title: In android layouts what is the effect/meaning of layout_height="0dip"
body: <p>I've seen several examples that use
  android:layout_height="0px" or "0dip" but i do not understand the impact of this. It seems that would make the layout 0 pixels tall. Is the value mitigated but some other factor like 'weight' or the height of any parent views?</p>