why null value display in actionbar in android? -

i making simple demo of tab view .but on first line getting null pointer exception . getting null value method getactionbar() why ? share class

import android.app.actionbar; import android.app.fragmenttransaction; import android.os.bundle; import android.support.v4.app.fragmentactivity;  public class mainactivity extends fragmentactivity implements actionbar.tablistener {    actionbar actionbar;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);         actionbar=getactionbar(); /// <- line causing issue         actionbar.setnavigationmode(actionbar.navigation_mode_tabs);     }     // ---------- methods ---------------// } 

i null value on line actionbar=getactionbar();

here manifest file , style.xml

<resources>      <!-- base application theme. -->     <style name="apptheme" parent="theme.appcompat.light">         <!-- customize theme here. -->     </style>  </resources> 

app.grudle

apply plugin: 'com.android.application'  android {     compilesdkversion 22     buildtoolsversion "22.0.1"      defaultconfig {         applicationid "com.example.naveen.tabviewswipe"         minsdkversion 15         targetsdkversion 22         versioncode 1         versionname "1.0"     }     buildtypes {         release {             minifyenabled false             proguardfiles getdefaultproguardfile('proguard-android.txt'), 'proguard-rules.pro'         }     } }  dependencies {     compile filetree(dir: 'libs', include: ['*.jar'])     compile 'com.android.support:appcompat-v7:22.2.1' } 

if want extend fragmentactivity, need use non-appcompat theme i.e. holo actionbar

<!-- base application theme. --> <style name="apptheme" parent="android:theme.holo">     <!-- customize theme here. --> </style>