Problem showing an Activity as Dialog without Title & as an Activity too

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Hello,
I have an Activity (ExpandListActivity) which in one cas want to show as a Dialog and in other situation want to show as an Activity. The layout of ExpandListActivity has a TextView & ExpandList in a LinearLayout. When I show it as Dialog I want to remove the TitleBar & TextView from the layout, otherwise want both of them.
I tried setting Theme of ExpandListActivity as Dialog in manifest file, but then am not able to set the theme back to normal when am showing it as an Activity.
I removed Dialog Theme from manifest, and added requestWindowFeature (Window.FEATURE_NO_TITLE);, for the Dialog case, this gives me RuntimeException on this line. Added code to remove the TextView, but that also doesn't work.
My code is as follows :
ExpandListActivity is the Activity that I want to call as a Dialog &/or as an Activity :

@Overridepublic void onCreate(Bundle savedInstanceState) { 
Intent sender = getIntent();
boolean fDialogMode = sender.getBooleanExtra("dialogMode", false);
Log.i("ELA", "For Dialog : " + fDialogMode);
/* 
// If in Dialog mode, 
if (fDialogMode) {
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
} else {
super.setTheme(android.R.style.Theme);
}*/

super.onCreate(savedInstanceState);
//setContentView(R.layout.expand_list_layout);
//TextView tv = (TextView) findViewById(R.id.expandListTitle);
if (fDialogMode) {
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.expand_list_layout); 
} else {
ViewGroup vg = (ViewGroup) findViewById(R.id.lldata);
//vg.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
ViewGroup.inflate(ExpandListActivity.this, R.layout.expand_list_layout, vg);
//TextView tv = (TextView) vg.findViewById(R.id.expandListTitle);
//tv.setText("Helpline");
}

Activity from which I call it as an Activity :

Intent intent1 = null;
intent1 = new Intent(Mumbai77Activity.this, HelplineActivity.class);
intent1.putExtra("dialogMode", false);
intent1.putStringArrayListExtra("lines", lines);

startActivity(intent1);

Activity from which I call it as a Dialog :

Intent intent1 =new Intent(PincodesActivity.this, ExpandListActivity.class);

intent1.putExtra("dialogMode", true);
intent1.putStringArrayListExtra("lines", lines);

startActivity(intent1);

Can anyone help me out with this problem. Am stuck from 2 days with this problem. Any help is highly appreciated. I am new in this forum, not used to posting code here, so maybe some code is not in proepr format.
Thanks