To make this work, in addition to setting android:layout_width (for rows) or
android:layout_height (for columns), you must also set android:layout_weight.
This property indicates what proportion of the free space should go to that widget. If
you set android:layout_weight to be the same non-zero value for a pair of widgets
(e.g., 1), the free space will be split evenly between them. If you set it to be 1 for one
widget and 2 for another widget, the second widget will use up twice the free space
that the first widget does. And so on.