Il database Android viene ricreato ogni volta che viene avviata l'applicazione

Question

Perché SQLiteOpenHelper chiama suCreate() ogni volta che si avvia l'applicazione. Ecco il mio codice per onCreate()

@Override 
    public void onCreate(SQLiteDatabase db) { 
     Log.i("onCreate()", "Enter"); 
     //create cards table 
    db.execSQL(   
    "create table circles" + 
    "("+ 
    "id integer primary key,"+ 
    "x integer not null," + 
    "y integer not null"+ 
    ")" 
    );  


    Log.i("onCreate()", "Exit"); 
    } 

Ho una classe al di fuori intorno alla mia classe SQLiteOpenHelper estesa, e quando mi interrogo, faccio questo:

Cursor cursor = openHelper.getWritableDatabase().rawQuery("select * from circles", null); 

e salta questo blocco a causa di questo if

if (cursor.moveToFirst()) {...} 

Ecco tutta la mia classe wrapper Database:

 
package db.main;
 

import java.util.ArrayList; 
import android.content.Context; 
import android.database.Cursor; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 
import android.util.Log; 
import testing.main.Circle;
 

public class DBWrapper {
 

private static final String DATABASE_NAME = "circles.db"; 
    private static final int DATABASE_VERSION = 1; 
    private static final String[] TABLES = new String[] { "circles"};
 

private Context context; 
    private OpenHelper openHelper;
 

public DBWrapper(Context context) { 
     context.deleteDatabase(DATABASE_NAME); 
     this.context = context; 
     this.openHelper = new OpenHelper(this.context); 
    }
 

public void insertCircle(Circle c) 
    { 
     String sql = "insert into circles (x, y) values (" + c.getX() + ", " + c.getY() + ")"; 
     Log.i("DBWrapper::insertCircle()", "Executing sql: " + sql); 
     openHelper.getWritableDatabase().execSQL(sql); 
    }
 

public void clearCircles() 
    { 
     String sql = "delete * from circles"; 
     Log.i("DBWrapper::clearCircles()", "Executing sql: " + sql); 
     openHelper.getWritableDatabase().execSQL(sql); 
    }
 

public ArrayList getCircles() 
    { 
     ArrayList circles = new ArrayList(); 
     Cursor cursor = openHelper.getWritableDatabase().query(TABLES[0], null, null, null, null, null, null); 
     //Cursor cursor = openHelper.getWritableDatabase().rawQuery("select * from circles", null); 
     Log.i("DBWrapper::getCircles()", "move to first1"); 
     if (cursor.moveToFirst()) { 
      Log.i("DBWrapper::getCircles()", "move to first"); 
      do { 
       Log.i("DBWrapper::getCircles()", "Creating circle: " + cursor.getString(1) + ", " + cursor.getString(2)); 
       circles.add(new Circle(Integer.parseInt(cursor.getString(1)), 
            Integer.parseInt(cursor.getString(2)))); 
      } while (cursor.moveToNext()); 
     } 
     if (cursor != null && !cursor.isClosed()) { 
      cursor.close(); 
     } 
     return circles; 
    } 
    private static class OpenHelper extends SQLiteOpenHelper {
 

OpenHelper(Context context) { 
    super(context, DATABASE_NAME, null, DATABASE_VERSION); 
    }  


    @Override 
    public void onCreate(SQLiteDatabase db) { 
     Log.i("OpenHelper::onCreate()", "Enter"); 
     //create cards table 
    db.execSQL(   
    "create table circles" + 
    "("+ 
    "id integer primary key,"+ 
    "x integer not null," + 
    "y integer not null"+ 
    ")" 
    );  


    Log.i("OpenHelper::onCreate()", "Exit"); 
    } 

    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
    Log.w("Example", "Upgrading database, this will drop tables and recreate."); 
    for(String s: TABLES) 
    { 
     db.execSQL("DROP TABLE IF EXISTS " + s); 
    } 
    onCreate(db); 
    } 

}}

Fatemi sapere se ho bisogno di inviare più codice o niente. Grazie.

Answer 1

Guardate il vostro costruttore DBWrapper,

si sta chiamando

context.deleteDatabase(DATABASE_NAME);

Questo eliminerà il file del database ogni volta che si chiama. Forzare SQLHelper per ricreare il database.

Answer 2

Prova questo:

public class DataBaseHelper extends SQLiteOpenHelper { 
    private static final String DATENBANK_NAME = "yourdatabase.db"; 
    private static final int DATENBANK_VERSION = 1; 

    public DataBaseHelper(Context context) { 
     super(context, DATENBANK_NAME, null, DATENBANK_VERSION); 
    } 

    public void onCreate(SQLiteDatabase db) { 
     db.execSQL(PartialTripTbl.SQL_CREATE); 
    } 

    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
     db.execSQL("DROP TABLE IF EXISTS " + PartialTripTbl.TABLE_NAME); 
     onCreate(db); 
    } 

} 

Answer 3

Il collegamento sotto aiuta sperabilmente.

stackoverflow.com -> Query if Adroid DB exists!

Speranza che aiuta

Il manifesto sopra menzionato anche si elimina il database

content.deleteDabase(DATABASE_NAME) 

in voi DBWrapper() costruttore