關於layout_weight屬性，以layout_width爲例：
當layout_width爲fill_parent時，對於一個組件，該組件相對於其它組件的layout_weight值越小時，它的寬度相對於其它組件越大。但最大不超過fill_parent。
當layout_width爲wrap_content時，對於一個組件，該組件相對於其它組件的layout_weight值越小時，它的寬度相對於其它組件越小。但最小不小於wrap_content。
layout_height類似。
android官方文檔：
layout_weight is used in LinearLayouts to assign "importance" to Views within the layout. All Views have a default layout_weight of zero, meaning they take up only as much room on the screen as they need to be displayed. Assigning a value higher than zero will split up the rest of the available space in the parent View, according to the value of each View's layout_weight and its ratio to the overalllayout_weight specified in the current layout for this and other View elements.