Layout入门

最新推荐文章于 2025-08-14 10:16:47 发布

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最新推荐文章于 2025-08-14 10:16:47 发布

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文章标签：移动开发 ui runtime

原文链接：http://www.cnblogs.com/darknife/archive/2013/04/30/3052481.html

本博阐述了布局（layout）在定义用户界面（如活动或应用小部件）的可视化结构方面的作用，介绍了如何在XML中声明布局以及如何在运行时实例化布局元素。每个布局文件必须包含一个根元素，可以是View或ViewGroup对象，通过添加更多的布局对象或小部件构建视图层次结构。

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A layout defines the visual structure for a user interface, such as the UI for an activity or app widget. You can declare a layout in two ways:

Declare UI elements in XML. Android provides a straightforward XML vocabulary that corresponds to the View classes and subclasses, such as those for widgets and layouts.
Instantiate layout elements at runtime. Your application can create View and ViewGroup objects (and manipulate their properties) programmatically.

　　Each layout file must contain exactly one root element, which must be a View or ViewGroup object. Once you've defined the root element, you can add additional layout objects or widgets as child elements to gradually build a View hierarchy that defines your layout.

layout为用户接口定义一个可视化的结构，比如activity或者appt widget的用户接口。

每一个个layout文件必须含有一个(只能是一个)View 或者 ViewGroup对象的root element。(在疯狂android讲义里说过：每一个Layout都是ViewGroup对象)你可以增加额外的layout对象（这个layout对象也至少有一个root element)或者widgets作为child element。

layout的继承图: