Trying to call the virtual method 'void android.app.ActionBar.setHomeButtonEnabled (boolean)' on a null object reference
I saw a different soution, but I think my situation is different. I am trying to implement a Tabbed ActionBar from this example; http://www.androidgreeve.com/2014/01/android-actionbar-navigating-with-swipeable-tabs-and-views.html
on
actionBar.setHomeButtonEnabled(false);
the program gives an error:
Trying to call virtual method 'void android.app.ActionBar.setHomeButtonEnabled (boolean)' on 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 threw a deprecated API error I think I am missing the main thing. What am I missing in the code?
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The FragmentActivity from support.v4 doesn't include the SupportActionBar, so you get a Null Reference.
Modify the class definition to extend AppCompatActivity, which extends FragmentActivity as follows:
public class MainActivity extends AppCompatActivity implements
ActionBar.TabListener {
...
}
Change your ActionBar import to:
import android.support.v7.app.ActionBar
Since the API Docs said: http://developer.android.com/reference/android/support/v7/app/AppCompatActivity.html#getSupportActionBar () It returns the ActionBar support library version impl .;)
Attention! Regarding the deprecated label in SupportActionBarActivity, I changed it to AppCompatActivity.
That's all.
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