Android App Crashes on Startup: SQLite NullPointerException in ContactsFragment

Question

I'm working on integrating a database to save and store basic contact information to be retrieved at a later time. However, my app is now crashing on startup so I cannot even verify if the table is being created, etc.

05-05 16:39:50.671  11631-11631/treehouse.greenlight E/AndroidRuntime﹕   FATAL EXCEPTION: main
Process: treehouse.greenlight, PID: 11631
java.lang.RuntimeException: Unable to start activity ComponentInfo{treehouse.greenlight/treehouse.greenlight.Home_screen}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2205)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2255)
        at android.app.ActivityThread.access$800(ActivityThread.java:142)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1203)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5118)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:610)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference
        at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
        at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
        at treehouse.greenlight.MyDBHandler.addContact(MyDBHandler.java:54)
        at treehouse.greenlight.ContactsFragment.onCreateLoader(ContactsFragment.java:117)
        at android.support.v4.app.LoaderManagerImpl.createLoader(LoaderManager.java:490)
        at android.support.v4.app.LoaderManagerImpl.createAndInstallLoader(LoaderManager.java:499)
        at android.support.v4.app.LoaderManagerImpl.initLoader(LoaderManager.java:553)
        at treehouse.greenlight.ContactsFragment.onActivityCreated(ContactsFragment.java:71)
        at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:1797)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:979)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1138)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1120)
        at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1929)
        at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:547)
        at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
        at android.app.Activity.performStart(Activity.java:5285)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2178) 

Database Handler Code:

public class MyDBHandler extends SQLiteOpenHelper {

private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "contactsDB.db";
public static final String TABLE_CONTACTS = "contacts";
private Context context;
public static final String COLUMN_ID = "_id";
public static final String COLUMN_NAME = "name";
public static final String COLUMN_PHONE = "phone";
public static final String COLUMN_STATUS = "status";
public static final String COLUMN_BLURB = "blurb";

public MyDBHandler(Context context, String name,
                   CursorFactory factory, int version)  {
    super(context, DATABASE_NAME, factory, DATABASE_VERSION);

}
    @Override
    public void onCreate (SQLiteDatabase db){

        String CREATE_CONTACTS_TABLE = "CREATE TABLE " +
                TABLE_CONTACTS + "("
                + COLUMN_ID + " INTEGER PRIMARY KEY," + ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME
                + " TEXT," + ContactsContract.CommonDataKinds.Phone.NUMBER + " INTEGER,"
                + COLUMN_STATUS + " TEXT," + COLUMN_BLURB
                + " TEXT" + ");";
        db.execSQL(CREATE_CONTACTS_TABLE);
    }

    @Override
    public void onUpgrade (SQLiteDatabase db,int oldVersion, int newVersion){
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);
        onCreate(db);
    }
public void addContact(ContactsDb contacts) {

    ContentValues values = new ContentValues();
    values.put(COLUMN_NAME, contacts.getName());
    values.put(COLUMN_PHONE, contacts.getPhone());
    values.put(COLUMN_STATUS, contacts.getStatus());
    values.put(COLUMN_BLURB, contacts.getBlurb());

    SQLiteDatabase db = this.getWritableDatabase();
    db.insert(TABLE_CONTACTS, null, values);

}

The logcat says the issue is with SQLiteDatabase db = this.getWriteableDatabase();

Here is my offending Contactsfragment as well:

public class ContactsFragment extends ListFragment implements LoaderManager.LoaderCallbacks<Cursor> {

private CursorAdapter mAdapter;
private Context context;
TextView idView;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // create adapter once
    Context context = getActivity();
    int layout = R.layout.activity_list_item_1;
    Cursor c = null; // there is no cursor yet
    int flags = 0; // no auto-requery! Loader requeries.
    mAdapter = new SimpleCursorAdapter(context, layout, c, FROM, TO, flags);

}


public void ContactsDb(Context context) {
    this.context=context;


}
Uri contentUri = ContactsContract.CommonDataKinds.Phone.CONTENT_URI;

String[] PROJECTION = {
        ContactsContract.Contacts.HAS_PHONE_NUMBER,
        ContactsContract.Contacts._ID, // _ID is always required
        ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME_PRIMARY, // that is what we want to display
        Contacts.TIMES_CONTACTED,
        ContactsContract.CommonDataKinds.Phone.NUMBER

};

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    // each time we are started use our listadapter
    setListAdapter(mAdapter);
    // and tell loader manager to start loading
    getLoaderManager().initLoader(0, null, this);
}

// columns requested from the database


// and name should be displayed in the text1 textview in item layout

public String[] has_phone = {ContactsContract.Contacts.HAS_PHONE_NUMBER};

