android - Why am I not able to change the title of my action bar? -

i tried change title of action bar using tips given in other answers don't seem work.i trying change title "test".

here activity_detectlayout.xml

<relativelayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingleft="@dimen/activity_horizontal_margin" android:paddingright="@dimen/activity_horizontal_margin" android:paddingtop="@dimen/activity_vertical_margin" android:paddingbottom="@dimen/activity_vertical_margin" tools:context="com.kaushik.abhishek.facedetecto.detectlayout">   <imageview     android:layout_width="fill_parent"     android:layout_height="fill_parent"     android:id="@+id/image_view"     android:layout_weight="1.0"     android:layout_alignparenttop="true"     android:layout_alignparentright="true"     android:layout_alignparentend="true" />  <button     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:id="@+id/detect_face"     android:text="@string/detect_face"     android:layout_gravity="center_horizontal"     android:layout_alignparentbottom="true"     android:layout_alignparentright="true"     android:layout_alignparentend="true"     android:layout_alignparentleft="true"     android:layout_alignparentstart="true"     android:background="#d4424646"     android:textcolor="#fdfffa" /> 

detectlayout.java

package com.kaushik.abhishek.facedetecto;  import android.support.v7.app.appcompatactivity; import android.os.bundle; import android.view.menu; import android.view.menuitem;  public class detectlayout extends appcompatactivity {  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     getactionbar().settitle("test");     setcontentview(r.layout.activity_detectlayout); }  @override public boolean oncreateoptionsmenu(menu menu) {     // inflate menu; adds items action bar if present.     getmenuinflater().inflate(r.menu.menu_detectlayout, menu);     return true;  }  @override public boolean onoptionsitemselected(menuitem item) {     // handle action bar item clicks here. action bar     // automatically handle clicks on home/up button, long     // specify parent activity in androidmanifest.xml.     int id = item.getitemid();      //noinspection simplifiableifstatement     if (id == r.id.action_settings) {         return true;     }      return super.onoptionsitemselected(item); } } 

the manifest file

<?xml version="1.0" encoding="utf-8"?> 

<uses-sdk     android:minsdkversion="8"     android:targetsdkversion="15" /> <uses-permission android:name="android.permission.write_external_storage"/> <uses-permission android:name="android.permission.camera"/>  <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>     <activity         android:name=".detectlayout"         android:label="@string/title_activity_detectlayout" >     </activity> </application> 

styles.xml

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

use on activity inside oncreate method.

    getsupportactionbar().setdisplayhomeasupenabled(true);     getsupportactionbar().settitle("your title"); 

or, change menifest

       <activity         android:name=".youractivity"         android:label="your title" />