java.lang.NullPointerException, FATAL EXCEPTION at listview

Question

Hi I'm new to android and pardon me as it is my first time developing a mobile application for my school assignment. I have an error which made my app crashed whenever I try to start the app and my guess is that the retrieving is the culprit.

I am creating an activity that is supposed to display an empty list which will allow the user the input of CRUD. I do understand that the error is due to null but how do I make it so that it allows the display of an empty list? I would appreciate any help on how to go about this, thank you!

Here is the logcat:

02-11 18:41:53.803: W/dalvikvm(18334): threadid=1: thread exiting with    uncaught exception (group=0x41763da0)
02-11 18:41:53.803: E/AndroidRuntime(18334): FATAL EXCEPTION: main
02-11 18:41:53.803: E/AndroidRuntime(18334): Process: com.example.sgrecipe, PID: 18334
02-11 18:41:53.803: E/AndroidRuntime(18334): java.lang.NullPointerException
02-11 18:41:53.803: E/AndroidRuntime(18334):    at com.example.sgrecipe.FavouriteFragment.fetchData(FavouriteFragment.java:174)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at  com.example.sgrecipe.FavouriteFragment.initControls(FavouriteFragment.java:92)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at com.example.sgrecipe.FavouriteFragment.onStart(FavouriteFragment.java:50)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.support.v4.app.Fragment.performStart(Fragment.java:1484)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:941)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.support.v4.app.FragmentManagerImpl.performPendingDeferredStart(FragmentManager.java:807)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.support.v4.app.FragmentManagerImpl.startPendingDeferredFragments(FragmentManager.java:1112)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1461)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:461)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.support.v4.view.ViewPager.populate(ViewPager.java:1064)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.support.v4.view.ViewPager.populate(ViewPager.java:911)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1432)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.View.measure(View.java:17396)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5365)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.View.measure(View.java:17396)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5365)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:382)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.View.measure(View.java:17396)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5365)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2505)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.View.measure(View.java:17396)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2175)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1316)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1513)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1200)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6401)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:803)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.Choreographer.doCallbacks(Choreographer.java:603)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.Choreographer.doFrame(Choreographer.java:573)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:789)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.os.Handler.handleCallback(Handler.java:733)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.os.Handler.dispatchMessage(Handler.java:95)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.os.Looper.loop(Looper.java:157)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at android.app.ActivityThread.main(ActivityThread.java:5335)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at java.lang.reflect.Method.invokeNative(Native Method)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at java.lang.reflect.Method.invoke(Method.java:515)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
02-11 18:41:53.803: E/AndroidRuntime(18334):    at dalvik.system.NativeStart.main(Native Method)

FavouriteFragment.java:

package com.example.sgrecipe;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.Toast;

 public class FavouriteFragment extends Fragment implements OnClickListener{

// Primitive Variables
String selected_ID = "";

// Widget GUI Declare
EditText txtTitle, txtDesc, txtSalary;
Button btnAdd, btnUpdate, btnDelete;
ListView lvNotes;

// DB Objects
DBHelper helper;
SQLiteDatabase db;

// Adapter Object
SimpleCursorAdapter adapter;

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

    View rootView = inflater.inflate(R.layout.activity_favourite_fragment, container, false);

    return rootView;

}

  @Override
   public void onStart() {
   super.onStart();
   initControls();
   // Init DB Objects
   helper = new DBHelper(getActivity());}

   // Widget GUI Init
   private void initControls(){
   txtTitle = (EditText)getView().findViewById(R.id.txtTitle);
   txtDesc = (EditText)getView().findViewById(R.id.txtDes);
   txtSalary = (EditText)getView().findViewById(R.id.txtSalary);
   lvNotes = (ListView)getView().findViewById(R.id.lvNotes);

   btnAdd = (Button)getView().findViewById(R.id.btnAdd);
   btnUpdate = (Button)getView().findViewById(R.id.btnUpdate);
   btnDelete = (Button)getView().findViewById(R.id.btnDelete);

   // Attached Listener
   btnAdd.setOnClickListener(this);
   btnUpdate.setOnClickListener(this);
   btnDelete.setOnClickListener(this);
   lvNotes.setOnItemClickListener(new OnItemClickListener() {

       @Override
       public void onItemClick(AdapterView<?> adapter, View v,
               int position, long id) {

           String title, desc, salary;

           // Display Selected Row of Listview into EditText widget

           Cursor row = (Cursor) adapter.getItemAtPosition(position);
           selected_ID = row.getString(0);
           title = row.getString(1);
           desc = row.getString(2);
           salary = row.getString(3);

           txtTitle.setText(title);
           txtDesc.setText(desc);
           txtSalary.setText(salary);
       }
   });

   // Fetch Data from database
   fetchData();
 }


@Override
public void onClick(View v) {

    // Perform CRUD Operation

    if (v == btnAdd) {

        // Add Record with help of ContentValues and DBHelper class object
        ContentValues values = new ContentValues();
        values.put(DBHelper.C_TITLE, txtTitle.getText().toString());
        values.put(DBHelper.C_DESCRIPTION, txtDesc.getText().toString());
        values.put(DBHelper.C_SALARY, txtSalary.getText().toString());

