プログレス表示(IllegalStateException: Can not perform this action after onSaveInstanceState 対策済)

MainActivity.java

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        findViewById(R.id.execute).setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                startProgressTask();
            }
        });
    }

    private void startProgressTask() {
        new ProgressTask().execute();
    }

    class ProgressTask extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            showProgress();
        }

        @Override
        protected Void doInBackground(Void... params) {
            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            hideProgress();
        }
    }

    private static final String TAG_PROGRESS = "progress";

    private void showProgress() {
        DialogFragment dialog = new ProgressDialogFragment();

        // 例外対策
        // IllegalStateException: Can not perform this action after onSaveInstanceState
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        ft.add(dialog, TAG_PROGRESS);
        ft.commitAllowingStateLoss();
    }

    private void hideProgress() {
        Fragment fragment = getFragmentManager().findFragmentByTag(TAG_PROGRESS);
        if (fragment == null || !(fragment instanceof DialogFragment)) {
            return;
        }
        ((DialogFragment) fragment).dismissAllowingStateLoss();
    }
}

ProgressDialogFragment.java

public class ProgressDialogFragment extends DialogFragment {

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        setCancelable(false);

        ProgressDialog dialog = new ProgressDialog(getActivity());
        dialog.setMessage("処理中..");
        dialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);

        return dialog;
    }
}