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PONullPointerException when calling a database
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  1. PONullPointerException when calling a database
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    copied!<p>As the title says I get a NullPointerException when I try to get a list from a database. Here is the code: </p> <pre><code>public List&lt;String&gt; getAllRockBands() { List&lt;String&gt; bandList = new ArrayList&lt;String&gt;(); String selection = BAND_GENRE + "=1"; SQLiteDatabase db = sqLiteHelper.getReadableDatabase(); Cursor cursor = db.query(BANDDATABASE_TABLE,new String[]{BAND_NAME}, selection, null, null, null, BAND_NAME); int index = cursor.getColumnIndex(BAND_NAME); if (cursor.moveToFirst()) { do { String bandName = cursor.getString(index); bandList.add(bandName); } while (cursor.moveToNext()); } return bandList; } </code></pre> <p>` </p> <pre><code>public class RockAllFragment extends SherlockListFragment { private BandDatabaseAdapter mySQLiteAdapter; private List&lt;String&gt; bandList = mySQLiteAdapter.getAllRockBands(); @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { return inflater.inflate(R.layout.my_list, null); } @Override public void onViewCreated(View view, Bundle savedInstanceState) { // TODO Auto-generated method stub super.onViewCreated(view, savedInstanceState); setListAdapter(new ArrayAdapter&lt;String&gt;(getSherlockActivity(), android.R.layout.simple_list_item_multiple_choice, android.R.id.text1, bandList)); } } </code></pre> <p>I am still learning to code in this environment, so I guess this is just some beginner mistake?</p> <p><strong>EDIT:</strong> (it's a bit much but you asked) </p> <pre><code>public class BandDatabaseAdapter { private static final String TAG = "BandDatabase"; private static final String BANDDATABASE_NAME = "BAND_DATABASE"; private static final String BANDDATABASE_TABLE = "BAND_TABLE"; private static final int BANDDATABASE_VERSION = 1; public static final String BAND_NAME = "name"; public static final String BAND_GENRE = "genre"; public static final String BAND_POPULAR = "popular"; public static final String BAND_SELECTED = "selected"; private static final String BANDDATABASE_CREATE="CREATE TABLE IF NOT EXISTS " + BANDDATABASE_TABLE + " (_id integer primary key autoincrement, " + BAND_NAME + " TEXT NOT NULL, " + BAND_GENRE + " TEXT NOT NULL, " + BAND_POPULAR + " TEXT NOT NULL, " + BAND_SELECTED + " TEXT NOT NULL)"; private SQLiteHelper sqLiteHelper; private SQLiteDatabase sqLiteDatabase; private final Context context; public BandDatabaseAdapter(Context c) { sqLiteHelper = new SQLiteHelper(c, BANDDATABASE_NAME, null, BANDDATABASE_VERSION); context = c; } public BandDatabaseAdapter openToRead() throws android.database.SQLException { sqLiteDatabase = sqLiteHelper.getReadableDatabase(); return this; } public BandDatabaseAdapter openToWrite() throws android.database.SQLException { sqLiteDatabase = sqLiteHelper.getWritableDatabase(); return this; } public void close(){ sqLiteHelper.close(); } public void updateBand(String name, String selected) { ContentValues contentValues = new ContentValues(); contentValues.put(BAND_SELECTED, selected); sqLiteDatabase.update(BANDDATABASE_TABLE, contentValues, "BAND_NAME=" + name, null); close(); } public List&lt;String&gt; getAllRockBands() { List&lt;String&gt; bandList = new ArrayList&lt;String&gt;(); String selection = BAND_GENRE + "=1"; SQLiteDatabase db = sqLiteHelper.getReadableDatabase(); Cursor cursor = db.query(BANDDATABASE_TABLE,new String[]{BAND_NAME}, selection, null, null, null, BAND_NAME); if(cursor!=null) { int index = cursor.getColumnIndex(BAND_NAME); if (cursor.moveToFirst()) { do { String bandName = cursor.getString(index); bandList.add(bandName); } while (cursor.moveToNext()); } } return bandList; } public List&lt;String&gt; getMyList() { List&lt;String&gt; myList = new ArrayList&lt;String&gt;(); String selection = BAND_SELECTED + "=1"; SQLiteDatabase db = sqLiteHelper.getReadableDatabase(); Cursor cursor = db.query(BANDDATABASE_TABLE,new String[]{BAND_NAME}, selection, null, null, null, BAND_NAME); int index = cursor.getColumnIndex(BAND_NAME); if (cursor.moveToFirst()) { do { String bandName = cursor.getString(index); myList.add(bandName); } while (cursor.moveToNext()); } return myList; } public class SQLiteHelper extends SQLiteOpenHelper { public SQLiteHelper(Context context, String name, CursorFactory factory, int version) { super(context, name, factory, version); } private boolean doesDatabaseExist(Context context, String dbName) { File dbFile=context.getDatabasePath(dbName); return dbFile.exists(); } @Override public void onCreate(SQLiteDatabase db) { // TODO Auto-generated method stub if(!(doesDatabaseExist(context,BANDDATABASE_NAME))) { db.execSQL(BANDDATABASE_CREATE); loadDatabase(); } } /** * Starts a thread to load the database table with bands */ private void loadDatabase() { new Thread(new Runnable() { public void run() { try { loadBands(); } catch (IOException e) { throw new RuntimeException(e); } } }).start(); } //loads a database from a txt file private void loadBands() throws IOException { Log.d(TAG, "Loading bands..."); final Resources resources = context.getResources(); InputStream inputStream = resources.openRawResource(R.raw.bands); BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream)); try { String line; while ((line = reader.readLine()) != null) { String[] strings = TextUtils.split(line, "^"); if (strings.length &lt; 4) continue; long id = addBand(strings[0].trim(), strings[1].trim(), strings[2].trim()); if (id &lt; 0) { Log.e(TAG, "unable to add band: " + strings[0].trim()); } } } finally { reader.close(); } Log.d(TAG, "DONE loading words."); } public long addBand(String name, String genre, String popular) { ContentValues initialValues = new ContentValues(); initialValues.put(BAND_NAME, name); initialValues.put(BAND_GENRE, genre); initialValues.put(BAND_POPULAR, popular); initialValues.put(BAND_SELECTED, "0"); return sqLiteDatabase.insert(BANDDATABASE_TABLE, null, initialValues); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub // Drop older table if existed db.execSQL("DROP TABLE IF EXISTS " + BANDDATABASE_TABLE); // Create tables again onCreate(db); } } } </code></pre> <p>Additional info: Some people have told me to use SimpleCursorAdapter, but it says it is deprecated. Also, note that my list has over 150k rows, tho I will greatly lessen that if the need arises. :)</p>
 

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