android - What is difference between custom dialog and activity as dialog means "Theme.Dialog"? -

here question real difference between custom dialog , activity made theme dialog , opening dialog, have used both of these, of small difference understand follows

1. coding remains in other file in activity , in same file in custom dialog(if haven't created new class file dialog),
2. activity stays in activity stack, while dialog not.

is there other difference? y need custom dialog in place of activity dialog , visa versa,

my current problem when click on listitem , opens new activity (as dialog here), , when press button , click again on item "stops unexpectedly", , couldn't understand error, error below

 04-18 12:21:18.945: e/androidruntime(915): fatal exception: main 04-18 12:21:18.945: e/androidruntime(915): java.lang.illegalstateexception: content of adapter has changed listview did not receive notification. make sure content of adapter not modified background thread, ui thread. [in listview(2131230777, class android.widget.listview) adapter(class com.logicbridge.lazyloader.myorderslazyadapter)] 04-18 12:21:18.945: e/androidruntime(915):  @ android.widget.listview.layoutchildren(listview.java:1538) 04-18 12:21:18.945: e/androidruntime(915):  @ android.widget.abslistview$checkfortap.run(abslistview.java:2728) 04-18 12:21:18.945: e/androidruntime(915):  @ android.os.handler.handlecallback(handler.java:605) 04-18 12:21:18.945: e/androidruntime(915):  @ android.os.handler.dispatchmessage(handler.java:92) 04-18 12:21:18.945: e/androidruntime(915):  @ android.os.looper.loop(looper.java:137) 04-18 12:21:18.945: e/androidruntime(915):  @ android.app.activitythread.main(activitythread.java:4424) 04-18 12:21:18.945: e/androidruntime(915):  @ java.lang.reflect.method.invokenative(native method) 04-18 12:21:18.945: e/androidruntime(915):  @ java.lang.reflect.method.invoke(method.java:511) 04-18 12:21:18.945: e/androidruntime(915):  @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:784) 04-18 12:21:18.945: e/androidruntime(915):  @ com.android.internal.os.zygoteinit.main(zygoteinit.java:551) 04-18 12:21:18.945: e/androidruntime(915):  @ dalvik.system.nativestart.main(native method) 

my code listview

@override     protected void oncreate(bundle savedinstancestate) {         // todo auto-generated method stub         super.oncreate(savedinstancestate);         setcontentview(r.layout.my_order_list);         initcontrols();         loadlist();     }      private void initcontrols() {         progress = new progressdialog(this);         progress.setmessage("loading...");         list = (listview) findviewbyid(r.id.my_order_list);      }      private void loadlist() {         staticitems.myorderadapter = new myorderslazyadapter(myorders.this,                 staticitems.myorderlistarr);         list.setadapter(staticitems.myorderadapter);         list.setonitemlongclicklistener(new onitemlongclicklistener() {              @override             public boolean onitemlongclick(adapterview<?> arg0, view arg1,                     int arg2, long arg3) {                 // todo auto-generated method stub                 // starts new activity after process                 arraylist<string> str = new arraylist<string>();                 str.add("loadordersdetail");                 str.add("2");                 new mytask(str).execute();                 return false;             }         });     } 

does happens because of have used new activity instead of dialog??

dialog , activity different things. example, service or broadcast receiver can start activity, cannot start dialog. in general, dialog belongs activity , activity controls lifecycle of dialog (ie: when created, shown, dismissed, etc.). note: can have dialog doesn't belong activity, special case.

there times when want show user looks dialog, need use activity that. example notification. sometimes, when user chooses notification notification bar, want show him dialog. can't start dialog notification. instead, use activity uses theme.dialog. activity behaves activity, user it looks dialog (ie: doesn't take entire screen, has transparent background user can see activity underneath it, etc.)