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In my previous post about SQLite , I only post the way to create database when application started.

In reality, we do not only need a database to store data but also need one to read information from.

So, in this post, I will show you how to use existing SQLite database in Android app.

The basic idea for this case is instead of creating a new database, we copy the exist one to the application’s data folder.

Very simple, right?

Now, we’ll go straight to the demo for easier understanding.

First, create a Test database:

Enter some dummy data:

The very first thing you need to do when you want to use SQLite is create a sub class of SQLiteOpenHelper.

Create some constants for database name, table name, and the database path:

public class DatabaseHelper extends SQLiteOpenHelper {

    public static String DB_PATH = "/data/data/ice.tea09.sqlitedemo/databases/";

    public static String DB_NAME = "Test.sqlite"; public static final int DB_VERSION = 1;

    public static final String TB_USER = "Users";

}

 

Note that ice.tea09.splitedemo is your project namespace.

Implement constructor, and some methods of super class:

private SQLiteDatabase myDB;
private Context context;

public DatabaseHelper(Context context) {
    super(context, DB_NAME, null, DB_VERSION);
    this.context = context;
}

@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub

}

@Override
public synchronized void close(){
    if(myDB!=null){
        myDB.close();
    }
    super.close();
}

 

Method checkDatabase() allow you to check if the database exists on the phone or not:

 

/***
* Check if the database is exist on device or not
* @return
*/
private boolean checkDataBase() {
    SQLiteDatabase tempDB = null;
    try {
        String myPath = DB_PATH + DB_NAME;
        tempDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
    } catch (SQLiteException e) {
        Log.e("tle99 - check", e.getMessage());
    }
    if (tempDB != null)
        tempDB.close();
    return tempDB != null ? true : false;
}

Method copyDatabase() used to copy SQLite file in assets folder to data folder of application on the phone:

/***
 * Copy database from source code assets to device
 * @throws IOException
 */
public void copyDataBase() throws IOException{
    try {
        InputStream myInput = context.getAssets().open(DB_NAME);
        String outputFileName = DB_PATH + DB_NAME;
        OutputStream myOutput = new FileOutputStream(outputFileName);

        byte[] buffer = new byte[1024];
        int length;

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

        myOutput.flush();
        myOutput.close();
        myInput.close();
    } catch (Exception e) {
        Log.e("tle99 - copyDatabase", e.getMessage());
    }

}

openDatabase() method:

/***
 * Open database
 * @throws SQLException
 */
public void openDataBase() throws SQLException{
    String myPath = DB_PATH + DB_NAME;
    myDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
}

 

Finally, createDatabase() method - which will be called every time we launch app. It will check if the database does not exist on the phone, It’ll copy the database to data folder of application:

/***
 * Check if the database doesn't exist on device, create new one
 * @throws IOException
 */
public void createDataBase() throws IOException {
    boolean dbExist = checkDataBase();        

    if (dbExist) {

    } else {
        this.getReadableDatabase();
        try {
            copyDataBase();
        } catch (IOException e) {
            Log.e("tle99 - create", e.getMessage());
        }
    }
}

 

Finally, method that help you retrieve data from database:

public List<String> getAllUsers(){
    List<String> listUsers = new ArrayList<String>();
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor c;

    try {
        c = db.rawQuery("SELECT * FROM " + TB_USER , null);
        if(c == null) return null;

        String name;
        c.moveToFirst();
        do {            
            name = c.getString(1);            
            listUsers.add(name);
        } while (c.moveToNext()); 
        c.close();
    } catch (Exception e) {
        Log.e("tle99", e.getMessage());
    }

    db.close();        

    return listUsers;
}

 

The way we using DatabaseHelper in MainActivity:

public class MainActivity extends Activity {

    DatabaseHelper dbHeplper;
    ListView lvUsers;
    ListAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        dbHeplper = new DatabaseHelper(getApplicationContext());
        try {
            dbHeplper.createDataBase();
        } catch (IOException e) {
            e.printStackTrace();
        }

        lvUsers = (ListView)findViewById(id.lvUsers);
         List<String> listUsers = dbHeplper.getAllUsers();

        if(listUsers != null){
            adapter = new ArrayAdapter<String>(getApplicationContext(),
                    android.R.layout.simple_list_item_1, android.R.id.text1,
                    listUsers);
            lvUsers.setAdapter(adapter);
        }

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

 

Demo result:

Source code:


https://drive.google.com/file/d/0BzvV1wN-WHWwWG5LQm01ZnNJTzQ/edit?usp=sharing