java - Where to place setContentView() in onCreate()? -


i beginner in android , want know why when place setcontentview() after defining textview, app crashes, i.e

protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     textview tv=(textview) findviewbyid(r.id.tv);     linkify.addlinks(tv, linkify.web_urls|linkify.email_addresses|             linkify.phone_numbers);     setcontentview(r.layout.activity_main);     //after textview  }

but when put setcontentview() before defining textview app runs fine. 

protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);   //before textview     textview tv=(textview) findviewbyid(r.id.tv);     linkify.addlinks(tv, linkify.web_urls|linkify.email_addresses|             linkify.phone_numbers); }

why & , how adding setcontentview() before makes difference ?

setcontentview() literally sets views of activity. if try textview tv=(textview) findviewbyid(r.id.tv);, there no view find because haven't set views yet, , app crashes. why should put setcontentview() before try access views.


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