How to Use the actionbar in the V7 package

================================= Problem description ========================== =
I strictly follow the steps of the android official website to import the android-support-v7-appcompat library project, and then create a new project, introduce this library project, compilation is no problem.
However, the following problems are reported during the migration,

Java. Lang. runtimeexception: unable to start activity componentinfo {com. example. actionbarlower/COM. example. actionbarlower. mainactivity}: Java. Lang. nullpointerexception
At Android. App. activitythread. javasmlaunchactivity (activitythread. Java: 2295)
At Android. App. activitythread. handlelaunchactivity (activitythread. Java: 2349)
At Android. App. activitythread. Access $700 (activitythread. Java: 159)
At Android. App. activitythread $ H. handlemessage (activitythread. Java: 1316)
At Android. OS. handler. dispatchmessage (handler. Java: 99)
At Android. OS. lorule. Loop (lorule. Java: 176)
At Android. App. activitythread. Main (activitythread. Java: 5419)
At java. Lang. Reflect. method. invokenative (native method)
At java. Lang. Reflect. method. Invoke (method. Java: 525)
At com. Android. Internal. OS. zygoteinit $ methodandargscaller. Run (zygoteinit. Java: 1209)
At com. Android. Internal. OS. zygoteinit. Main (zygoteinit. Java: 1025)
At Dalvik. system. nativestart. Main (native method)
Caused by: Java. Lang. nullpointerexception
At Android. Support. v7.app. actionbarimplics. setdisplayshowhomeenabled (actionbarimplics. Java: 169)
At Android. Support. v7.app. actionbarimpljb. setdisplayshowhomeenabled (actionbarimpljb. Java: 20)
At com. example. actionbarlower. mainactivity. oncreate (mainactivity. Java: 20)
At Android. App. activity. javasmcreate (activity. Java: 5372)
At Android. App. instrumentation. callactivityoncreate (instrumentation. Java: 1104)
At Android. App. activitythread. javasmlaunchactivity (activitythread. Java: 2257)
... 11 more

The Code is as follows:
Public class mainactivity extends actionbaractivity {

Private actionbar supportactionbar;

@ Override
Protected void oncreate (bundle savedinstancestate ){
Super. oncreate (savedinstancestate );
Setcontentview (R. layout. activity_main );

Supportactionbar = getsuppactionactionbar ();
Supportactionbar. setdisplayshowhomeenabled (true );

}

@ Override
Public Boolean oncreateoptionsmenu (menu ){
Getmenuinflater (). Inflate (R. Menu. Main, menu );
Return super. oncreateoptionsmenu (menu );
}

}


Manifest is as follows:

<? XML version = "1.0" encoding = "UTF-8"?>
<Manifest xmlns: Android = "http://schemas.android.com/apk/res/android"
Package = "com. example. actionbarlower"
Android: versioncode = "1"
Android: versionname = "1.0" type = "codeph" text = "/codeph">

<Uses-SDK
Android: minsdkversion = "8"
Android: targetsdkversion = "9"/>

<Application
Android: allowbackup = "true"
Android: icon = "@ drawable/ic_launcher"
Android: Label = "@ string/app_name"
Android: theme = "@ style/apptheme">
<Activity
Android: Name = "com. example. actionbarlower. mainactivity"
Android: Label = "@ string/app_name"
Android: theme = "@ style/theme. appcompat. Light">
<Intent-filter>
<Action Android: Name = "android. Intent. Action. Main"/>

<Category Android: Name = "android. Intent. Category. launcher"/>
</Intent-filter>
</Activity>
</Application>

</Manifest>



The Null Pointer Points to supportactionbar. setdisplayshowhomeenabled (true); this line, but it is not empty to print suppactionactionbar in front.

=============================== Solution 1 ========================== ===
Android: minsdkversion and Android: targetsdkversion are changed to 10 and 15 respectively.

How to Use the actionbar in the V7 package