java - Menu does not show up in Android studio -

this androidmanifest

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"     package="k.coursera.mylocation">      <uses-permission android:name="android.permission.internet" />      <application         android:allowbackup="true"         android:icon="@mipmap/ic_launcher"         android:label="@string/app_name"         android:supportsrtl="true"         android:theme="@style/apptheme">         <activity android:name=".mainactivity">             <intent-filter>                 <action android:name="android.intent.action.main" />                   <category android:name="android.intent.category.launcher" />             </intent-filter>         </activity>         <activity android:name=".test"></activity>     </application>     </manifest> 

when tried change theme to:

android:theme="@style/themeoverlay.appcompat.actionbar" 

the menu show other function of act wouldn't work (such start new activity).

and here piece of code menu xml file:

<?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android">     <item android:id="@+id/deletecountry" android:title="delete" /> </menu> 

and java code:

@override public boolean oncreateoptionsmenu(menu menu) {     menuinflater inflater = getmenuinflater();     inflater.inflate(r.menu.main, menu);     return super.oncreateoptionsmenu(menu); }  @override public boolean onoptionsitemselected(menuitem item) {         switch (item.getitemid()) {         case r.id.deletecountry:             madapter.removeall();             return true;         default:             return super.onoptionsitemselected(item);       } }