ListView throws NullPointer Exception when multiple ListView in Fragment

Question

I am trying to implement Tab + Fragment and each of Fragment includes ListView which does background work as they take out the database values and show them.

I am managing those tabs using a FragmentActivity

public class MainActivity extends FragmentActivity implements
    ActionBar.TabListener {

SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final ActionBar actionBar = getActionBar();
    int color = Color.parseColor("#0101DF");
    actionBar.setBackgroundDrawable((new ColorDrawable(color)));
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
    mSectionsPagerAdapter = new SectionsPagerAdapter(
            getSupportFragmentManager());
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mSectionsPagerAdapter);
    mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
                @Override
                public void onPageSelected(int position) {
                    actionBar.setSelectedNavigationItem(position);
                }
            });

    for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
        actionBar.addTab(actionBar.newTab()
                .setText(mSectionsPagerAdapter.getPageTitle(i))
                .setTabListener(this));
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public void onTabSelected(ActionBar.Tab tab,
        FragmentTransaction fragmentTransaction) {
    mViewPager.setCurrentItem(tab.getPosition());
}

@Override
public void onTabUnselected(ActionBar.Tab tab,
        FragmentTransaction fragmentTransaction) {
}

@Override
public void onTabReselected(ActionBar.Tab tab,
        FragmentTransaction fragmentTransaction) {
}

/**
 * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
 * one of the sections/tabs/pages.
 */
public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a DummySectionFragment (defined as a static inner class
        // below) with the page number as its lone argument.
        Fragment fragment = null;
        if(position == 0)
        {
            Log.v("ONMESSAGE", "Position 0");
            fragment = new NewFragment();
            Bundle args = new Bundle();
            fragment.setArguments(args);
        }
        if(position == 1)
        {
            Log.v("ONMESSAGE", "Position 1");
            fragment = new CalledFragment();
            Bundle args = new Bundle();
            fragment.setArguments(args);
        }
        if(position == 2)
        {
            Log.v("ONMESSAGE", "Position 2");
            fragment = new SkippedFragment();
            Bundle args = new Bundle();
            fragment.setArguments(args);
        }

        return fragment;
    }

    @Override
    public int getCount() {
        // Show 3 total pages.
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        Locale l = Locale.getDefault();
        switch (position) {
        case 0:
            return "New";
        case 1:
            return "Called";
        case 2:
            return "Skipped";
        }
        return null;
    }
}


   }

I am giving example of one of those Fragment codes below .

public class CalledFragment extends Fragment{
View rootView;
ProgressDialog pDialog;
private ListView listView1;
CalledListAdapter adapter;
private static final String SAMPLE_DB_NAME = "androidData.sqlite";
private SQLiteDatabase sampleDB;
ArrayList<Person>list;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {  
    rootView = inflater.inflate(R.layout.calledfragment, container, false); 
    //list = new ArrayList<Person>();
    //new CallLogDetails().execute();
    return rootView;
}
 public ArrayList<Person> getList()
 {
     ArrayList<Person> arr = new ArrayList<Person>();
     sampleDB= getActivity().openOrCreateDatabase(SAMPLE_DB_NAME, Context.MODE_PRIVATE, null);
     Cursor cc = sampleDB.rawQuery("SELECT * FROM " +"calldetails", null);      
     if(cc != null)
    if(cc.moveToFirst()){
     do
     {  // Log.v("Datas",cc.getString(2)+ " " +cc.getString(3) + " " + cc.getString(1) + " " + cc.getInt(4));
         if(cc.getInt(4) == 2){
         Person ph = new Person(cc.getString(2), cc.getString(3), cc.getString(1),cc.getInt(4),cc.getInt(0));           
         arr.add(ph);
         }

     }while(cc.moveToNext());
    }
     sampleDB.close();
     Log.v("ONMESSAGE","Size at called" + arr.size());
     return arr;
 }
 private class CallLogDetails extends AsyncTask<Void,Void,Void>{

        @Override
         protected void onPreExecute(){
            pDialog = new ProgressDialog(getActivity());
            pDialog.setTitle("Processing");
            pDialog.setMessage("Loading Called List");
            pDialog.setIndeterminate(true);
            pDialog.setCancelable(false);
            pDialog.show();
         }

        protected void onPostExecute(Void params){
            super.onPostExecute(params);
            pDialog.dismiss();
            if(list.size() == 0)
         {
             list.add(new Person("No Data", "NO Data", "No Data", 0,0));
         }

