英语原文 Android Application Fundamentals Android applications are written in the Java programming language. The Android SDK tools compile the code—along with any data and resource files—into an Android package, an archive file with an .apk suffix. All the code in a single .apk file is considered to application and is the file that Android-powered devices use to install the applicatio Once installed on a device, each Android application lives in its own security san The Android operating system is a multi-user Linux system in which each application is a different user. By default, the system assigns each application a unique Linux user ID (the ID used only by the system and is unknown to the application). The system sets permissions for all the files in an application so that only the user ID assign application can access them. Each process has its own virtual machine (VM), so an application's code runs in isolation from other applications. By default, every application runs in its own Linux process. Android starts the process when any of the application's components need to be executed, then shut down the process when it's no longer needed or when the system must recover memory for other applications. In this way, the Android system implements the principle of least privilege. That is, each application, by default, has access only to the components that it requires to do its no more. This creates a very secure environment in which an application cannot access of the system for which it is not given permission. However, there are ways for an application to share data with other applications a an application to access system services: It's possible to arrange for two applications...
