Android - How to handle 1000 records SQLite

I'm trying to add 1000 records on my SQLite at start, but the thing is that when I launch the APP it turns white screen, then black screen until it crashes, when I put like 5 records, it still doing the same with the white screen and black screen, but when adds the records, it show me a toast with all of the records, so it works... This is my SQLiteBaseAdapter :

public class ClientsSQL extends SQLiteOpenHelper {
// Declaramos la sentencia para crear la tabla
String sqlCreate = "CREATE TABLE Clients(NIF text,cognom1 text,cognom2 text,nom text)";



 public ClientsSQL(Context context, String name, SQLiteDatabase.CursorFactory factory,
                          int version) {
        super(context, name, factory, version);
        // TODO Auto-generated constructor stub
    }
    @Override
    public void onCreate(SQLiteDatabase db) {

        db.execSQL(sqlCreate);
        db.execSQL("INSERT INTO Clients VALUES ('39410028B', 'hola1', 'Hola2', 'Jonathan')");
        Log.v("INFO1", "creating db");


    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub
        // Si existe la tabla, la borramos y la volvemos a crear.
       db.execSQL("DROP TABLE IF EXISTS Clients");
        db.execSQL(sqlCreate);
    }

I created 1 insert as a test, but then on my MainActivity, I did this :

public void crearRegistres(SQLiteDatabase db){

    int i;
    String dni ="";

    for (i = 0; i < 1000; i++) {

        dni = NumeroDNI();

        db.execSQL("INSERT INTO Clients VALUES ('" + dni + "'," + "'cognomA" + i + "'," + "'cognomB" + i + "',"+ "'nom" + i + "')");
    }
    Cursor c;
    c = db.rawQuery("Select NIF from Clients", null);


    Toast.makeText(MainActivity.this, Integer.toString(c.getCount()),
            Toast.LENGTH_LONG).show();
    c.close();
}

I tried to create an Async class, but don't get it, how I call the doInBackGround() method (if it's the way to do it properly...).

EDIT1

This is what I tried, but I can't do nothing, until it finish.

  progress = ProgressDialog.show(getActivity(), "Cargando",
                        "Espere mientras cargan sus ofertas", true);
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            Thread.sleep(2000);


                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }

                        getActivity().runOnUiThread(new Runnable() {

                            @Override
                            public void run() {
                                crearRegistres(db);
                                progress.dismiss();
                            }
                        });
                    }

                }).start();
            }