Android gravity屬性詳解（註：此屬性是linearlayout的屬性）

Value	Description
top	Put the object at the top of its container, not changing its size. 將對象放在其容器的頂部，不改變其大小.
bottom	Put the object at the bottom of its container, not changing its size. 將對象放在其容器的底部，不改變其大小.
left	Put the object at the left edge of its container, not changing its size. 將對象放在其容器的左側，不改變其大小.
right	Put the object at the right edge of its container, not changing its size. 將對象放在其容器的右側，不改變其大小.
center_vertical	Place object in the vertical center of its container, not changing its size. 將對象縱向置中，不改變其大小. 垂直對齊：垂直方向上置中對齊。
fill_vertical	Grow the vertical size of the object if needed so it completely fills its container. 必要的時候增加對象的縱向大小，以完全充滿其容器. 垂直方向填充
center_horizontal	Place object in the horizontal center of its container, not changing its size. 將對象橫向置中，不改變其大小. 水平對齊：水平方向上置中對齊
fill_horizontal	Grow the horizontal size of the object if needed so it completely fills its container. 必要的時候增加對象的橫向大小，以完全充滿其容器. 水平方向填充
center	Place the object in the center of its container in both the vertical and horizontal axis, not changing its size. 將對象橫縱置中，不改變其大小.
fill	Grow the horizontal and vertical size of the object if needed so it completely fills its container. This is the default. 必要的時候增加對象的橫縱向大小，以完全充滿其容器.
clip_vertical	Additional option that can be set to have the top and/or bottom edges of the child clipped to its container's bounds. The clip is based on the vertical gravity: a top gravity clips the bottom edge, a bottom gravity clips the top edge, and neither clips both edges. 附加選項，用於按照容器的邊來剪下對象的頂部和/或底部的內容. 剪下基於其縱向對齊設定：頂部對齊時，剪下底部；底部對齊時剪下頂部；除此之外剪下頂部和底部. 垂直方向裁剪
clip_horizontal	Additional option that can be set to have the left and/or right edges of the child clipped to its container's bounds. The clip is based on the horizontal gravity: a left gravity clips the right edge, a right gravity clips the left edge, and neither clips both edges. 附加選項，用於按照容器的邊來剪下對象的左側和/或右側的內容. 剪下基於其橫向對齊設定：左側對齊時，剪下右側；右側對齊時剪下左側；除此之外剪下左側和右側. 水平方向裁剪