Errors in Navigation Drawer Activity

Question

I'm trying to create a navigation drawer for Android. I've followed these pages (this and this) but now I'm stuck.

Here's my code, based on the planet navigation drawer:

package com.example.side_navigation_from_scratch;

import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.SearchManager;
import android.content.Intent;
import android.content.res.Configuration;
import android.os.Bundle;

import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v4.widget.DrawerLayout;

import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;


public class MainActivity extends Activity {
    private DrawerLayout mDrawerLayout;
    private ListView mDrawerList;
    private ActionBarDrawerToggle mDrawerToggle;
    private String mDrawerTitle;
    private String mainTitle;
    private String[] mPlanetTitles;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        setContentView(R.layout.activity_main);
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.activity_main);

        mainTitle = mDrawerTitle = (String) getTitle();

        mPlanetTitles = getResources().getStringArray(R.array.planets_array);
        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerList = (ListView) findViewById(R.id.left_drawer);

        // set up the drawer's list view with items and click listener
        mDrawerList.setAdapter(new ArrayAdapter<String>(this,
                R.layout.drawer_list_item, mPlanetTitles));
        mDrawerList.setOnItemClickListener(new DrawerItemClickListener());

        // ActionBarDrawerToggle ties together the the proper interactions
        // between the sliding drawer and the action bar app icon
        mDrawerToggle = new ActionBarDrawerToggle(
                this,                  /* host Activity */
                mDrawerLayout,         /* DrawerLayout object */
                R.string.drawer_open,  /* "open drawer" description for accessibility */
                R.string.drawer_close  /* "close drawer" description for accessibility */
        ) {
            public void onDrawerClosed(View view) {
                super.onDrawerClosed(view);
                getActionBar().setTitle(mainTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }

            public void onDrawerOpened(View drawerView) {
                super.onDrawerOpened(drawerView);
                getActionBar().setTitle(mDrawerTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }
        };

        mDrawerLayout.setDrawerListener(mDrawerToggle);

        if (savedInstanceState == null) {
            selectItem(0);
        }

        // enable ActionBar app icon to behave as action to toggle nav drawer
        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu_main, menu);
        return super.onCreateOptionsMenu(menu);
    }

    /* Called whenever we call invalidateOptionsMenu() */
    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        // If the nav drawer is open, hide action items related to the content view
        boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
        menu.findItem(R.id.action_websearch).setVisible(!drawerOpen);
        return super.onPrepareOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // The action bar home/up action should open or close the drawer.
        // ActionBarDrawerToggle will take care of this.
        if (mDrawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        // Handle action buttons
        switch(item.getItemId()) {
            case R.id.action_websearch:
                // create intent to perform web search for this planet
                Intent intent = new Intent(Intent.ACTION_WEB_SEARCH);
                intent.putExtra(SearchManager.QUERY, getActionBar().getTitle());
                // catch event that there's no activity to handle intent
                if (intent.resolveActivity(getPackageManager()) != null) {
                    startActivity(intent);
                } else {
                    Toast.makeText(this, R.string.app_not_available, Toast.LENGTH_LONG).show();
                }
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

    /* The click listner for ListView in the navigation drawer */
    private class DrawerItemClickListener implements ListView.OnItemClickListener {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            selectItem(position);
        }
    }

    private void selectItem(int position) {
        // update the main content by replacing fragments
        Fragment fragment = new PlanetFragment();
        Bundle args = new Bundle();
        args.putInt(PlanetFragment.ARG_PLANET_NUMBER, position);
        fragment.setArguments(args);

        FragmentManager fragmentManager = getFragmentManager();
        fragmentManager.beginTransaction().replace(R.id.content_frame, fragment).commit();

        // update selected item and title, then close the drawer
        mDrawerList.setItemChecked(position, true);
        setTitle(mPlanetTitles[position]);
        mDrawerLayout.closeDrawer(mDrawerList);
    }

    @Override
    public void setTitle(CharSequence title) {
        mainTitle = (String) title;
        getActionBar().setTitle(mainTitle);
    }

    /**
     * When using the ActionBarDrawerToggle, you must call it during
     * onPostCreate() and onConfigurationChanged()...
     */

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        // Sync the toggle state after onRestoreInstanceState has occurred.
        mDrawerToggle.syncState();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        // Pass any configuration change to the drawer toggls
        mDrawerToggle.onConfigurationChanged(newConfig);
    }

    /**
     * Fragment that appears in the "content_frame", shows a planet
     */
    public static class PlanetFragment extends Fragment {
        public static final String ARG_PLANET_NUMBER = "planet_number";

        public PlanetFragment() {
            // Empty constructor required for fragment subclasses
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_planet, container, false);
            int i = getArguments().getInt(ARG_PLANET_NUMBER);
            String planet = getResources().getStringArray(R.array.planets_array)[i];
            TextView planetName = (TextView) rootView.findViewById(R.id.text);

            getActivity().setTitle(planet);
            return rootView;
        }
    }
}

I get different errors depending on the changes I make. Like it is right now, I get

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference

ActionBarActivity is deprecated so I'm not going to use it but if I change Activity to AppCompatActivity, I get

java.lang.IllegalArgumentException: AppCompat does not support the current theme features

What am I doing wrong? Which is better to use: Activity, ActionBarActivity or AppCompatActivity? Thanks in advance

Answer 1

Thanks to Raghunandan I managed to fix this: I changed the Activity to AppCompatActivity and replaced getActionBar for getSupportActionBar. I don't have any more NPE