Android——View的一些属性

fill_parent：设置一个顶部布局或控件强制性让它布满整个屏幕。

wrap_content：布局指根据视图内部内容自动扩展以适应其大小。

the "wrap_content" value specifies that the view should be only as big as needed to fit the contents of the view. If you were to instead use"match_parent", then the EditText element would fill the screen, because it would match the size of the parent LinearLayout.