getActivity returning null from fragment

Question

For school I am making an android app. For this app I have a fragment, which shows a gridview with just strings, from a database. For this I need a fragment. When I call getActivity(), it returns null. The onAttach method, as suggested here doesn't get called before the app crashes. How should I solve this?
weekFragmetn.xml:

package nl.siebeh.schoolmate;

import java.util.ArrayList;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.GridView;

public class weekFragment extends Fragment {
    dbLayer db;
    Context mContext;

    @Override
    public void onAttach(Activity activity) {
        mContext = getActivity();
        Log.i("Schoolmate","onAttach called");
        super.onAttach(activity);
    }

    public weekFragment newInstance(String title) {
        Log.i("Schoolmate","newInstance called");
        db = new dbLayer(mContext);
        weekFragment fragment = new weekFragment();
        ArrayList<ArrayList<Object>> result = null;

        if(title == "leraren"){
            result = db.getAllRowsAsArrays("weekTeacher", null);
        }else if(title == "locatie"){
            result = db.getAllRowsAsArrays("weekLocation", null);
        }else if(title == "vakken"){
            result = db.getAllRowsAsArrays("weekSubjects", null);
        }

        String[] array = new String[60];

        for(int i = 0; i < 60; i++){
            array[i] = "";
        }

        array[1] = getResources().getStringArray(R.array.days)[0];
        array[2] = getResources().getStringArray(R.array.days)[1];
        array[3] = getResources().getStringArray(R.array.days)[2];
        array[4] = getResources().getStringArray(R.array.days)[3];
        array[5] = getResources().getStringArray(R.array.days)[4];

        for(int i = 1; i < 10; i++){
            array[i] = Integer.toString(i);
        }

        for(int position = 0; position < result.size(); position++){
            ArrayList<Object> row = result.get(position);
            int hour = Integer.valueOf(row.get(1).toString()).intValue();
            int day =  Integer.valueOf(row.get(0).toString()).intValue();
            int pos = 6 * hour + day;
            array[pos] = row.get(position).toString();
        }
        fragment.mContent = array;

        return fragment;
    }

    private String[] mContent = {""};

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        if (container == null) {
            return null;
        }
        View v = inflater.inflate(R.layout.week_fragment, container, false);
        GridView gridview = (GridView) v.findViewById(R.id.gridview);
        gridview.setAdapter(new weekAdapter(mContext, mContent));
        return gridview;
    }

    @Override
    public boolean onContextItemSelected(MenuItem item) {
        return super.onContextItemSelected(item);
    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);
    }



}

logcat: (since click on the item the item in a list that starts the activity, where the fragment is started/embedded)

    09-29 19:10:56.611: INFO/ActivityManager(70): Starting: Intent { cmp=nl.siebeh.schoolmate/.overviewWeek } from pid 536
09-29 19:10:56.970: INFO/Schoolmate(536): newInstance called
09-29 19:11:06.631: WARN/ActivityManager(70): Launch timeout has expired, giving up wake lock!
09-29 19:11:06.671: WARN/ActivityManager(70): Activity idle timeout for HistoryRecord{40770188 nl.siebeh.schoolmate/.overviewWeek}
09-29 19:12:20.661: DEBUG/SntpClient(70): request time failed: java.net.SocketException: Address family not supported by protocol
09-29 19:14:11.811: DEBUG/dalvikvm(536): Debugger has detached; object registry had 413 entries
09-29 19:14:11.811: ERROR/SchoolMate(536): java.lang.NullPointerException
09-29 19:14:11.811: INFO/SchoolMate(536): Context is null
09-29 19:14:11.820: WARN/System.err(536): java.lang.NullPointerException
09-29 19:14:11.820: WARN/System.err(536):     at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:118)
09-29 19:14:11.820: WARN/System.err(536):     at nl.siebeh.schoolmate.dbLayer.<init>(dbLayer.java:50)
09-29 19:14:11.820: WARN/System.err(536):     at nl.siebeh.schoolmate.weekFragment.newInstance(weekFragment.java:31)
09-29 19:14:11.820: WARN/System.err(536):     at nl.siebeh.schoolmate.fragmentAdapter.getItem(fragmentAdaptar.java:21)
09-29 19:14:11.820: WARN/System.err(536):     at nl.siebeh.schoolmate.titleFragmentAdapter.getItem(titleFragmentAdapter.java:1)
09-29 19:14:11.820: WARN/System.err(536):     at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:62)
09-29 19:14:11.820: WARN/System.err(536):     at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:321)
09-29 19:14:11.820: WARN/System.err(536):     at android.support.v4.view.ViewPager.populate(ViewPager.java:441)
09-29 19:14:11.820: WARN/System.err(536):     at android.support.v4.view.ViewPager.onAttachedToWindow(ViewPager.java:563)
09-29 19:14:11.820: WARN/System.err(536):     at android.view.View.dispatchAttachedToWindow(View.java:6156)
09-29 19:14:11.820: WARN/System.err(536):     at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:1122)
09-29 19:14:11.820: WARN/System.err(536):     at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:1127)
09-29 19:14:11.820: WARN/System.err(536):     at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:1127)
09-29 19:14:11.820: WARN/System.err(536):     at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:1127)
09-29 19:14:11.820: WARN/System.err(536):     at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:1127)
09-29 19:14:11.820: WARN/System.err(536):     at android.view.ViewRoot.performTraversals(ViewRoot.java:765)
09-29 19:14:11.830: WARN/System.err(536):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
09-29 19:14:11.840: WARN/System.err(536):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-29 19:14:11.840: WARN/System.err(536):     at android.os.Looper.loop(Looper.java:123)
09-29 19:14:11.840: WARN/System.err(536):     at android.app.ActivityThread.main(ActivityThread.java:3683)
09-29 19:14:11.840: WARN/System.err(536):     at java.lang.reflect.Method.invokeNative(Native Method)
09-29 19:14:11.840: WARN/System.err(536):     at java.lang.reflect.Method.invoke(Method.java:507)
09-29 19:14:11.850: WARN/System.err(536):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
09-29 19:14:11.850: WARN/System.err(536):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
09-29 19:14:11.850: WARN/System.err(536):     at dalvik.system.NativeStart.main(Native Method)
09-29 19:14:11.850: DEBUG/AndroidRuntime(536): Shutting down VM
09-29 19:14:11.850: WARN/dalvikvm(536): threadid=1: thread exiting with uncaught exception (group=0x40015560)
09-29 19:14:11.870: ERROR/AndroidRuntime(536): FATAL EXCEPTION: main
09-29 19:14:11.870: ERROR/AndroidRuntime(536): java.lang.NullPointerException
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at nl.siebeh.schoolmate.weekFragment.newInstance(weekFragment.java:49)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at nl.siebeh.schoolmate.fragmentAdapter.getItem(fragmentAdaptar.java:21)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at nl.siebeh.schoolmate.titleFragmentAdapter.getItem(titleFragmentAdapter.java:1)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:62)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:321)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.support.v4.view.ViewPager.populate(ViewPager.java:441)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.support.v4.view.ViewPager.onAttachedToWindow(ViewPager.java:563)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.view.View.dispatchAttachedToWindow(View.java:6156)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:1122)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:1127)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:1127)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:1127)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:1127)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.view.ViewRoot.performTraversals(ViewRoot.java:765)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.os.Looper.loop(Looper.java:123)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at android.app.ActivityThread.main(ActivityThread.java:3683)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at java.lang.reflect.Method.invokeNative(Native Method)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at java.lang.reflect.Method.invoke(Method.java:507)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
09-29 19:14:11.870: ERROR/AndroidRuntime(536):     at dalvik.system.NativeStart.main(Native Method)
09-29 19:14:11.890: WARN/ActivityManager(70):   Force finishing activity nl.siebeh.schoolmate/.overviewWeek
09-29 19:14:12.413: WARN/ActivityManager(70): Activity pause timeout for HistoryRecord{40770188 nl.siebeh.schoolmate/.overviewWeek}
09-29 19:14:21.910: WARN/ActivityManager(70): Launch timeout has expired, giving up wake lock!
09-29 19:14:22.441: WARN/ActivityManager(70): Activity idle timeout for HistoryRecord{4070c7a0 nl.siebeh.schoolmate/.schoolmate}
09-29 19:14:32.451: WARN/ActivityManager(70): Activity destroy timeout for HistoryRecord{40770188 nl.siebeh.schoolmate/.overviewWeek}

score 8 · Accepted Answer · answered Sep 29 '11 at 20:27

8

You do not have a getActivity() call, which makes it difficult to answer the question.

You are getting a NullPointerException because mContext is null. My guess is that mContext is null because, in the code to fragmentAdapter, you are calling new weekFragment(), then calling newInstance() on it. You presumably thought you were following some patterns outlined in the Fragment JavaDocs, but in there, newInstance() is a static method, not an instance method as you have it here.

Take just about all of the code out of newInstance() and move it to onActivityCreated() or some time when the fragment is attached to the activity so getActivity() works. Along the way, delete your onAttach() implementation and the mContext data member, neither of which are needed (and the mContext is populated in a very scary way).

answered Sep 29 '11 at 20:27

CommonsWare

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Thanks for the quick response. In onAttach should the mContext be set to getActivity(), What it is now is something I found on another site. I will try it out immediately. – Siebe Sep 29 '11 at 20:58
@Swilzard: "In onAttach should the mContext be set to getActivity()" -- no, just call `getActivity()` when you need the `Activity`. – CommonsWare Sep 29 '11 at 21:09
@CommonsWare : in my case I am launching fragment on click of button..so here it's assumed activity already created. but now here if call getActivity().finish() from fragment..it's giving NULL POINTER...any suggestion.? – CoDe Jan 22 '13 at 11:14
@Shubh: My suggestion would be to open a fresh StackOverflow question. – CommonsWare Jan 22 '13 at 12:28

getActivity returning null from fragment

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