Before understanding ViewRoot, DecorView & Window, look at the structure View of chromatography.
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DecorView as the topmost Window View entire interface.
DecorView only one child is LinearLayout. Representative of the Window interface, includes the notification bar, title bar, display the contents of three bar area.
There are two LinearLayout FrameLayout children.
(20) for the title bar display. Only a TextView display application
(21) for the content bar display. It is the setContentView () method of loading a layout interface, added thereto.

A .VeiwRoot

1 Introduction

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2 Special Note:

// 在主线程中，Activity对象被创建后：
// 1. 自动将DecorView添加到Window中 & 创建ViewRootImpll对象
root = new ViewRootImpl(view.getContent(),display);

// 3. 将ViewRootImpll对象与DecorView建立关联
root.setView(view,wparams,panelParentView)

Two .DecorView

1. Definitions

Top View, i.e. the root node of the tree view Android; FrameLayout also the subclass.

2. Role

Load & display layout. Event View layers have to go through DecorView, and then passed to the View.

3. Special Note

Containing a vertical direction LinearLayout, divided into two parts:
= title bar (TitleBar) (1)
(2) = content column (content)

Here Insert Picture Description In Activity by setContentView () into the layout file set is actually being added to the contents column, becoming the only son View = id for the content of FrameLayout in.

NOTE: Get setContentView () View code is provided as follows:

// 在代码中可通过content得到对应加载的布局

// 1. 得到content
ViewGroup content = (ViewGroup)findViewById(android.R.id.content);
// 2. 得到设置的View
ViewGroup rootView = (ViewGroup) content.getChildAt(0);