Strictly speaking android:gravity is not a Layout Param. The android:gravity is really an attribute of the View Group. It controls the way the contents of the View Group will be positioned horizontally and vertically. android:layout_gravity Layout Param The android:layout_gravity is a Layout Param. Not all View Groups support this Layout Param. See the documentation to find out which Layout Params are supported by a particular View Group. Linear Layout does support android:layout_gravity Layout Param. For a horizontal Linear Layout the following values make sense: * top * center * bottom That is because the children of a horizontal Linear Layout are layed out horizontally one after the other. Only thing can be controlled using the android:layout_gravity is how a child view is positioned vertically. In the above example the top Linear Layout is a horizontal Linear Layout. Setting the android:layout_gravity=top on the l_g=top Button has an effect of positioning it at the top. Setting the android:layout_gravity=center on the l_g=center Button has an effect of positioning it at the vertical center. Setting the android:layout_gravity=bottom on the l_g=bottom Button has an effect of positioning it at the bottom. For a vertical Linear Layout the following values make sense: * left * center * right That is because the children of a vertical Linear Layout are layed out vertically one below the other. Only thing can be controlled using the android:layout_gravity is how a child view is positioned horizontally. In the about example the bottom Linear Layout is a vertical Linear Layout. Setting the android:layout_gravity=left on the l_g=left Button has an effect of positioning it at the left. Setting the android:layout_gravity=center on the l_g=center Button has an effect of positioning it at the horizontal center. Setting the android:layout_gravity=right on the l_g=right Button has an effect of positioning it at the right.
