What is wrong with this use of Application context in Android? -

i abstract model this:first there class userinfo holds user information:

public class userinfo extends application{ private int userid; public void setuserid(int id) {     userid=id; } public int  getuserid() {     return userid; }  } 

then in mainactivity:

 @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     ...     userinfo=(userinfo)getapplication();     userinfo.setuserid(1354);     ....     intent intent=new intent(mainactivity.this,voteactivity.class);                                  startactivity(intent); } public @override void onresume() {     super.onresume();     textview text=(textview)mainactivity.this.findviewbyid(r.id.usernametext);     text.settext(userinfo.getuserid()+" "); } 

and in voteactivity:

@override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_vote);             userinfo=(userinfo)getapplication();      button back=(button)findviewbyid(r.id.backbutton);     back.setonclicklistener(new onclicklistener(){          @override         public void onclick(view arg0) {             userinfo.setuserid(-100);             intent intent=new        intent(voteactivity.this,mainactivity.class);             startactivity(intent);          }});  } 

the result is: when mainactivity first run, userid in userinfo 1354 ; , when voteactivity first run, userid in userinfo 1354 too.however when mainactivity voteacitivy userid remains 1354 should -100.what wrong use of application context?

you're starting new activity in onclick method :

intent intent=new        intent(voteactivity.this,mainactivity.class);         startactivity(intent); 

and direct set id in mainactivity :

 userinfo.setuserid(1354); 

that's why (1354). should call finish in on click (instead of starting mainactivity).

the activity's stack : mainactivity - voteactivity - mainactivity , think want : mainactivity after pressed on button

@override         public void onclick(view arg0) {             userinfo.setuserid(-100);             finish();          }});