onUpgrade is not being called at first time in android SQLiteOpenHelper

I am facing a very strange problem. I am developing an android application that has an sqlite DB as its database. I am using DBAdapter class which extends SQLiteOpenHelper. I have searched on internet but can't find a solution.

Here is my SQLiteOpenHelper class

public class DBAdapter  extends SQLiteOpenHelper{

         private static DBAdapter mInstance = null;
        /**The Android's default system path of your application database. */
        private static String DB_PATH = "/data/data/com.mydbapp.android/databases/";

        private final static String DB_NAME = "mydb.sqlite";
        private static final int DATABASE_VERSION = 1;
        private static Context myContext;    


        public static DBAdapter getInstance(Context ctx) {

            if (mInstance == null) {
                mInstance = new DBAdapter(ctx);
            }
            return mInstance;
          }
            private DBAdapter(Context context) {     
                super(context,  DB_NAME, null, DATABASE_VERSION);
                DBAdapter.myContext = context;
                     DB_PATH = "/data/data/" +
                             context.getPackageName()+
                "/databases/"; 
            }   

           public void deleteDB()
           {
               myContext.deleteDatabase(DB_NAME);
           }

            public void createDataBase() throws IOException{     
                boolean dbExist = checkDataBase();  
                if(dbExist )
                {
                   this.getWritableDatabase();
                }
                if(!dbExist){
                    this.getReadableDatabase();
                    try {     
                        copyDataBase();
                    } catch (IOException e) {     
                        e.printStackTrace();
                        throw new Error("Error copying database");     
                    }
                }
            }

            @Override
            public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
            {
                if (newVersion > oldVersion)
                {
                            System.out.println("DB Upgrade logic")
                        }
            }

Now when I change private static final int DATABASE_VERSION = 2; then onUpgrade() method doesn't get invoked, but when I change private static final int DATABASE_VERSION = 3; then onUpgrade() works. So my question is that why doesn't it invoke the onUpgrade() method when I change DB version from 1 to 2. Please help me resolve this issue.

Edit 1

I have noticed one more strange behavior. When I initially run application with DB version 1 and then again I install application with sane DB version (1) and now if I change DB version 1 to 2, then onUpgrade() is called. What I mean to say is that I have to install application 2 times with same DB version then if I change DB version, onUpgrade() is called.

Solution

Likely the database you're copying as the initial database already has it's schema version as 2.

Some other issues:

You should store the result of getWritableDatabase() or getReadableDatabase() and close() it when done.
This
```
DB_PATH = "/data/data/" +
         context.getPackageName()+
    "/databases/"
```
won't work on all devices. Don't hardcode database paths. Use getDatabasePath() instead.