relLayoutParams.alignWithParent=true
RelativeLayout.CENTER_HORIZONTAL
RelativeLayout.CENTER_VERTICAL
RelativeLayout.CENTER_IN_PARENT
RelativeLayout.ALIGN_PARENT_BOTTOM
RelativeLayout.ALIGN_PARENT_TOP
RelativeLayout.ALIGN_PARENT_LEFT 紧贴父控件的左边边缘
RelativeLayout.ALIGN_PARENT_RIGHT
RelativeLayout.ABOVE
RelativeLayout.BELOW
RelativeLayout.LEFT_OF
RelativeLayout.RIGHT_OF
RelativeLayout.ALIGN_TOP
RelativeLayout.ALIGN_BOTTOM
RelativeLayout.ALIGN_LEFT
RelativeLayout.ALIGN_RIGHT
RelativeLayout.ALIGN_BASELINE