通过扩展BaseActivity在不同的活动中使用导航抽屉

Question

I'm trying to let my HomeActivity extend BaseActivity (as suggested here ) so I can have the same Navigation Drawer in every Activity I want. But I get a NullPointerException in the onCreate method of my HomeActivity. This is the code of BaseActivity:

import android.os.Bundle;
import android.app.Activity;
import android.content.res.Configuration;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.widget.DrawerLayout;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

public class BaseActivity extends Activity
{
    public DrawerLayout drawerLayout;
    public ListView drawerList;
    private String[] drawerListEntries;
    private ActionBarDrawerToggle drawerToggle;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {

        drawerListEntries = new String[] {"Bla bla", "Profile", "Home"};

        drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);

        drawerToggle = new ActionBarDrawerToggle((Activity) this, drawerLayout, R.drawable.ic_navigation_drawer, 0, 0) 
        {
            public void onDrawerClosed(View view) 
            {
                getActionBar().setTitle(R.string.app_name);
            }

            public void onDrawerOpened(View drawerView) 
            {
                getActionBar().setTitle(R.string.hello_world);
            }
        };
        drawerLayout.setDrawerListener(drawerToggle);

        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);

        //layers = getResources().getStringArray(R.array.layers_array);
        drawerList = (ListView) findViewById(R.id.drawer_list);
//        View header = getLayoutInflater().inflate(R.layout.drawer_list_header, null);
//        drawerList.addHeaderView(header, null, false);
        drawerList.setAdapter(new ArrayAdapter<String>(this, R.layout.drawer_list_item, drawerListEntries));
//        View footerView = ((LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(
//                R.layout.drawer_list_footer, null, false);
//        drawerList.addFooterView(footerView);

        drawerList.setOnItemClickListener(new OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int pos, long arg3) {
                //map.drawerClickEvent(pos);
                String selectedValue = (String) drawerList.getAdapter().getItem(pos);
                Toast.makeText(getBaseContext(), selectedValue, Toast.LENGTH_SHORT).show();
            }
        });
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        if (drawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        return super.onOptionsItemSelected(item);

    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        drawerToggle.syncState();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        drawerToggle.onConfigurationChanged(newConfig);
    }
}

And this is the code of HomeActivity which extends BaseActivity:

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.os.Parcelable;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.widget.DrawerLayout;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import com.facebook.Session;

public class HomeActivity extends BaseActivity {

    TextView greeting;
    Button orderButton, deliverButton, logout;

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

        setContentView(R.layout.activity_home);


    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        getMenuInflater().inflate(R.menu.home, menu);
        //return super.onCreateOptionsMenu(menu);
        return true;
    }


}

I get a NullPointerException in:

super.onCreate(savedInstanceState); // HomeActivity

and when I click on that, it goes to:

drawerLayout.setDrawerListener(drawerToggle); // BaseActivity

Does anyone know how I can fix this?

Update:

drawer_list.xml:

<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" >


    <ListView
        android:id="@+id/drawer_list"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_marginBottom="10dp"
        android:layout_marginTop="5dp"
        android:background="@android:color/transparent"
        android:cacheColorHint="@android:color/transparent"
        android:divider="#CCCCCC"
        android:dividerHeight="1dp"
        android:paddingLeft="2dp" />


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

and drawer_list_item.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/drawer_list_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="5dp"
        android:layout_marginTop="12dp" 
        android:textSize="24sp" 
        android:layout_gravity="left"
        android:textColor="@color/belize_hole"
        android:fontFamily="sans-serif-light">
    </TextView>



</LinearLayout>

Answer 1

Same issue in a few posts. I am new to android but solved it this way. Would love to hear if there is a better "right" way to do it. (yes, without fragments but I know I need to learn them eventually).

The problem appears that the base class is not aware of the layout. Not sure how or why it worked for others without having to do something like this.. but I am new to Android.

I was getting the same error and solved by passing my layout to the base via onCreate.

So in the base, I modified onCreate to be like this:

protected void onCreate(Bundle savedInstanceState, int resLayoutID)
{
    super.onCreate(savedInstanceState);
    setContentView(resLayoutID);

Then, from my new activity, I have this:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState, R.layout.my_activity);

This code in my base now works instead of staying null:

drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
drawerList = (ListView) findViewById(R.id.left_drawer);

btw, this result was suggested to me by a friend and it worked for me.