Question

i am creating an app that needs a database. i created it using sqlite database browser, which means the app i created, imports the database i created into the phone.

and what i’ve learnt before, is if i did any changes to the database using the browser, i have to uninstall the app from my phone/emulator so that it make the changes.

so the problem came. what happen if after i upload the app to the market, and realized that i need to update the table ??? and also, another problem is that user have to enter some data and save it into a table of the database.

so is there a way to update my database & yet keep the data that the user entered in the table ???

my database helper code is below. pls help…thanks alot !

public class DatabaseHelper extends SQLiteOpenHelper {

//The Android's default system path of your application database.
private static String DB_PATH = "/data/data/test.test/databases/";

private static String DB_NAME = "TestDatabase";

private static final int DB_VERSION = 1;

private SQLiteDatabase myDatabase; 

private final Context myContext;

/**
 *  # Constructor #
 * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
 * @param context
 */
public DatabaseHelper(Context context) {

    super(context, DB_NAME, null, DB_VERSION);
    this.myContext = context;
}//constructor  

/**
 *  # Create Database #
 * Creates a empty database on the system and rewrites it with your own database.
 */
public void createDatabase() throws IOException {

    boolean dbExist = checkDatabase();

    if(dbExist)
    {
        //do nothing - database already exist
    }//if

    else
    {
        //By calling this method and empty database will be created into the default system path
           //of your application so we are gonna be able to overwrite that database with our database.
        this.getReadableDatabase();

        try 
        {
            copyDatabase();

        } catch (IOException e) {

            throw new Error("Error copying database");

        }//catch
    }//else

}//createDatabase

private boolean checkDatabase() {

    SQLiteDatabase checkDB = null;

    try
    {
        String myPath = DB_PATH + DB_NAME;
        checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

    } catch(SQLiteException e) {

        //database does't exist yet.

    }//catch

    if(checkDB != null) 
    { 
        checkDB.close();

    }//if

    return checkDB != null ? true : false;

}//checkDatabase


private void copyDatabase() throws IOException {

    //Open your local db as the input stream
    InputStream myInput = myContext.getAssets().open(DB_NAME);

    // Path to the just created empty db
    String outFileName = DB_PATH + DB_NAME;

    //Open the empty db as the output stream
    OutputStream myOutput = new FileOutputStream(outFileName);

    //transfer bytes from the inputfile to the outputfile
    byte[] buffer = new byte[1024];
    int length;

    while ((length = myInput.read(buffer))>0)
    {
        myOutput.write(buffer, 0, length);
    }

    //Close the streams
    myOutput.flush();
    myOutput.close();
    myInput.close();

}//copyDatabase

// # open database #
public void openDatabase() throws SQLException {

    //Open the database
    String myPath = DB_PATH + DB_NAME;
    myDatabase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);

}//openDatabase

@Override
public synchronized void close() 
{
    if(myDatabase != null)
        myDatabase.close();

    super.close();

}//close

@Override
public void onCreate(SQLiteDatabase db) {

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

public List<String> selectData
    (String tableName, String [] columns, String selection, String[] selectionArgs,
            String groupBy, String having, String orderBy) {

    List<String> list = new ArrayList<String>();

    Cursor cursor = this.myDatabase.query(tableName, columns, selection, selectionArgs, groupBy, having, orderBy);

    if (cursor.moveToFirst()) 
    {
        do 
        {
            list.add(cursor.getString(0));
        }

        while (cursor.moveToNext());
    }

    if (cursor != null && !cursor.isClosed()) 
    {
        cursor.close();
    }
    return list;

}//selectData

public void insertData (String tableName, String nullColumnHack, ContentValues values) {

    try
    {
        myDatabase.insert(tableName, nullColumnHack, values);
    } catch (Exception e) {
        Log.e("Error :","unable to insert data");
    }//catch

}//insertData

//edit row
public void updateData (String tableName, ContentValues values, String whereClause, String[] whereArgs) {

    try
    {
        myDatabase.update(tableName, values, whereClause, whereArgs);
    } catch (Exception e) {
        Log.e("Error :","unable to update data");
    }//catch
}//updateData

public void deleteRow (String tableName, String whereClause, String[] whereArgs) {

    try
    {
        myDatabase.delete(tableName, whereClause, whereArgs);
    } catch (Exception e) {
        Log.e("Error :","unable to delete row");
    }//catch
}//deleteRow
}

Answer 1

That’s what:

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

is for.

Documentation here.