Application

Base class for maintaining global application state. You can provide your own implementation by creating a subclass and specifying the fully-qualified name of this subclass as the "android:name" attribute in your AndroidManifest.xml's <application> tag. The Application class, or your subclass of the Application class, is instantiated before any other class when the process for your application/package is created.

用來維護全局應用狀態的基類，你可以通過創建子類併在AndroidManifest.xml的<application>標簽下的 "android:name" 屬性指定全限定類名來提供你自己的實現。Application類或者你自己創建的Application的子類，會在你的application/package的進程創建之前的任何類之前實例化。

Note: There is normally no need to subclass Application. In most situations, static singletons can provide the same functionality in a more modular way. If your singleton needs a global context (for example to register broadcast receivers), include Context.getApplicationContext() as a Context argument when invoking your singleton's getInstance() method.

註意：通常不太需要實現Application子類。在大多數情況下，靜態單例類會更模塊化地提供相同的功能。如果你的單例類需要全局的context（例如：要註冊broadcast receiver），當調用你單例類的getInstance()方法時，包含Context.getApplicationContext()作為Context。