datePicker benutzen um den ausgewählten Tag zu bekommen

package com.example.de.sasitravel;


import android.app.DatePickerDialog;
import android.app.Dialog;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.design.widget.BottomNavigationView;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.DatePicker;
import java.text.DateFormat;
import java.util.Calendar;
import java.util.GregorianCalendar;
import android.support.v4.app.DialogFragment;
import android.widget.TextView;




public class FlightActivity extends AppCompatActivity implements DatePickerDialog.OnDateSetListener{


    UserLocalStore userLocalStore;
    Boolean isReturn = false;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_flight);


        userLocalStore = new UserLocalStore(this);
        BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.top_NavView_bar);
        BottomNavigationViewHelper.disableShiftMode(bottomNavigationView);
        Menu menu = bottomNavigationView.getMenu();
        MenuItem menuItem = menu.getItem(1);
        menuItem.setChecked(true);
        bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener(){
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                switch (item.getItemId()){


                    case R.id.action_profile:
                        startActivity(new Intent(FlightActivity.this, ProfileActivity.class));
                        break;
                    case R.id.action_flight:
                        break;
                    case R.id.action_hotel:
                        startActivity(new Intent(FlightActivity.this, HotelActivity.class));
                        break;
                }
                return false;


            }
        });
    }


    @Override
    protected void onStart() {
        super.onStart();
        //startActivity(new Intent(this, LoginActivity.class));
        if(authenticate() == false){
        }else {startActivity(new Intent(this, LoginActivity.class));}
    }


    private boolean authenticate(){
        return userLocalStore.getUserLoggedIn();
    }


    public void onClickOneWay(View v){
        setContentView(R.layout.activity_one_way);
    }


    public void onClickReturn(View v){
        setContentView(R.layout.activity_flight);
    }


    public void datePicker(View view){
        DatePickerFragment fragment = new DatePickerFragment();
        fragment.show(getSupportFragmentManager(), "date");
    }


    public void datePickerReturn(View view){
        isReturn = true;
        DatePickerFragment fragment = new DatePickerFragment();
        fragment.show(getSupportFragmentManager(), "date");
    }


    private void setDate(final Calendar calendar) {
        final DateFormat dateFormat = DateFormat.getDateInstance(DateFormat.MEDIUM);
        if (!isReturn) {
            ((TextView) findViewById(R.id.tvDate)).setText(dateFormat.format(calendar.getTime()));
            //((TextView) findViewById(R.id.tvDay)).setText(dateFormat.format(calendar.getTime()));
        }else{
            ((TextView) findViewById(R.id.tvDateReturn)).setText(dateFormat.format(calendar.getTime()));
        }
    }


    @Override
    public void onDateSet(DatePicker view, int year, int month, int day) {
        Calendar calendar = new GregorianCalendar(year,month,day);
        Log.d("VIVZ", "day of week "+day );
        setDate(calendar);
    }


    public static class DatePickerFragment extends DialogFragment{
        @NonNull
        @Override
        public Dialog onCreateDialog(Bundle savedInstanceState) {
            final Calendar calendar = Calendar.getInstance();
            int year = calendar.get(Calendar.YEAR);
            int month = calendar.get(Calendar.MONTH);
            int day = calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH);


            return new DatePickerDialog(getActivity(), (DatePickerDialog.OnDateSetListener) getActivity(),year,month,day);


        }
    }
}

private void setDate(final Calendar calendar) {
        String daysArray[] = {"Sunday","Monday","Tuesday", "Wednesday","Thursday","Friday", "Saturday"};
        int day = calendar.get(Calendar.DAY_OF_WEEK);
        String selectedDay = daysArray[day-1];
        final DateFormat dateFormat = DateFormat.getDateInstance(DateFormat.MEDIUM);
        if (!isReturn) {
            ((TextView) findViewById(R.id.tvDate)).setText(dateFormat.format(calendar.getTime()));
            ((TextView) findViewById(R.id.tvDay)).setText(selectedDay);
        }else{
            ((TextView) findViewById(R.id.tvDateReturn)).setText(dateFormat.format(calendar.getTime()));
            ((TextView) findViewById(R.id.tvDayReturn)).setText(selectedDay);
        }
    }