Learn Android from APK

1. Unpack the APK file by using apktool (http://code.google.com/p/android-apktool/).

Apktool will generate the readable XML files, include the AndroidMenifest.XML and layout XML files. It also will generate the Java bytecode from java class.

2. Rename the APK to ZIP and unzip it, get the DEX file. Using dex2jar (http://code.google.com/p/dex2jar/)
Generate the JAR file.

3. Get Java file by JD (http://java.decompiler.free.fr/).
Generate the java files

4. Using Source Insight to browser the code.