Change the theme of the activity from a fragment

I need you to change the theme of my MainActivity when entering a Fragment

HomeFragment.java

getActivity().setTheme(R.style.SoonticketThemeMain);

So far that has not worked for me

This is my Activity

package com.soonticket.activity;

import android.content.Context;
import android.content.SharedPreferences;
import android.graphics.Typeface;
import android.os.Bundle;
import android.support.design.widget.NavigationView;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.AppCompatActivity;
import android.text.Spannable;
import android.text.SpannableString;
import android.view.Menu;
import android.view.MenuItem;
import android.view.SubMenu;
import android.view.ViewGroup;
import android.widget.Toast;

import com.soonticket.R;
import com.soonticket.fragments.Home;
import com.soonticket.fragments.Profile;
import com.soonticket.util.CustomTypefaceSpan;
import com.soonticket.util.FontChangeCrawler;

public class MainActivity extends AppCompatActivity {
    SharedPreferences prefs = null;
    Menu ActivityMenu;

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

        FontChangeCrawler fontChanger = new FontChangeCrawler(getAssets(), "fonts/segoeui.ttf");
        fontChanger.replaceFonts((ViewGroup) this.findViewById(android.R.id.content));

        NavigationView navigationView = (NavigationView) findViewById(R.id.navigation_main_view);
        setupDrawerContent(navigationView);

        ActivityMenu = navigationView.getMenu();

        for (int i = 0; i < ActivityMenu.size(); i++) {
            MenuItem mi = ActivityMenu.getItem(i);

            //for aapplying a font to subMenu ...
            SubMenu subMenu = mi.getSubMenu();
            if (subMenu != null && subMenu.size() > 0) {
                for (int j = 0; j < subMenu.size(); j++) {
                    MenuItem subMenuItem = subMenu.getItem(j);
                    applyFontToMenuItem(subMenuItem);
                }
            }

            //the method we have create in activity
            applyFontToMenuItem(mi);
        }

        if (savedInstanceState == null) {
            FragmentManager fragmentManager = getSupportFragmentManager();
            fragmentManager.beginTransaction().replace(R.id.main_frame, new Home()).commit();
        }
    }

    private void applyFontToMenuItem(MenuItem mi) {
        Typeface font = Typeface.createFromAsset(getAssets(), "fonts/segoeui.ttf");
        SpannableString mNewTitle = new SpannableString(mi.getTitle());
        mNewTitle.setSpan(new CustomTypefaceSpan("", font), 0, mNewTitle.length(), Spannable.SPAN_INCLUSIVE_INCLUSIVE);
        mi.setTitle(mNewTitle);
    }

    private void setupDrawerContent(NavigationView navigationView) {
        navigationView.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        selectDrawerItem(menuItem);
                        return true;
                    }
                });
    }

    public void selectDrawerItem(MenuItem menuItem) {

        NavigationView navigationView = (NavigationView) findViewById(R.id.navigation_main_view);
        ActivityMenu = navigationView.getMenu();

        // Create a new fragment and specify the fragment to show based on nav item clicked
        Fragment fragment = null;
        Class fragmentClass = null;
        switch (menuItem.getItemId()) {
            case R.id.nav_account:
                fragmentClass = Profile.class;
                break;
            case R.id.nav_favorites:
                Toast.makeText(this, menuItem.getTitle(), Toast.LENGTH_LONG).show();
                break;
            default:
                Toast.makeText(this, menuItem.getTitle(), Toast.LENGTH_LONG).show();
                break;
        }

        try {
            fragment = (Fragment) fragmentClass.newInstance();

            // Insert the fragment by replacing any existing fragment
            FragmentManager fragmentManager = getSupportFragmentManager();
            fragmentManager.beginTransaction().replace(R.id.main_frame, fragment).commit();
        } catch (Exception e) {
            e.printStackTrace();
        }

        // Highlight the selected item has been done by NavigationView
        menuItem.setChecked(true);

        // Close the navigation drawer
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    public void openDrawer() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.openDrawer(GravityCompat.START);
    }
}

And this is my fragment

package com.soonticket.fragments;

import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RelativeLayout;

import com.soonticket.R;
import com.soonticket.activity.MainActivity;
import com.soonticket.util.FontChangeCrawler;

public class Home extends Fragment {

    RelativeLayout DrawerButtonHome;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        final View rootView = inflater.inflate(R.layout.fragment_home, container, false);

        FontChangeCrawler fontChangeScrollToolbar = new FontChangeCrawler(getActivity().getAssets(), "fonts/r_medium.ttf");
        fontChangeScrollToolbar.replaceFonts((ViewGroup) rootView.findViewById(R.id.scroll_toolbar));

        Toolbar toolbar = (Toolbar) rootView.findViewById(R.id.home_toolbar);
        ((AppCompatActivity) getActivity()).setSupportActionBar(toolbar);
        ((AppCompatActivity) getActivity()).getSupportActionBar().setDisplayShowTitleEnabled(false);

        DrawerButtonHome = (RelativeLayout) rootView.findViewById(R.id.drawer_button_home);
        DrawerButtonHome.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                ((MainActivity) getActivity()).openDrawer();
            }
        });

        return rootView;
    }
}