Android : After changing orientation progress bar becomes visible all time

OnDownload method called and anyway progress bar is visible. It happens after changing of orientation. I can't find any mistakes there.. I would be really greatful if you helped me with that. The code is shown below:

package com.example.CourseWork2015.activities;

import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

import com.example.CourseWork2015.R;
import com.example.CourseWork2015.utils.ISubjectDownloading;
import com.example.CourseWork2015.utils.MySubjectAdapter;
import com.example.CourseWork2015.utils.Subject;
import com.parse.ParseUser;

import java.util.ArrayList;
import java.util.List;
public class MainActivity extends ListActivity implements ISubjectDownloading {

private static int ADD_SUBJECT_CODE = 0;
private List<Subject> subjects = new ArrayList<>();
private Button addButton;
private ProgressBar progressBar;
private TextView textView;
private MySubjectAdapter adapter;
private final static String SUBJECTS_KEY = "SUBJECTS";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    progressBar = (ProgressBar) findViewById(R.id.progressBar);
    textView = (TextView) findViewById(R.id.textView);
    if (savedInstanceState == null) {
        adapter = new MySubjectAdapter(this, subjects);
        loadSubjectsFromLocalStorage();
        Subject.registerObserver(this);
        setListAdapter(adapter);
    }
    addButton = (Button) findViewById(R.id.newSubject);
    addButton.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this,
                    AddSubjectActivity.class);
            startActivityForResult(intent, ADD_SUBJECT_CODE);
        }
    });
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == ADD_SUBJECT_CODE && resultCode == RESULT_OK
            && data != null) {
        textView.setVisibility(TextView.GONE);
        Bundle bundle = data.getExtras();
        Subject sub = (Subject) bundle
                .getSerializable(AddSubjectActivity.GET_SUBJECT);
        saveSubject(sub);
    }
}

private void saveSubject(Subject sub) {//add & save
    if (!subjects.contains(sub)) {
        sub.saveSubject();
        adapter.notifyDataSetChanged();
    } else {
        Toast.makeText(this, "Subject with this name already exists", Toast.LENGTH_SHORT).show();
    }
}

private void loadSubjectsFromLocalStorage() {
    showProgressBar(true);
    Subject.loadSubjectsFromLocalStorage();
}

private void loadSubjectsFromCloud() {
    showProgressBar(true);
    Subject.loadSubjectsFromCloud();
}

private void showProgressBar(boolean visible) {
    //set progress bar visible or invisible
    if (!visible) {
        progressBar.setVisibility(ProgressBar.GONE);
    } else {
        progressBar.setVisibility(ProgressBar.VISIBLE);
    }
}

private void showMessage(String s) {
    textView.setVisibility(TextView.VISIBLE);
    textView.setText(s);
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putSerializable(SUBJECTS_KEY, (java.io.Serializable) subjects);
}

@Override
protected void onRestoreInstanceState(Bundle state) {
    super.onRestoreInstanceState(state);
    subjects = (List<Subject>) state.getSerializable(SUBJECTS_KEY);
    adapter = new MySubjectAdapter(this, subjects);
    setListAdapter(adapter);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    if (id == R.id.update) {
        loadSubjectsFromCloud();
        return true;
    }
    if (id == R.id.logout) {
        ParseUser.logOut();
        Intent intent = new Intent(this, HomeActivity.class);
        //clear activity stack to prevent use activities use back button
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
        startActivity(intent);
        return true;
    }
    return super.onOptionsItemSelected(item);
}

@Override
public void onDownload(Exception e, List<Subject> subjects) {
    if (e == null) {
        this.subjects.clear();
        this.subjects.addAll(subjects);
        adapter.notifyDataSetChanged();
        if (subjects.size() == 0) {
            showMessage("You have no subjects");
        }

    } else {
        showMessage("Check your internet connection");
    }
    showProgressBar(false);
}

}