Help java.lang.nullpointer exception

[android question]

I am an android beginner, created my project using api level 11 in android studio.I want to customize the action bar but if i perform any method it is showing errors like R can not be resolved
setContentView(R.layout.activity_main);

ActionBar ab=getActionBar();
ab.setHomeButtonEnabled(true);
Method invocation may produce java.lang.nullpointer exception
Please help me.

 

[The_Chief]

This is clearly a developer question. You are welcome to register and ask away in the Application Development Forum, where other developers can help you.