try this
activity which has the Theme.Dialog style set, do this:
@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);
setContentView(R.layout.your_layout);
getWindow().setLayout(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT); }

In your activity which has the Theme.Dialog style set, do this:
@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.your_layout); getWindow().setLayout(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT); }