CODEWITHSUNDEEP
javaandroidandroid-manifest
Neeraj Verma
Neeraj Verma

Reputation: 2334

Attempt to invoke virtual method 'void android.app.ActionBar.setHomeButtonEnabled(boolean)' on a null object reference

I have seen other soution but i think my situation is diffrent . , I am trying to implement ActionBar with Tabs from this example ; http://www.androidgreeve.com/2014/01/android-actionbar-navigating-with-swipeable-tabs-and-views.html

on 

actionBar.setHomeButtonEnabled(false);

program throws error :

Attempt to invoke virtual method 'void android.app.ActionBar.setHomeButtonEnabled(boolean)' on a null object reference

here is the code

package com.example.administrator.fragmentsexample;

import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;

import com.example.administrator.adapter.TabsPagerAdapter;

public class MainActivity extends FragmentActivity implements
        ActionBar.TabListener {

    private ViewPager viewPager;
    private TabsPagerAdapter mAdapter;
    private ActionBar actionBar;
    // Tab titles
    private String[] tabs = {"Social", "Organizer", "Movies"};

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

        // Initilization
        viewPager = (ViewPager) findViewById(R.id.pager);
        actionBar = getSupportActionBar();
        mAdapter = new TabsPagerAdapter(getSupportFragmentManager());

        viewPager.setAdapter(mAdapter);
        actionBar.setHomeButtonEnabled(false);
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        // Adding Tabs
        for (String tab_name : tabs) {
            actionBar.addTab(actionBar.newTab().setText(tab_name)
                    .setTabListener(this));

        }
    }

    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {

    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {

    }

    @Override
    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {

    }
}

My Manifest File :

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.administrator.fragmentsexample" >

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

I tried to replace FragmentActivity with ActioBarActivity but it is shoing deprecated API Error i think I am missing very basic thing .. what am I missing in code ?

Upvotes: 4

Views: 7736

Answers (2)

Soham
Soham

Reputation: 4417

Change ActionBarAtivity to AppCompatActivity

Upvotes: -2

Rene M.
Rene M.

Reputation: 2690

FragmentActivity out of support.v4 is not including a SupportActionBar, this why you get Null Reference.

Change your class definition to extend AppCompatActivity which extends FragmentActivity like so:

public class MainActivity extends AppCompatActivity implements
        ActionBar.TabListener {
...
}

Change your Import of ActionBar to:

import android.support.v7.app.ActionBar

Because like the API Docs said: http://developer.android.com/reference/android/support/v7/app/AppCompatActivity.html#getSupportActionBar() It returns the support library version of the ActionBar impl. ;)

Attention! Regarding Deprecated mark on SupportActionBarActivity I changed extend to AppCompatActivity.

Thats all.

Upvotes: 3

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