java - App crashed after adding navigation menu in Android Studio

Question

Please take a look at my source code, my app crashed after I added the navigation Menu. Can you please tell what is wrong I have been searching all on Google and could not arrive at a solution to this issue? Thank You.

My MainActivity looks like:

package com.example.rssreader;
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.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.support.v7.app.ActionBar;
import android.view.LayoutInflater;
import android.view.MenuInflater;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.Toast;

import java.util.Locale;

public class MainActivity extends AppCompatActivity {
    private DrawerLayout mDrawerLayout;
    private ListView mDrawerList;
    private android.support.v4.app.ActionBarDrawerToggle mDrawerToggle;

    private CharSequence mDrawerTitle;
    private CharSequence mTitle;
    private String[] mPlanetTitles;
    RecyclerView recyclerView;

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


        recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
        ReadRss readRss = new ReadRss(this, recyclerView);
        readRss.execute();

        mTitle = mDrawerTitle = getTitle();
        mPlanetTitles = getResources().getStringArray(R.array.contents);
        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerList = (ListView) findViewById(R.id.left_drawer);

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setHomeButtonEnabled(true);

        // set a custom shadow that overlays the main content when the drawer opens
        mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
        // 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());

        // enable ActionBar app icon to behave as action to toggle nav drawer


        // ActionBarDrawerToggle ties together the the proper interactions
        // between the sliding drawer and the action bar app icon
        mDrawerToggle = new android.support.v4.app.ActionBarDrawerToggle(
                this,                  /* host Activity */
                mDrawerLayout,         /* DrawerLayout object */
                R.drawable.ic_drawer,  /* nav drawer image to replace 'Up' caret */
                R.string.drawer_open,  /* "open drawer" description for accessibility */
                R.string.drawer_close  /* "close drawer" description for accessibility */
        ) {
            public void onDrawerClosed(View view) {
                getActionBar().setTitle(mTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }

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

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

        getWindow().setNavigationBarColor(getResources().getColor(R.color.colorPrimary));



    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.layout.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);
                // 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_CONTENT_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) {
        mTitle = title;
        getActionBar().setTitle(mTitle);
    }

    /**
     * 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_CONTENT_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_content, container, false);
            int i = getArguments().getInt(ARG_CONTENT_NUMBER);
            String planet = getResources().getStringArray(R.array.contents)[i];

            int imageId = getResources().getIdentifier(planet.toLowerCase(Locale.getDefault()),
                    "drawable", getActivity().getPackageName());
            ((ImageView) rootView.findViewById(R.id.image)).setImageResource(imageId);
            getActivity().setTitle(planet);
            return rootView;

        }
    }

}

My Activity_main.xml looks like:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >

    <FrameLayout
        android:id="@+id/content_frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />


    <ListView
        android:id="@+id/left_drawer"
        android:layout_width="240dp"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:choiceMode="singleChoice"
        android:divider="@android:color/transparent"
        android:dividerHeight="0dp"
        android:background="#ccc"/>

</android.support.v4.widget.DrawerLayout>

Drawer_list_item.xml looks like:

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/text1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceListItemSmall"
    android:gravity="center_vertical"
    android:paddingLeft="16dp"
    android:paddingRight="16dp"
    android:textColor="#113d5e"
    android:background="?android:attr/activatedBackgroundIndicator"
    android:minHeight="?android:attr/listPreferredItemHeightSmall"/>

Fragment_content.xml looks like:

<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/image"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000"
    android:gravity="center"
    android:padding="32dp" />

Main.xml looks like:

<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/image"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000"
    android:gravity="center"
    android:padding="32dp" />

Thank You

Answer 1

I was able to fix that issue by creating a separate class for the navigation drawer. However, I am facing another issue with the RssFeeds.

public class ReadRss extends AsyncTask and recyclerView.setLayoutManager(new LinearLayoutManager(context) is where the error is pointing to when the app crashed when running the debug.

Here is the ReadRss.java:

package tk.mattercast.myapplication;

import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;


public class ReadRss extends AsyncTask<Void, Void, Void> {
    Context context;
    String address = "http://www.oecd.org/corruption/index.xml";
    ProgressDialog progressDialog;
    ArrayList<FeedItem>feedItems;
    RecyclerView recyclerView;
    URL url;
    public ReadRss(Context context,RecyclerView recyclerView) {
        this.recyclerView=recyclerView;
        this.context = context;
        progressDialog = new ProgressDialog(context);
        progressDialog.setMessage("Fetching Data...");
    }

    @Override
    protected void onPreExecute() {
        progressDialog.show();
        super.onPreExecute();
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);
        progressDialog.dismiss();
        MyAdapter adapter=new MyAdapter(context,feedItems);
        recyclerView.setLayoutManager(new LinearLayoutManager(context) {
            @Override
            public RecyclerView.LayoutParams generateDefaultLayoutParams() {
                return null;
            }
        });
        recyclerView.addItemDecoration(new VerticalSpace(50));
        recyclerView.setAdapter(adapter);

    }

    @Override
    protected Void doInBackground(Void... params) {
        ProcessXml(Getdata());

        return null;
    }

    private void ProcessXml(Document data) {
        if (data != null) {
            feedItems=new ArrayList<>();
            Element root = data.getDocumentElement();
            Node channel = root.getChildNodes().item(1);
            NodeList items = channel.getChildNodes();
            for (int i = 0; i < items.getLength(); i++) {
                Node cureentchild = items.item(i);
                if (cureentchild.getNodeName().equalsIgnoreCase("item")) {
                    FeedItem item=new FeedItem();
                    NodeList itemchilds = cureentchild.getChildNodes();
                    for (int j = 0; j < itemchilds.getLength(); j++) {
                        Node cureent = itemchilds.item(j);
                        if (cureent.getNodeName().equalsIgnoreCase("title")){
                            item.setTitle(cureent.getTextContent());
                        }else if (cureent.getNodeName().equalsIgnoreCase("description")){
                            item.setDescription(cureent.getTextContent());
                        }else if (cureent.getNodeName().equalsIgnoreCase("pubDate")){
                            item.setPubDate(cureent.getTextContent());
                        }else if (cureent.getNodeName().equalsIgnoreCase("link")){
                            item.setLink(cureent.getTextContent());
                        }
                    }
                    feedItems.add(item);





                }
            }
        }
    }

    public Document Getdata() {
        try {
            url = new URL(address);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            InputStream inputStream = connection.getInputStream();
            DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
            DocumentBuilder builder = builderFactory.newDocumentBuilder();
            Document xmlDoc = builder.parse(inputStream);
            return xmlDoc;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }


}