如何更新爲android創建的sqlite數據庫？

Question

我正在創建一個需要數據庫的應用程序。我使用sqlite數據庫瀏覽器創建了它，這意味着我創建的應用程序將我創建的數據庫導入到手機中。

以及我以前學過的東西，如果我使用瀏覽器對數據庫做了任何更改，我必須從手機/模擬器中卸載應用程序，以便進行更改。

所以問題來了。如果我將應用程序上傳到市場後發生什麼情況，並意識到我需要更新表？另一個問題是用戶必須輸入一些數據並將其保存到數據庫的表中。

那麼有沒有辦法更新我的數據庫&還保留用戶在表中輸入的數據？

我的數據庫幫助代碼如下。請幫助...非常感謝！

public class DatabaseHelper extends SQLiteOpenHelper { 

//The Android's default system path of your application database. 
private static String DB_PATH = "/data/data/test.test/databases/"; 

private static String DB_NAME = "TestDatabase"; 

private static final int DB_VERSION = 1; 

private SQLiteDatabase myDatabase; 

private final Context myContext; 

/** 
* # 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, DB_VERSION); 
    this.myContext = context; 
}//constructor 

/** 
* # Create Database # 
* Creates a empty database on the system and rewrites it with your own database. 
*/ 
public void createDatabase() throws IOException { 

    boolean dbExist = checkDatabase(); 

    if(dbExist) 
    { 
     //do nothing - database already exist 
    }//if 

    else 
    { 
     //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 
     { 
      copyDatabase(); 

     } catch (IOException e) { 

      throw new Error("Error copying database"); 

     }//catch 
    }//else 

}//createDatabase 

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. 

    }//catch 

    if(checkDB != null) 
    { 
     checkDB.close(); 

    }//if 

    return checkDB != null ? true : false; 

}//checkDatabase 


private void copyDatabase() throws IOException { 

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

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

}//copyDatabase 

// # open database # 
public void openDatabase() throws SQLException { 

    //Open the database 
    String myPath = DB_PATH + DB_NAME; 
    myDatabase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE); 

}//openDatabase 

@Override 
public synchronized void close() 
{ 
    if(myDatabase != null) 
     myDatabase.close(); 

    super.close(); 

}//close 

@Override 
public void onCreate(SQLiteDatabase db) { 

} 

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

} 

public List<String> selectData 
    (String tableName, String [] columns, String selection, String[] selectionArgs, 
      String groupBy, String having, String orderBy) { 

    List<String> list = new ArrayList<String>(); 

    Cursor cursor = this.myDatabase.query(tableName, columns, selection, selectionArgs, groupBy, having, orderBy); 

    if (cursor.moveToFirst()) 
    { 
     do 
     { 
      list.add(cursor.getString(0)); 
     } 

     while (cursor.moveToNext()); 
    } 

    if (cursor != null && !cursor.isClosed()) 
    { 
     cursor.close(); 
    } 
    return list; 

}//selectData 

public void insertData (String tableName, String nullColumnHack, ContentValues values) { 

    try 
    { 
     myDatabase.insert(tableName, nullColumnHack, values); 
    } catch (Exception e) { 
     Log.e("Error :","unable to insert data"); 
    }//catch 

}//insertData 

//edit row 
public void updateData (String tableName, ContentValues values, String whereClause, String[] whereArgs) { 

    try 
    { 
     myDatabase.update(tableName, values, whereClause, whereArgs); 
    } catch (Exception e) { 
     Log.e("Error :","unable to update data"); 
    }//catch 
}//updateData 

public void deleteRow (String tableName, String whereClause, String[] whereArgs) { 

    try 
    { 
     myDatabase.delete(tableName, whereClause, whereArgs); 
    } catch (Exception e) { 
     Log.e("Error :","unable to delete row"); 
    }//catch 
}//deleteRow 
} 

Answer 1

那就是：

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

} 

是。

Documentation here.