Context

Context字面意思上下文，位于framework package的android.content.Context中，其实该类为LONG型，类似Win32中的Handle句柄.

Context提供了关于应用环境全局信息的接口。它是一个抽象类，它的执行被Android系统所提供。它允许获取以应用为特征的资源和类型。同时启动应用级的操作，如启动Activity，broadcasting和接收intents。

实现Context的类主要有Android特有的几个模型，Activity、Service以及BroadcastReceiver。

在android中context可以作很多操作，但是最主要的功能是加载和访问资源。在android中有两种context，一种是 application context，一种是activity context，通常我们在各种类和方法间传递的是activity context。

 

下面介绍Context的一些get方法，通过这些get方法可以获取应用环境全局信息：

 

1.public abstract Context getApplicationContext ()

Return the context of the single, global Application object of the current process.

2.public abstract ApplicationInfo getApplicationInfo ()

Return the full application info for this context's package.

3.public abstract ContentResolver getContentResolver ()

Return a ContentResolver instance for your application's package.

4.public abstract PackageManager getPackageManager ()

Return PackageManager instance to find global package information.

5.public abstract String getPackageName ()

Return the name of this application's package.

6.public abstract Resources getResources ()

Return a Resources instance for your application's package.

7.public abstract SharedPreferences getSharedPreferences (String name, int mode)

Retrieve and hold the contents of the preferences file 'name', returning a SharedPreferences through which you can retrieve and modify its values. Only one instance of the SharedPreferences object is returned to any callers for the same name, meaning they will see each other's edits as soon as they are made.

8.public final String getString (int resId)

Return a localized string from the application's package's default string table.

9.public abstract Object getSystemService (String name)

Return the handle to a system-level service by name. The class of the returned object varies by the requested name. Currently available names are: