What is a Full Android Database Helper class for a

Question

I'm trying to deploy an application with an existing SQLite database.

I've read through and attempted to implement several samples online however I've found that they are always missing some code and either do not compile or work as advertised.

Does anyone have a Full Android Database Helper class for deploying an existing SQLite database on Android?

Answer 1

This is what I came up with, hope it helps others that were having troubles.

package com.MyPackage;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.UUID;

import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class AnyDBAdapter {

    private static final String TAG = "AnyDBAdapter";
    private DatabaseHelper mDbHelper;
    private static SQLiteDatabase mDb;

    //make sure this matches the 
    //package com.MyPackage;
    //at the top of this file
    private static String DB_PATH = "/data/data/com.MyPackage/databases/";

    //make sure this matches your database name in your assets folder
    // my database file does not have an extension on it 
    // if yours does
    // add the extention
    private static final String DATABASE_NAME = "data";

    //Im using an sqlite3 database, I have no clue if this makes a difference or not
    private static final int DATABASE_VERSION = 3;

    private final Context adapterContext;

    public AnyDBAdapter(Context context) {
        this.adapterContext = context;
    }

    public AnyDBAdapter open() throws SQLException {
        mDbHelper = new DatabaseHelper(adapterContext);

        try {
            mDbHelper.createDataBase();
        } catch (IOException ioe) {
            throw new Error("Unable to create database");
        }

        try {
            mDbHelper.openDataBase();
        } catch (SQLException sqle) {
            throw sqle;
        }
        return this;
    }
    //Usage from outside
    // AnyDBAdapter dba = new AnyDBAdapter(contextObject); //in my case contextObject is a Map
    // dba.open();
    // Cursor c = dba.ExampleSelect("Rawr!");
    // contextObject.startManagingCursor(c);
    // String s1 = "", s2 = "";
    // if(c.moveToFirst())
    // do {
    //  s1 = c.getString(0);
    //  s2 = c.getString(1);
    //  } while (c.moveToNext());
    // dba.close();
    public Cursor ExampleSelect(string myVariable)
    {
        String query = "SELECT locale, ? FROM android_metadata";
        return mDb.rawQuery(query, new String[]{myVariable});
    }

    //Usage
    // AnyDBAdatper dba = new AnyDBAdapter(contextObjecT);
    // dba.open();
    // dba.ExampleCommand("en-CA", "en-GB");
    // dba.close();
    public void ExampleCommand(String myVariable1, String myVariable2)
    {
        String command = "INSERT INTO android_metadata (locale) SELECT ? UNION ALL SELECT ?";
        mDb.execSQL(command, new String[]{ myVariable1, myVariable2});
    }

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

    private static class DatabaseHelper extends SQLiteOpenHelper {

        Context helperContext;

        DatabaseHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
            helperContext = context;
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            Log.w(TAG, "Upgrading database!!!!!");
            //db.execSQL("");
            onCreate(db);
        }

        public void createDataBase() throws IOException {
            boolean dbExist = checkDataBase();
            if (dbExist) {
            } else {

                //make sure your database has this table already created in it
                //this does not actually work here
                /*
                 * db.execSQL("CREATE TABLE IF NOT EXISTS \"android_metadata\" (\"locale\" TEXT DEFAULT 'en_US')"
                 * );
                 * db.execSQL("INSERT INTO \"android_metadata\" VALUES ('en_US')"
                 * );
                 */
                this.getReadableDatabase();
                try {
                    copyDataBase();
                } catch (IOException e) {
                    throw new Error("Error copying database");
                }
            }
        }

        public SQLiteDatabase getDatabase() {
            String myPath = DB_PATH + DATABASE_NAME;
            return SQLiteDatabase.openDatabase(myPath, null,
                    SQLiteDatabase.OPEN_READONLY);
        }

        private boolean checkDataBase() {
            SQLiteDatabase checkDB = null;
            try {
                String myPath = DB_PATH + DATABASE_NAME;
                checkDB = SQLiteDatabase.openDatabase(myPath, null,
                        SQLiteDatabase.OPEN_READONLY);
            } catch (SQLiteException e) {
            }
            if (checkDB != null) {
                checkDB.close();
            }
            return checkDB != null ? true : false;
        }

        private void copyDataBase() throws IOException {

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

            // Path to the just created empty db
            String outFileName = DB_PATH + DATABASE_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();
        }

        public void openDataBase() throws SQLException {
            // Open the database
            String myPath = DB_PATH + DATABASE_NAME;
            mDb = SQLiteDatabase.openDatabase(myPath, null,
                    SQLiteDatabase.OPEN_READWRITE);
        }

        @Override
        public synchronized void close() {

            if (mDb != null)
                mDb.close();

            super.close();

        }
    }

}

Answer 2

DatabaseHelper dbHelper = new DatabaseHelper(getApplicationContext());

Make sure you create DatabaseHelper object once during application lifetime and reuse it.

For reading data:

SQLiteDatabase db = dbHelper.getReadableDatabase();

For reading/modification data:

SQLiteDatabase db = dbHelper.getWritableDatabase();

next use insert(), query(), update(), delete() methods of SQLiteDatabase object:

http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html

You also should not create the database by directly accesssing the sqlite file what you do in createNewDatabase method. Use execSQL() method of SQLiteDatabase object in your onCreate(...) method. Execute your CREATE TABLE queries there.