         Collections.reverse(list);
         if(adapter != null)
         adapter.clear();
         adapter = new CalledListAdapter(getActivity(), R.layout.calledlist, list);
         listView1 = (ListView)getActivity().findViewById(R.id.calledlist);         
         listView1.setOnItemLongClickListener(new OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> arg0, View arg1, final int arg2, long arg3) {
                AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
                builder.setTitle("Delete Record");
                builder.setMessage("Do you want to delete the record?");
                builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {

                    @Override
                    public void onClick(DialogInterface arg0, int arg1) {
                        // TODO Auto-generated method stub
                        if(list.size() > 0){
                            sampleDB=getActivity().openOrCreateDatabase(SAMPLE_DB_NAME, SQLiteDatabase.OPEN_READWRITE, null);
                             //sampleDB.execSQL("DELETE FROM "+ SAMPLE_DB_NAME + " " + "WHERE callDesc= " + desc);
                            //sampleDB.execSQL("DELETE FROM calldetails WHERE callDesc='"+desc+"';"); 
                            Toast.makeText(getActivity(), "Row Deleted", Toast.LENGTH_LONG).show();
                             sampleDB.close();
                             new CallLogDetails().execute();
                        } else
                            Toast.makeText(getActivity(), "This is a default object. You can not delete this.", Toast.LENGTH_LONG).show();

                    }
                });
                builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {

                    @Override
                    public void onClick(DialogInterface arg0, int arg1) {
                        // TODO Auto-generated method stub
                        arg0.cancel();

                    }
                });
                builder.show();
                     return false;

    }
    });

         listView1.setAdapter(adapter);


        }
        @Override
        protected Void doInBackground(Void... arg0) {
            Log.v("ONMESSAGE", "Doing in background");
            list.clear();
            list = getList();
            return null;
        }

     }


   }

ArrayAdapter for this Fragment is below

public class CalledListAdapter extends ArrayAdapter<Person> {
    Context context;
    SQLiteDatabase sb;
    private static final String SAMPLE_DB_NAME = "androidData.sqlite";
    int layoutResourceId;   
    ArrayList<Person> data = new ArrayList<Person>();

    public CalledListAdapter(Context context, int layoutResourceId, ArrayList<Person> data) {
        super(context, layoutResourceId,data);
        this.layoutResourceId = layoutResourceId;
        this.context = context;
        this.data = data;
    }
    public void refresh(ArrayList<Person>list){         
        data = list;
        notifyDataSetChanged();
    } 
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
     Log.v("ONMESSAGE","call list adapter");
        convertView = null;
        View row = convertView;
        if(row == null && data.get(position).flag == 2){
            LayoutInflater inflater = ((Activity)context).getLayoutInflater();
            row = inflater.inflate(layoutResourceId, parent, false);               
            final WeatherHolder holder = new WeatherHolder();
            holder.phoneNumber = (TextView)row.findViewById(R.id.callednumber);
            holder.fname =  (TextView)row.findViewById(R.id.firstname);
            Person weather = data.get(position);
            holder.phoneNumber.setText(weather.number);
            holder.fname.setText(weather.fName);
            row.setTag(holder);
        }  
        return row;
    }

    static class WeatherHolder
    {
        TextView phoneNumber;
        TextView fname;

    }
 }

If there is one ListView in a Fragment and other two have no List then it works good however if I try to add ListView to other Fragment it gives me following error

