in onCreateView() and setting its adapter in onCreate() ..

you should know that onCreate() is always called before onCreateView() and by that time your listview is not being created .. thats why you are getting NullPointerException.

Place your code of onCreate() in onCreateView()

Answer 2

The problem is that you are creating your ListView in another layout file while you are calling any other layout file in same activity .So its mismatch in layout calling the activity.So place ListView in same layout that your activity using or if you want ListView in another layout then change ArrayAdapter object context e.g.: change it to

ArrayAdapter adapter = new ArrayAdapter(this, R.layout., R.id., );

with this:

ArrayAdapter adapter = new ArrayAdapter(, R.layout., R.id., );

Answer 3

Just put your listview code on onViewCreated callback

Try this code:

Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle saveInstanceState) {
    return inflater.inflate(R.layout.fragment_news, container, false);    
}

@Override 
public void onViewCreated (View view, Bundle savedInstanceState) {
    listview = (ListView) view.findViewById(R.id.listview1);
    try 
    {
        // put your codes here
    } catch (Exception e) 
    {
        e.printStackTrace();
    }
}

Answer 4

Use onActivityCreated(Bundle savedInstanceState) overrided method and try placing your code in that. It will help to fix this crash.Because creating view before it exists produces this exception and crashes your application.using onPause() and onResume() whenever you move from this view reduces crash too.

Answer 5

Your problem is you have created your ListView on onCreateView() method, and you have set adapter in onCreate(). So onCreate() must be called before onCreateView(), that's why ListViews is not initialized, and you have found null pointer exception.