Android Open Source - hts-cycle Data Base Helper

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License

The source code is released under:

GNU General Public License

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Java Source Code

package it.uniroma2.musicsharep2p;
//w  w  w.java  2 s  .co m
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{

  //Classe delegata al controllo del database
  private static String DB_PATH = "/data/data/it.uniroma2.musicsharep2p/databases/";

  private static String DB_NAME = "Db.sqlite";

  private SQLiteDatabase myDataBase;

  private final Context myContext;

  /**
   * Costruttore
   * Prende e registra il contesto dato per accedere agli assets e alle risorse
   * @param context
   */
  public DataBaseHelper(Context context) {

    super(context, DB_NAME, null, 1);
    this.myContext = context;
  }  


  /**
   * Crea un database vuoto e lo riempie con il database prelevato dagli assets
   * */
  public void createDataBase() throws IOException{

    boolean dbExist = checkDataBase();

    if(dbExist){
      //Il database gi esiste, non fa niente
    }else{

      //Crea il database
      this.getReadableDatabase();

      try {

        copyDataBase();

      } catch (IOException e) {

        throw new Error("Error copying database");

      }
    }

  }

  /**
   * Controlla l'esistenza del Db
   * @return true se esiste, altrimenti false
   */
  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;
  }

  /**
   * Copia il database da assets alla cartella di sistema
   * */
  private void copyDataBase() throws IOException{

    //Apre il database dagli assets come inputstream
    InputStream myInput = myContext.getAssets().open(DB_NAME);

    // Prende il path al database che creato
    String outFileName = DB_PATH + DB_NAME;

    //Lo apre come outputstream
    OutputStream myOutput = new FileOutputStream(outFileName);

    //scrittura di bytes da inputstream a output stream
    byte[] buffer = new byte[1024];
    int length;
    while ((length = myInput.read(buffer))>0){
      myOutput.write(buffer, 0, length);
    }

    //Chiude gli stream
    myOutput.flush();
    myOutput.close();
    myInput.close();

  }

  public void openDataBase() throws SQLException{

    //Apre il Db
    String myPath = DB_PATH + DB_NAME;
    myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

  }

  @Override
  public synchronized void close() {

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

    super.close();

  }

  @Override
  public void onCreate(SQLiteDatabase db) {

  }

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

  }


}

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