I've updated the API 21, tools and extras up to date, the ActionBar in some projects has gone invisible. I did this following code, but app crashes showing NullPointerException.

```
ActionBar actionBar = getActionBar();
actionBar.show();

```

Logcat Output

> 
> 02-23 18:03:36.269: E/AndroidRuntime(3327): FATAL EXCEPTION: main
>  02-23 18:03:36.269: E/AndroidRuntime(3327): Process: com.example.twaapp, PID: 3327
>  02-23 18:03:36.269: E/AndroidRuntime(3327): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.twaapp/com.example.twaapp.MainActivity}: java.lang.NullPointerException
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2198)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2257)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at android.app.ActivityThread.access$800(ActivityThread.java:139)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at android.os.Handler.dispatchMessage(Handler.java:102)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at android.os.Looper.loop(Looper.java:136)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at android.app.ActivityThread.main(ActivityThread.java:5086)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at java.lang.reflect.Method.invokeNative(Native Method)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at java.lang.reflect.Method.invoke(Method.java:515)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at dalvik.system.NativeStart.main(Native Method)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): Caused by: java.lang.NullPointerException
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at com.example.twaapp.MainActivity.onCreate(MainActivity.java:82)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at android.app.Activity.performCreate(Activity.java:5248)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1110)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2162)
>  02-23 18:03:36.269: E/AndroidRuntime(3327): ... 11 more
> 
> 
> 

How to make AB visible?