Android Runtime Environment Dalvik VM for each application common Linux kernel JRE x.classy.class Linux kernel VM APP …
Basics: UNIX security compare it with Windows security
Application Security Android operating system is based on multi- user Linux system. Each application is treated as a different user. Each application uses unique Linux user ID. Every application runs as a Linux process.
Application security … It's possible to arrange for two applications to share the same Linux user ID, in which case they are able to access each other's files – can run as same Linux process and share the same VM (applications use same certificate). An application can request permission to access device data such as the user's contacts, SMS messages, the mountable storage (SD card), camera, Bluetooth, and more. All application permissions must be granted by the user at install time.
Processes & Threads Every application runs in its own process and all components of the application run in that process, by default -- UI thread Any slow, blocking operations in an activity should be done in a new thread, to avoid slowing down the user interface. – If application does not respond in 5 seconds, "application not responding" (ANR) dialog appears.application not responding
Process lifecycle: Importance Hierarchy Foreground process Visible process Service process Background process Empty process “Lower importance” tasks may be killed by Android – why? How to select a lucky one from a pool?
XML Layouts Declare UI elements in XML. Android provides a straightforward XML vocabulary that corresponds to the View classes and subclasses. Instantiate layout elements at runtime. Your application can create View and ViewGroup objects (and manipulate their properties) programmatically.
Native Development Kit (NDK) Use C/C++ for development primarily for performance critical components
Summary Clean, sophsticated, yet reasonably simple. Android requires strong Java skills – heavy use of derived classes (inheritance). Development: Java code & XML definitions Reference: http://developer.android.com/sdk/installing.html http://developer.android.com/sdk/installing.html Install Android development environment and play with a few examples or try your own ideas! Marketable skill in the industry!
More references http://www.vogella.de/articles/AndroidIntent/article.html http://developer.android.com/resources/browser.html?tag=sa mple http://developer.android.com/resources/browser.html?tag=sa mple