Logcat

05-06 09:31:54.410: E/AndroidRuntime(12697): java.lang.NullPointerException
05-06 09:31:54.410: E/AndroidRuntime(12697):    at android.widget.ListView.measureScrapChild(ListView.java:1169)
05-06 09:31:54.410: E/AndroidRuntime(12697):    at android.widget.ListView.measureHeightOfChildren(ListView.java:1252)
05-06 09:31:54.410: E/AndroidRuntime(12697):    at android.widget.ListView.onMeasure(ListView.java:1161)
05-06 09:31:54.410: E/AndroidRuntime(12697):    at android.view.View.measure(View.java:12865)
05-06 09:31:54.410: E/AndroidRuntime(12697):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4712)
05-06 09:31:54.410: E/AndroidRuntime(12697):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
05-06 09:31:54.410: E/AndroidRuntime(12697):    at android.view.View.measure(View.java:12865)
05-06 09:31:54.410: E/AndroidRuntime(12697):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4712)
05-06 09:31:54.410: E/AndroidRuntime(12697):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
05-06 09:31:54.410: E/AndroidRuntime(12697):    at android.view.View.measure(View.java:12865)
  05-06 09:31:54.410: E/AndroidRuntime(12697):at  android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1451)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.view.View.measure(View.java:12865)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4712)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.view.View.measure(View.java:12865)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:822)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:563)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.view.View.measure(View.java:12865)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4712)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2242)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.view.View.measure(View.java:12865)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1240)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2628)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.os.Handler.dispatchMessage(Handler.java:99)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.os.Looper.loop(Looper.java:137)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at android.app.ActivityThread.main(ActivityThread.java:4517)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at java.lang.reflect.Method.invokeNative(Native Method)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at java.lang.reflect.Method.invoke(Method.java:511)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
  05-06 09:31:54.410: E/AndroidRuntime(12697):  at dalvik.system.NativeStart.main(Native Method)
  05-06 09:32:02.580: I/Process(12697): Sending signal. PID: 12697 SIG: 9

Padma Kumar · Accepted Answer · 2014-05-06 06:16:57Z

1

you need to call this in your onCreateView

listView1 = (ListView)rootView.findViewById(R.id.calledlist);

answered May 6, 2014 at 6:16

Padma Kumar

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5 Comments

Saty Over a year ago

Why can not I call this on my AsynTask?

Padma Kumar Over a year ago

Where you are calling the AsyncTask?

Saty Over a year ago

I am calling in Oncreateview of the fragment!

Padma Kumar Over a year ago

that is blocked and I can see that you are calling in onClick of alert dialog.

Saty Over a year ago

that is of no use of of now. If you will see the onCreateView, you will see the AsyncTask call. onClick of alert is a future task that I am not trying to use now.

subair_a · Accepted Answer · 2014-05-06 06:25:59Z

1

List view is part of the fragment , so you cannot read the reference by calling getActivity().findViewbyId()

Instead, you can get the rootview of the fragment by calling getView,

Here getView will return your rootView.

ListView lv = rootView.findViewById(R.id.myList)

getView will return null if you try to call before onCreateView,because this view is returned from this method.

answered May 6, 2014 at 6:25

subair_a

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Comments

laalto · Accepted Answer · 2014-05-06 06:32:21Z

1

There's a NPE measuring list view children i.e. the list rows as returned by adapter getView().

The getView() code is incorrect. It can return nulls. Make sure getView() always returns an actual view that is configured for the specified position in the dataset.

answered May 6, 2014 at 6:32

laalto

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3 Comments

Saty Over a year ago

Could you please guide me through to change the code?

laalto Over a year ago

Start by removing the if(row == null && data.get(position).flag == 2)

Saty Over a year ago

Yeah @laalto I just put a try catch block in getView and it starts giving results..I will do as you advised here however there is a doubt...I just saw two of my fragments called when the application starts and when I change tabs from first to second it does not refresh. Why?

Piyush · Accepted Answer · 2014-05-06 06:36:05Z

1

Move this

listView1 = (ListView)getActivity().findViewById(R.id.calledlist);

to onCreateView() method. Like,

listView1 = (ListView)rootView.findViewById(R.id.calledlist);

answered May 6, 2014 at 6:36

Piyush

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3 Comments

Saty Over a year ago

I dont know however it still crashing after I changed the code.... The same error log I am getting so unable to say which line in my code...

Saty Over a year ago

I just looked at it and found out that getItem of FragmentActivity is called twice when I start up the application as I logs for position 0 and position 1. Is it normal or is there any flaw in my code?

Saty Over a year ago

Thanks all for your replies I just followed this example from the link below to create the FragmentActivity which holds the tab widget and all my code started working. Big thanks to Piyush Gupta, laalto and subi and Padma Kumar for reminding me the basics.

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