[Solved] java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity

Recently Android SDK released a new update, and when you create a new application it automaticaly imports a library named Appcompat, when you try to compile and run the App you get this error in LogCat

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.txt2lrn.www/com.txt2lrn.www.LandingActivity}:
 java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
 at android.app.ActivityThread.access$1500(ActivityThread.java:117)
 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
 at android.os.Handler.dispatchMessage(Handler.java:99)
 at android.os.Looper.loop(Looper.java:130)
 at android.app.ActivityThread.main(ActivityThread.java:3687)
 at java.lang.reflect.Method.invokeNative(Native Method)
 at java.lang.reflect.Method.invoke(Method.java:507)