Android - Abrir un activity desde un AlertDialog

AlertDialog.Builder builder1 = new AlertDialog.Builder(this);

builder1.setCancelable(true);

builder1.setTitle("My Dialogo");

builder1.setMessage("Lanzar Activity");

builder1.setInverseBackgroundForced(true);

builder1.setPositiveButton("Si",

        new DialogInterface.OnClickListener() {

            public void onClick(DialogInterface dialog, int id) {

                Intent intent= new Intent(getApplicationContext(),Activity2.class);

                startActivity(intent);

                dialog.cancel();

            }

        });

builder1.setNegativeButton("No",

        new DialogInterface.OnClickListener() {

            public void onClick(DialogInterface dialog, int id) {

                dialog.cancel();

            }

        });

AlertDialog alert11 = builder1.create();

alert11.show();