使用AlertDialog报错 You need to use a Theme.AppCompat theme (or descendant) with this activity.之解决

以前由于继承自ActionBarActivity用得好好的，现在直接继承Activity，使用AlertDialog，则会报以下这个错误：

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

 

可以这样解决
http://anforen.com/wp/2016/04/alertdialog-java-lang-illegalstateexception-you-need-to-use-a-theme-appcompat-theme-or-descendant-with-this-activity/