java - activity crashes when going back home -

i have edit task activity single edittext view. when click button on action bar, database updated , log registers it, activity crashes while going back. main activity display text added in task activity. here code home button:

public class newtask extends activity { protected taskerdbhelper db; myadapter adapt;  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_new_task);     db = new taskerdbhelper(this);     setupactionbar(); }  private void setupactionbar() {      getactionbar().setdisplayhomeasupenabled(true);  }  @override public boolean oncreateoptionsmenu(menu menu) {     // inflate menu; adds items action bar if present.     getmenuinflater().inflate(r.menu.new_task, menu);     return true; }  @override public boolean onoptionsitemselected(menuitem item) {     switch (item.getitemid()) {     case android.r.id.home:         // id represents home or button. in case of         // activity, button shown. use navutils allow users         // navigate 1 level in application structure.         // more details, see navigation pattern on android design:         //         // http://developer.android.com/design/patterns/navigation.html#up-vs-back         //         edittext t = (edittext) findviewbyid(r.id.edittext1);         string s = t.gettext().tostring();         if (s.equalsignorecase("")) {             toast.maketext(this, "enter task description first!!",                     toast.length_long);         } else {             task task = new task(s, 0);             db.addtask(task);             log.d("tasker", "data added");             //t.settext("");             //adapt.add(task);             adapt.notifydatasetchanged();         }         setresult(result_ok);         finish();         return true;     }     return super.onoptionsitemselected(item); } 

}

whats wrong?

here log:

08-16 17:56:05.117: e/androidruntime(6162): fatal exception: main 08-16 17:56:05.117: e/androidruntime(6162): java.lang.nullpointerexception 08-16 17:56:05.117: e/androidruntime(6162):     @ com.example.tasker.newtask.onoptionsitemselected(newtask.java:62) 08-16 17:56:05.117: e/androidruntime(6162):     @ android.app.activity.onmenuitemselected(activity.java:2552) 08-16 17:56:05.117: e/androidruntime(6162):     @ com.android.internal.widget.actionbarview$3.onclick(actionbarview.java:167) 08-16 17:56:05.117: e/androidruntime(6162):     @ android.view.view.performclick(view.java:4204) 08-16 17:56:05.117: e/androidruntime(6162):     @ android.view.view$performclick.run(view.java:17355) 08-16 17:56:05.117: e/androidruntime(6162):     @ android.os.handler.handlecallback(handler.java:725) 08-16 17:56:05.117: e/androidruntime(6162):     @ android.os.handler.dispatchmessage(handler.java:92) 08-16 17:56:05.117: e/androidruntime(6162):     @ android.os.looper.loop(looper.java:137) 08-16 17:56:05.117: e/androidruntime(6162):     @ android.app.activitythread.main(activitythread.java:5234) 08-16 17:56:05.117: e/androidruntime(6162):     @ java.lang.reflect.method.invokenative(native method) 08-16 17:56:05.117: e/androidruntime(6162):     @ java.lang.reflect.method.invoke(method.java:525) 08-16 17:56:05.117: e/androidruntime(6162):     @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:799) 08-16 17:56:05.117: e/androidruntime(6162):     @ com.android.internal.os.zygoteinit.main(zygoteinit.java:566) 08-16 17:56:05.117: e/androidruntime(6162):     @ dalvik.system.nativestart.main(native method) 

try checking if adapter null first

if(adapt != null) {     adapt.notifydatasetchanged(); } else {    // initialize , other stuff } 

and in declaration, declare adapt this

public myadapter adapt; 

i can see using custom adapter class. think problem may there in notifydatasetchanged() method. can post it?