What is ActionBar.setHomeButtonEnabled(boolean)

Question

I want to create a viewpager which contains 2 tabs, I have 3 layout:

This is activity_chart.xml that contains paper:

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
</android.support.v4.view.ViewPager>

This is AccountsActivityChart.java:

import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;

import com.rastari.salar.mymetarialbank.R;
import com.rastari.salar.mymetarialbank.adapter.TabsPagerAdapter;

/**
 * Created by Salar on 9/5/2015.
 */
public class AccountsActivityChart extends FragmentActivity implements ActionBar.TabListener {

    private ViewPager viewPager;
    private TabsPagerAdapter mAdapter;
    private ActionBar actionBar;
    // Tab titles
    private String[] tabs = { "Accounts Activity", "Chart Activity" };

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

        // Initilization
        viewPager = (ViewPager) findViewById(R.id.pager);
        actionBar = getActionBar();
        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));
        }

        /**
         * on swiping the viewpager make respective tab selected
         * */
        viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

            @Override
            public void onPageSelected(int position) {
                // on changing the page
                // make respected tab selected
                actionBar.setSelectedNavigationItem(position);
            }

            @Override
            public void onPageScrolled(int arg0, float arg1, int arg2) {
            }

            @Override
            public void onPageScrollStateChanged(int arg0) {
            }
        });
    }

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

    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
        // on tab selected
        // show respected fragment view
        viewPager.setCurrentItem(tab.getPosition());
    }

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

this is TabsPagerAdapter.java class:

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;


/**
 * Created by Salar on 26/4/2015.
 */
public class TabsPagerAdapter extends FragmentPagerAdapter {
    public TabsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int index) {

        switch (index) {
            case 0:
                // Accounts Activity fragment activity
                return new AccountsActivityFragment();
            case 1:
                // Chart Activity activity
                return new ChartActivityFragment();
        }
        return null;
    }

    @Override
    public int getCount() {
        // get item count - equal to number of tabs
        return 2;
    }

}

this is AccountsActivityFragment.java:

import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.rastari.salar.mymetarialbank.R;

/**
 * Created by Salar on 25/4/2015.
 */
public class AccountsActivityFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_accounts_activity, container, false);

        return rootView;
    }
}

this is ChartActivityFragment.java:

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.rastari.salar.mymetarialbank.R;

/**
 * Created by Salar on 9/5/2015.
 */
public class ChartActivityFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_chart_activity, container, false);

        return rootView;
    }
}

this is manifest:

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

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

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

</manifest>

When I run the app I get this Error:

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

How can I fix this?

could you please post your manifest too? to be more specific kindly say the theme you are using for the activity.. — Lal, May 10 '15 at 18:20
As per your question here is your answer http://developer.android.com/reference/android/app/ActionBar.html#setHomeButtonEnabled(boolean) — silverFoxA, May 10 '15 at 18:56
i figured anyway i hope you got your answer to the question you have asked — silverFoxA, May 10 '15 at 19:35

score 0 · Answer 1 · answered Jan 30 '17 at 08:52

I think you have applied the theme which is having no action bar. This is why when you are getting the actionbar instance, it will be null and you are calling the setHomeButtonEnabled on on the null actionbar instance. That is why you are getting the error.

Kyaw Soe Win · Answer 2 · 2015-05-10T18:25:12.787

-1

try actionBar = getSupportActionBar(); instead of actionBar = getActionBar();

edited May 10 '15 at 18:25

answered May 10 '15 at 18:20

Kyaw Soe Win

9
3

@Lal Developer can comment on another question needs 50 reputation.So, let them give try – Noorul Jan 30 '17 at 09:09

What is ActionBar.setHomeButtonEnabled(boolean)

2 Answers2