RelativeLayout layout attributes

Android: layout_above: place the bottom of the control on the control with the given ID
Android: layout_below: place the top of the control under the control with the given ID
Android: layout_toLeftOf align the right edge of the control with the left edge of the control with the given ID
Android: layout_toRightOf align the left edge of the control with the right edge of the control with the given ID
Android: layout_alignBaseline the baseline of the control is aligned with the baseline of the control with the given ID
Android: layout_alignBottom: Align the bottom edge of the control with the bottom edge of the given ID Control
Android: layout_alignLeft: Align the left edge of the control with the given ID
Android: layout_alignRight: Align the right edge of the control with the right edge of the given ID Control
Android: layout_alignTop: Align the top edge of the control with the top edge of the given ID Control
Android: layout_alignParentBottom if the value is true, the bottom of the control is aligned with the bottom of the parent control.
Android: layout_alignParentLeft if the value is true, the left edge of the control is aligned with the left edge of the parent control.
Android: layout_alignParentRight if the value is true, the right edge of the control is aligned with the right edge of the parent control.
Android: layout_alignParentTop if the value is true, the top of the control is aligned with the top of the parent control.
Android: layout_centerHorizontal if this value is true, the control will be placed in the center of the horizontal direction
Android: layout_centerInParent if the value is true, the control is placed in the center of both the horizontal and vertical directions of the parent control.
Android: layout_centerVertical if this value is true, the control will be placed in the center of the vertical direction
Author's "Android Learning Experience"