[안드로이드] Fragment 에서 Toast 사용하기

출처: https://stackoverflow.com/questions/20261181/nullpointerexception-on-getactivity-fragment

1. First declare context variable: 
   private Context context;
2. In onCreateView():
   context = container.getContext();
3. Use it for Toast:
   Toast.makeText(context, "Your vote was sent", Toast.LENGTH_LONG).show();