Use rawQuery() method to get a Cursor on which you don’t have to iterate.
Just check if 1 row is returned because this is what you want to know: if a user exists with the specific login and password:

public boolean checkAuthentication(String login, String password){
    boolean check = false;
    String sql = "SELECT * from Visiteur WHERE vis_login = ? and vis_mdp = ?";
    SQLiteDatabase db = dbManager.getWritableDatabase();
    Cursor cursor = db.rawQuery(sql, new String[] {login, password});
    check = cursor.moveToFirst();
    cursor.close();
    db.close();
    return check;
}

I’m looking to retrieve the result of my request in variables to be able to check if the authentication is correct. In simple sql it does this with a Resultset but I understood that in Sqlite you have to use a Cursor. But I can’t get a result. Here are two examples of what I have already tried :

    public boolean checkAuthentication(String login, String password){

        boolean check = false;

        SQLiteDatabase db = dbManager.getWritableDatabase();
        SQLiteStatement statement = db.compileStatement("SELECT * from Visiteur WHERE vis_login = ? and vis_mdp = ?");
        statement.bindString(1, login);
        statement.bindString(2, password);
        //statement.execute();
        return check;

    }

    public boolean checkAuthentication2(String login, String password){

        boolean check = false;
        String log = null;
        String pass = null;

        String sql = "SELECT * from Visiteur WHERE vis_login = ? and vis_mdp = ?";
        SQLiteStatement statement = db.compileStatement(sql);
        statement.bindString(1, login);
        statement.bindString(2, password);

        Cursor cursor = db.rawQuery(sql, null);

        while(cursor.moveToNext()){
            log =  cursor.getString(cursor.getColumnIndex("vis_login"));
            pass = cursor.getString(cursor.getColumnIndex("vis_mdp"));
            Log.d("WHILE", log);
        }
        cursor.close();
        statement.close();

        if(log != null && pass != null){
            check = true;
        }


        return check;

    }

Thanks for responses.