        // Call insert method of SQLiteDatabase Class and close after
        // performing task
        db = helper.getWritableDatabase();
        db.insert(DBHelper.TABLE, null, values);
        db.close();

        clearFields();
        Toast.makeText(this.getActivity(), "Successfully Added",
                Toast.LENGTH_LONG).show();

        // Fetch Data from database and display into listview
        fetchData();

    }
    if (v == btnUpdate) {

        // Update Record with help of ContentValues and DBHelper class
        // object

        ContentValues values = new ContentValues();
        values.put(DBHelper.C_TITLE, txtTitle.getText().toString());
        values.put(DBHelper.C_DESCRIPTION, txtDesc.getText().toString());
        values.put(DBHelper.C_SALARY, txtSalary.getText().toString());

        // Call update method of SQLiteDatabase Class and close after
        // performing task
        db = helper.getWritableDatabase();
        db.update(DBHelper.TABLE, values, DBHelper.C_ID + "=?",
                new String[] { selected_ID });
        db.close();

        // Fetch Data from database and display into listview
        fetchData();
        Toast.makeText(this.getActivity(), "Record Updated Successfully",
                Toast.LENGTH_LONG).show();
        clearFields();

    }
    if (v == btnDelete) {

        // Call delete method of SQLiteDatabase Class to delete record and
        // close after performing task
        db = helper.getWritableDatabase();
        db.delete(DBHelper.TABLE, DBHelper.C_ID + "=?",
                new String[] { selected_ID });
        db.close();

        // Fetch Data from database and display into listview
        fetchData();
        Toast.makeText(this.getActivity(), "Record Deleted Successfully",
                Toast.LENGTH_LONG).show();
        clearFields();

    }
}

 // Clear Fields
    private void clearFields() {
        txtTitle.setText("");
        txtDesc.setText("");
        txtSalary.setText("");
    }

 // Fetch Fresh data from database and display into listview
    private void fetchData() {
        db = helper.getReadableDatabase();
        Cursor c = db.query(DBHelper.TABLE, null, null, null, null, null, null);
        adapter = new SimpleCursorAdapter(
                getActivity(),
                R.layout.row,
                c,
                new String[] { DBHelper.C_TITLE, DBHelper.C_SALARY,
                        DBHelper.C_DESCRIPTION },
                new int[] { R.id.lblTitle, R.id.lblSalary, R.id.lblDescription });
        lvNotes.setAdapter(adapter);
    }
    }

activity_favourite_fragment.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:focusable="true"
android:focusableInTouchMode="true"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:text="Notes"
    android:textAppearance="?android:attr/textAppearanceLarge" >
</TextView>

<EditText
    android:id="@+id/txtTitle"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:hint="Title" >

    <requestFocus>
    </requestFocus>
</EditText>

<EditText
    android:id="@+id/txtDes"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:hint="Description" >
</EditText>

<EditText
    android:id="@+id/txtSalary"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:hint="Enter Salary" >
</EditText>

<LinearLayout
    android:id="@+id/linearLayout1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >

    <Button
        android:id="@+id/btnAdd"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add" >
    </Button>

    <Button
        android:id="@+id/btnUpdate"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Update Record" >
    </Button>

    <Button
        android:id="@+id/btnDelete"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Delete" >
    </Button>
</LinearLayout>

<ListView
    android:id="@+id/lvNotes"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
</ListView>

I am just starting off with android development, any help would be appreciated!

Gil Moshayof · Accepted Answer · 2015-02-11 11:26:01Z

3

Your problem is in the onStart method:

public void onStart() 
 {
   super.onStart();
   initControls();
   // Init DB Objects
   helper = new DBHelper(getActivity());
 }

Notice that you're creating your helper object AFTER calling initControls(), which then calls fetchData().

In fetchData you have this line:

db = helper.getWritableDatabase();

This is the line that causes the null pointer exception because helper is null.

Change your onStart method like so:

 public void onStart() 
         {
           super.onStart();
           // Init DB Objects
           helper = new DBHelper(getActivity());
           initControls();

         }

This should solve your problem.

answered Feb 11, 2015 at 11:26

Gil Moshayof

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Comments

laalto · Accepted Answer · 2015-02-11 11:25:16Z

3

helper is not initialized.

In your onStart() you're only initializing it after calling initControls() which calls fetchData() that uses helper. Move the helper initialization before the initControls() call.

answered Feb 11, 2015 at 11:25

laalto

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Comments

Xcihnegn · Accepted Answer · 2015-02-11 11:35:21Z

0

Better solution, move code line:

helper = new DBHelper(getActivity());

from onStart() to onCreate() where is right place to initiate object

edited Feb 11, 2015 at 11:35

answered Feb 11, 2015 at 11:28

Xcihnegn

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1 Comment

Xcihnegn Over a year ago

onStart() will be called each time from invisible(background) to visible(foreground), but onCreate() just call once, so where you think should initiate your helper?

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