    String phone = "0";
    int dbPhone = 0;
private  final String[] FROM = {Contacts.DISPLAY_NAME_PRIMARY, ContactsContract.CommonDataKinds.Phone.NUMBER};
private final int[] TO = {android.R.id.text1, dbPhone};


public void newContact (View view) {
    MyDBHandler dbHandler = new MyDBHandler(context, null, null, 1);

    String name = Contacts.DISPLAY_NAME_PRIMARY;
    int dbPhone =
    Integer.parseInt(phone);

    String status ="";
    String blurb ="";
    ContactsDb contacts =
            new ContactsDb(name, dbPhone, status, blurb);
    dbHandler.addContact(contacts);

}


@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    Context context = this.context;
    // load from the "Contacts table"
    MyDBHandler dbHandler = new MyDBHandler(context, null, null, 1);

    String name = Contacts.DISPLAY_NAME_PRIMARY;
    int phone = Integer.parseInt(ContactsContract.CommonDataKinds.Phone.NUMBER);

    String status ="Busy";
    String blurb ="N/A";

    ContactsDb contacts =
            new ContactsDb(name, dbPhone, status, blurb);
    dbHandler.addContact(contacts);

    // no sub-selection, no sort order, simply every row
    // projection says we want just the _id and the name column
    return new CursorLoader(getActivity(),
            contentUri,
            PROJECTION,
            ContactsContract.Contacts.HAS_PHONE_NUMBER + " =? AND " + Contacts.TIMES_CONTACTED + ">=?", // This is selection string, we're looking for records that HAS_PHONE_NUMBER is 1
            new String[]{"1", "0"}, // 1 means that contact has a phone number & 60 is the amount of times contacted (arbitrary - needs to be fixed before release)
            null);
}

Finally, here is the ContactsDB class:

public ContactsDb(String name, int phone, String status, String blurb) {

    this._name = name;
    this._phone = phone;
    this._status = status;
    this._blurb = blurb;

Any help is much appreciated -- I think the issue lies with my Context being null. I'm just not sure why it would be as I've defined it in my MyDBHandler file. As of right now, I have no way of verifying that the db is being created, let alone holds data.

Cheers & Thanks for your time and patience, Shyam

Answer 1

It looks like you accidentally created a context local variable instead of using the instance variable.

So, context is null when you pass it into MyDBHandler, so when you call this.getWritableDatabase(), this is null. As a result, you get the NullPointerException, as you can see in the log:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference
        at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
        at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)

Try moving all of the Context related code to onActivityCreated() to ensure you have a valid Context, and make sure to use the instance variable instead of a local variable:

public class ContactsFragment extends ListFragment implements LoaderManager.LoaderCallbacks<Cursor> {

private CursorAdapter mAdapter;
private Context context; //this is the Context you will use
TextView idView;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // create adapter once
    //Context context = getActivity(); //Here was the problem
    //int layout = R.layout.activity_list_item_1;
    //Cursor c = null; // there is no cursor yet
    //int flags = 0; // no auto-requery! Loader requeries.
    //mAdapter = new SimpleCursorAdapter(context, layout, c, FROM, TO, flags);

}


public void ContactsDb(Context context) {
    this.context=context;


}
Uri contentUri = ContactsContract.CommonDataKinds.Phone.CONTENT_URI;

String[] PROJECTION = {
        ContactsContract.Contacts.HAS_PHONE_NUMBER,
        ContactsContract.Contacts._ID, // _ID is always required
        ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME_PRIMARY, // that is what we want to display
        Contacts.TIMES_CONTACTED,
        ContactsContract.CommonDataKinds.Phone.NUMBER

};

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    //Add this here:
    context = getActivity(); //use the instance variable
    int layout = R.layout.activity_list_item_1;
    Cursor c = null; // there is no cursor yet
    int flags = 0; // no auto-requery! Loader requeries.
    mAdapter = new SimpleCursorAdapter(context, layout, c, FROM, TO, flags);

    // each time we are started use our listadapter
    setListAdapter(mAdapter);
    // and tell loader manager to start loading
    getLoaderManager().initLoader(0, null, this);
}

// columns requested from the database


// and name should be displayed in the text1 textview in item layout

public String[] has_phone = {ContactsContract.Contacts.HAS_PHONE_NUMBER};

    String phone = "0";
    int dbPhone = 0;
private  final String[] FROM = {Contacts.DISPLAY_NAME_PRIMARY, ContactsContract.CommonDataKinds.Phone.NUMBER};
private final int[] TO = {android.R.id.text1, dbPhone};


public void newContact (View view) {

    //context should now be valid:
    MyDBHandler dbHandler = new MyDBHandler(context, null, null, 1);

    String name = Contacts.DISPLAY_NAME_PRIMARY;
    int dbPhone =
    Integer.parseInt(phone);

    String status ="";
    String blurb ="";
    ContactsDb contacts =
            new ContactsDb(name, dbPhone, status, blurb);
    dbHandler.addContact(contacts);

}
//........