Add back key to actionbar

package org.lineageos.openweathermapprovider;

import android.app.ActionBar;

import android.app.Activity;

import android.content.Context;

import android.content.SharedPreferences;

import android.preference.Preference;

import android.preference.PreferenceFragment;

import android.preference.PreferenceManager;

import android.view.MenuItem;

import android.widget.Toast;

import android.widget.Toolbar;

public class SettingsActivity extends Activity {

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        ActionBar actionBar = getActionBar();

        if (actionBar != null) {

            actionBar.setDisplayHomeAsUpEnabled(true);

            actionBar.setHomeAsUpIndicator(R.drawable.ic_back);

        }

        getFragmentManager().beginTransaction()

                .replace(android.R.id.content, new ServicePrefsFragment())

                .commit();

    }

    @Override

    public boolean onOptionsItemSelected(MenuItem item) {

        if (item.getItemId() == android.R.id.home) {

            finish();

        }

        return super.onOptionsItemSelected(item);

    }

    public static class ServicePrefsFragment extends PreferenceFragment implements Preference.OnPreferenceChangeListener {

        private EditTextPreference mApiKeyPreference;

<vector xmlns:android="http://schemas.android.com/apk/res/android"

        android:width="24dp"

        android:height="24dp"

        android:viewportWidth="24.0"

        android:viewportHeight="24.0">

    <path

        android:fillColor="@android:color/white"

        android:pathData="M20,11H7.83l5.59,-5.59L12,4l-8,8 8,8 1.41,-1.41L7.83,13H20v-2z"/>

</vector>