NullPointerException: with ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference

The cause of your issue is using 

MainActivity
extend Activity

 with support theme 

style
name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar"

. It's incompatible things. Which min sdk you need?In your code having 

MainActivity
extends Activity

 you don't need 

AppCompatTheme

.Use 

name="AppTheme"
parent="android:Theme.Light

"If you are using 

Theme.AppCompat.Light.DarkActionBar

,you should extend your 

Activity

 from 

AppCompatActivity

,and use 

getSupportActionBar()

.Instead of:

public class MainActivity extends Activity {

use:

public class MainActivity extends AppCompatActivity {

and instead of:

getActionBar().setTitle(mTitles);

use:

getSupportActionBar().setTitle(mTitles);