android - Null Point exception -

android - Null Point exception -

i'm new android app development.i have developed basic app , found null point error @ particular line , added if(instance!=null){do something} .but part within if i.e, part never executed.how can prepare this? app works property

package com.example.first;

import android.support.v7.app.actionbaractivity; import android.support.v4.app.fragment; import android.os.bundle; import android.util.log; import android.view.layoutinflater; import android.view.menu; import android.view.menuitem; import android.view.view; import android.view.view.onclicklistener; import android.view.viewgroup; import android.widget.button; import android.widget.imageview;

public class mainactivity extends actionbaractivity { private button btn1;

private imageview imagetoshow; @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main);

btn1=(button)findviewbyid(r.id.button1); imagetoshow=(imageview)findviewbyid(r.id.imageview1); if(btn1!=null){ btn1.setonclicklistener(new view.onclicklistener() { @override public void onclick(view v) { imagetoshow.setimageresource(r.drawable.image1); } }); } if (savedinstancestate == null) { getsupportfragmentmanager().begintransaction() .add(r.id.container, new placeholderfragment()) .commit(); } } @override public boolean oncreateoptionsmenu(menu menu) { // inflate menu; adds items action bar if present. getmenuinflater().inflate(r.menu.main, menu); homecoming true; } @override public boolean onoptionsitemselected(menuitem item) { // handle action bar item clicks here. action bar // automatically handle clicks on home/up button, long // specify parent activity in androidmanifest.xml. int id = item.getitemid(); if (id == r.id.action_settings) { homecoming true; } homecoming super.onoptionsitemselected(item); } /** * placeholder fragment containing simple view. */ public static class placeholderfragment extends fragment { public placeholderfragment() { } @override public view oncreateview(layoutinflater inflater, viewgroup container, bundle savedinstancestate) { view rootview = inflater.inflate(r.layout.fragment_main, container, false); homecoming rootview; } }

}

the code isn't beingness executed because if (instance != null) statement isn't true. if want code run, , don't want have nullpointerexception initialise whichever variable null (i.e. give value). @ point can remove null check no longer needed.

post code if want more detailed answer.

android