I have an activity, that has in manifest:
android:theme="@android:style/Theme.Dialog"
When I start it, it looks like an activity, but when I close it it fires the onResume on the activity that started it. A real dialog will not do it. How can I avoid the onResume?
You can't - it's an activity. You could add some state machine to the calling activity using onPause etc. but that could get messy.