As Android Document says Subclass of RelativeLayout that supports percentage based dimensions and margins. You can specify dimension or a margin of child by using attributes with "Percent" suffix.
It is not necessary to specify layout_width/height if you specify layout_widthPercent. However, if you want the view to be able to take up more space than what percentage value permits, you can add layout_width/height="wrap_content". In that case if the percentage size is too small for the View's content, it will be resized using wrap_content rule.
