Google Android - The Android Log
The Register: When is Java not Java?
November 21st, 2007 by Head Robot
Google’s cunning plan to bypass the Java license might not be cunning enough, depending on how Sun decides to play it and if they see Android as a significant threat to their Java revenues.
The Android platform can run applications developed for Java Micro Edition (J2ME) but to avoid the restrictions of Java licence Google’s platform takes the Java Byte Code (the faux-machine language into which Java applications are compiled) and converts it to their own virtual machine language: Dalvik.
By this ruse they avoid Android-based devices having to have a Java Virtual Machine, and thus avoid paying Sun for a licence or being forced to open up modifications under the J2ME open source licence.
Read the rest of the article, When is Java not Java?
Technorati Tags: Java, Sun, Google, Android, Dalvik, Virtual Machine, J2ME
Linux Devices - So, what Is Android?
November 16th, 2007 by Head Robot
John Lombardo gives a thorough overview of Google’s Android SDK at Linux Devices,
Android is a complete software stack for mobile devices such as cell phones, PDAs and high end MP3 players. The software stack is split into four layers:
- The application layer
- The application framework
- The libraries and runtime
- The kernel
Cell phone users obviously work with applications in the application layer. Android developers write those applications using the application framework. Unlike many embedded operating environments, Android applications are all equal — that is, the applications that come with the phone are no different than those that any developer writes. In fact, using the IntentFilter API, any application can handle any event that the user or system can generate. This sounds a bit scary at first, but Android has a well thought-out security model based on Unix file system permissions that assure applications have only those abilities that cell phone owner gave them at install time. The framework is supported by numerous open source libraries such as openssl, sqlite and libc. It is also supported by the Android core libraries — more on that in a second. At the bottom of the stack sits the Linux 2.6 kernel, providing the low level hardware interfaces that we all expect from a kernel. This is a Unix based system — that is, the Unix C APIs are available — but don’t expect to drop to a shell and start executing shell scripts with your old friends grep and awk. Most of the Unix utilities are simply not there. Instead Android supplies a well thought out API for writing applications — in Java using the Android core libraries.
That’s right, Android applications are almost exclusively written in Java. The Android core library is a big .jar file that is supported by the Dalvik Virtual Machine — a fast and efficient JVM work-alike that enables java-coded applications to work on the Android cell phone. This is similar to, but not the same as using Sun’s JVM directly.
Read the rest of the article, A Developer’s Perspective on Google’s Android SDK
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Technorati Tags: Developer, Android SDK, Linux, Kernel, API, Dalvik, JVM, Java