Android Error [Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)]

Question

I am trying to create a menu activity that uses a navigation drawer. At first I was using the getActionBar() and then i found out that i was supposed to change to getSupportActionBar() and extend AppCompactActivity which iI did but I still seem to be getting the same error:

java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)'
on a null object reference

could anyone know what could be causing the issue. (Please let me know if i should upload any code)

Here is my corresponding code:

    mTitle = mDrawerTitle = getTitle();

    // load slide menu items
    navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items);

    // nav drawer icons from resources
    navMenuIcons = getResources()
            .obtainTypedArray(R.array.nav_drawer_icons);

    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
    mDrawerList = (ListView) findViewById(R.id.list_slidermenu);

    navDrawerItems = new ArrayList<NavDrawerItem>();

    // adding nav drawer items to array
    // Home
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1)));
    // Find People
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1)));
    // Photos
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1)));
    // Communities, Will add a counter here
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1), true, "22"));
    // Pages
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1)));
    // What's hot, We  will add a counter here
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1), true, "50+"));


    // Recycle the typed array
    navMenuIcons.recycle();

    // setting the nav drawer list adapter
    adapter = new NavDrawerListAdapter(getApplicationContext(),
            navDrawerItems);
    mDrawerList.setAdapter(adapter);

    // enabling action bar app icon and behaving it as toggle button
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setHomeButtonEnabled(true);

    mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
            R.drawable.ic_drawer, //nav menu toggle icon
            R.string.app_name, // nav drawer open - description for accessibility
            R.string.app_name // nav drawer close - description for accessibility
    ){
        public void onDrawerClosed(View view) {
            getSupportActionBar().setTitle(
                    Html.fromHtml("<font color=\"black\">" + mTitle + "</font>"));

            // calling onPrepareOptionsMenu() to show action bar icons
            invalidateOptionsMenu();
        }

        public void onDrawerOpened(View drawerView) {
            getSupportActionBar().setTitle(
                    Html.fromHtml("<font color=\"black\">" + mDrawerTitle + "</font>"));

            // calling onPrepareOptionsMenu() to hide action bar icons
            invalidateOptionsMenu();
        }
    };
    mDrawerLayout.setDrawerListener(mDrawerToggle);

    if (savedInstanceState == null) {
        // on first time display view for first nav item
        //displayView(0);
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_menu, menu);
    return true;
}

Possible duplicate of [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it) — Selvin, Mar 16 '16 at 11:36
Your getSupportActionBar() returns null means you have to create toolBar first and then you have to set it as ActionBar using setSupportActionBar(Toolbar toolbar) then call setDisplayHomeAsUpEnabled(Boolean boolean) method on toolbars reference — Abhishek, Mar 16 '16 at 11:41

score 0 · Answer 1 · answered Mar 16 '16 at 11:47

In your onCreate method do the following

public class ActivityDemo extends AppCompatActivity{
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_demo);

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setHomeButtonEnabled(true);
        //other statements
   }
   @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                this.finish();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
   }

Corresponding xml should be having content like this

<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"

    tools:context="com.dev.ActivityDemo">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay"
        android:id="@+id/settingsToolBar"
        >

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/AppTheme.PopupOverlay" />

    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/content_settings"
        />

Android Error [Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)]

1 Answers1