Lendo banco de dados SQLite no Android

Lendo banco de dados SQLite no Android

Caso um banco de dados SQLite já exista, para usá-lo num aplicativo Android:

a) Criar a classe DataBaseHelper:

package fhu.com.br;
 
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
 
import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
 
public class DataBaseHelper extends SQLiteOpenHelper{
 
    // Android's folder for all your databases. You only have to change
	// "fhu.com.br" to match yours
    private static String DB_PATH = "/data/data/fhu.com.br/databases/";
 
    // Name of the database file
    private static String DB_NAME = "nomebanco.sqlite";
 
    // Internal variables
    private SQLiteDatabase dbHandle; 
    private final Context dbContext;
 
    /**
     * 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, 1);
        this.dbContext = context;
    }	
 
    /**
     * Creates a empty database on the system and rewrites it with your own database.
     * */
    public void createDataBase() throws IOException {
 
    	// Verifies if the database already exist
    	boolean dbExist = checkDataBase();
 
    	if (!dbExist) {
 
    		// 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 {
     			this.copyDataBase();
     		} catch (IOException e) {
         		throw new Error("Erro ao copiar banco de dados");
         	}
    	}
     }
 
    /**
     * Check if the database already exist to avoid re-copying the file each time you open the application.
     * @return true if it exists, false if it doesn't
     */
    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.
     	}
 
    	if (checkDB != null) {
     		checkDB.close();
     	}
 
    	return checkDB != null ? true : false;
    }
 
    /**
     * Copies your database from your local assets-folder to the just created empty database in the
     * system folder, from where it can be accessed and handled.
     * This is done by transfering bytestream.
     * */
    private void copyDataBase() throws IOException{
 
    	// Openn local db as the input stream
    	InputStream myInput = dbContext.getAssets().open(DB_NAME);
 
    	// Path to the just created empty db
    	String outFileName = DB_PATH + DB_NAME;
 
    	// Opens the empty db as the output stream
    	OutputStream myOutput = new FileOutputStream(outFileName);
 
    	// Transfers 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);
    	}
 
    	// Closes the streams
    	myOutput.flush();
    	myOutput.close();
    	myInput.close();
 
    }
 
    public void openDataBase() throws SQLException{
     	// Open the database
        String myPath = DB_PATH + DB_NAME;
        dbHandle = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
     }
 
    @Override
	public synchronized void close() {
     	if (dbHandle != null)
     		dbHandle.close();
     	super.close();
 	}
 
	@Override
	public void onCreate(SQLiteDatabase dbHandle) {
 
	}
 
	@Override
	public void onUpgrade(SQLiteDatabase dbHandle, int oldVersion, int newVersion) {
 
	}
}

b) Copiar o arquivo nomebanco.sqlite para o folder /assets/ do projeto Android.

c) Na classe principal do aplicativo (Activity):

DataBaseHelper myDbHelper;
myDbHelper = new DataBaseHelper(this);
 
try {
    myDbHelper.createDataBase();
} catch (IOException ioe) {
    throw new Error("Não foi possível criar o banco de dados.");
}
 
try {
    myDbHelper.openDataBase();
} catch (SQLException sqle){
    throw sqle;
}

NOTA: O plugin do Firefox SQLite Manager ou o aplicativo SQLite Database Browser são dois bons aplicativos gerenciadores de banco de dados SQLite, ambos gratuitos.

FONTE: Conteúdo original deste artigo em Using your own SQLite database in Android applications.