什么是Android上的“上下文"? [英] What is 'Context' on Android?

问题描述

在Android编程中，Context类的确切含义是什么?

In Android programming, what exactly is a Context class and what is it used for?

我在开发者网站上了解了此信息，但我无法清楚地了解它.

I read about it on the developer site, but I am unable to understand it clearly.

推荐答案

简单地将其放入:

顾名思义，它是应用程序/对象当前状态的上下文.它使新创建的对象了解正在发生的事情.通常，您调用它来获取有关程序另一部分(活动和程序包/应用程序)的信息.

As the name suggests, it's the context of current state of the application/object. It lets newly-created objects understand what has been going on. Typically you call it to get information regarding another part of your program (activity and package/application).

您可以通过调用getApplicationContext()，getContext()，getBaseContext()或this(在从Context扩展的类中，例如Application，Activity，Service和IntentService类)来获取上下文.

You can get the context by invoking getApplicationContext(), getContext(), getBaseContext() or this (when in a class that extends from Context, such as the Application, Activity, Service and IntentService classes).

上下文的典型用法:

• 创建新对象: 创建新的视图，适配器，侦听器:

• Creating new objects: Creating new views, adapters, listeners:

TextView tv = new TextView(getContext());
ListAdapter adapter = new SimpleCursorAdapter(getApplicationContext(), ...);

访问标准通用资源: 诸如LAYOUT_INFLATER_SERVICE，SharedPreferences之类的服务:

Accessing standard common resources: Services like LAYOUT_INFLATER_SERVICE, SharedPreferences:

context.getSystemService(LAYOUT_INFLATER_SERVICE)
getApplicationContext().getSharedPreferences(*name*, *mode*);

隐式访问组件: 关于内容提供商，广播，意图

Accessing components implicitly: Regarding content providers, broadcasts, intent

getApplicationContext().getContentResolver().query(uri, ...);

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