Question

I have a DatabaseHelper class and DatabaseAdapter class. When i try to select data from several activities, i get empty database. What am i doing wrong? I am reading or writing to dabase while calling database adapter and passing current activity as context.

public class DatabaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "MySampleDatabase";
    private static final int DATABASE_VERSION = 15;
    private final Context context;

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.context = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        AssetManager manager = context.getResources().getAssets();
        InputStream is;
        try {
            is = manager.open("SQLStatements");
            BufferedReader reader = new BufferedReader(new InputStreamReader(is));
            StringBuffer sb = new StringBuffer();
            String line;
            while((line = reader.readLine()) != null){
                sb.append(line);
            }
            String[] queries = (new String(sb)).split(";");
            is.close();
            for(int i = 0; i < queries.length; i++){
                db.execSQL(queries[i]);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS UserDrugs");
        db.execSQL("DROP TABLE IF EXISTS UserDrugsUsages");
        onCreate(db);
    }
}
public class DatabaseUserDrugsUsagesAdapter {
    public static final String KEY_USER_DRUG_ID = "UserDrugID";
    public static final String KEY_PACKAGE_ID = "PackageID";
    public static final String KEY_TIME_TO_USE = "TimeToUse";
    public static final String KEY_USED = "Used";
    public static final String KEY_PACKAGE_NAME = "PackageName";
    private static final String DATABASE_TABLE = "UserDrugsUsages";
    private Context context;
    private SQLiteDatabase database;
    private DatabaseHelper dbHelper;

    public DatabaseUserDrugsUsagesAdapter(Context context) {
        this.context = context;
    }

    public DatabaseUserDrugsUsagesAdapter open() throws SQLException {
        dbHelper = new DatabaseHelper(context);
        database = dbHelper.getWritableDatabase();
        return this;
    }

    public void close() {
        dbHelper.close();
    }

    public void clearDatabaseTable(){
        database.execSQL("DELETE FROM " + DATABASE_TABLE);
    }

    public Cursor selectUserDrugUsagesByDate(String date){
        return database.query(DATABASE_TABLE, new String[] {
                KEY_USER_DRUG_ID,
                KEY_PACKAGE_ID,
                KEY_TIME_TO_USE,
                KEY_USED,
                KEY_PACKAGE_NAME}, "TimeToUse like '" + date + "%'", null, null, null, null);
    }

    public long writeUserDrugUsage(int userDrugId, int packageId, String timeToUse, boolean used, String packageName) {
        ContentValues initialValues = createContentValues(userDrugId, packageId, timeToUse, used, packageName);

        return database.insert(DATABASE_TABLE, null, initialValues);
    }

    private ContentValues createContentValues(int userDrugId, int packageId, String timeToUse, boolean used, 
            String packageName) {

        ContentValues values = new ContentValues();
        values.put(KEY_USER_DRUG_ID, userDrugId);
        values.put(KEY_PACKAGE_ID, packageId);
        values.put(KEY_TIME_TO_USE, timeToUse);
        values.put(KEY_USED, used);
        values.put(KEY_PACKAGE_NAME, packageName);

        return values;
    }
}

EDIT:
There is the code where i call select function.

Cursor c = null;
String name = null;
DatabaseUserDrugsUsagesAdapter db = new DatabaseUserDrugsUsagesAdapter(context);
db.open();
c = db.selectDrugNameById(id);
db.close();

if(c != null && c.getCount() > 0){
    c.moveToFirst();
    name = c.getString(4);
}
c.close();

Answer 1

This is because you are you closed your database before manipulating the cursor.

Actually Cursor is like a list/pointer created from a database resource.

I changed your code and it will work just fine give it a try

Cursor c = null;
String name = null;
DatabaseUserDrugsUsagesAdapter db = new DatabaseUserDrugsUsagesAdapter(context);
db.open();
c = db.selectDrugNameById(id);

if(c != null && c.getCount() > 0){
     c.moveToFirst();
     name = c.getString(4);
        }
    c.close();
    db.close();