- Written in Java language
- They are compiled to Android’s own bytecode format, Dalvik executable(DEX)
- Doesn’t have a single entry-point, such as the main method in Java
- Four components
- Activities: visible parts of an application
- Services: run in the background and are not interacting with the user directly, used for long running background such as mp3 playback
- Broadcast receivers: react to global events, such as incoming calls or text messages
- Content providers: implement domain-specific databases for, e.g. contacts
- onCreate(): gets called when the activity is launched for the first time
- Android Emulator: virtual mobile device that runs on a computer and is similar to a real device.
- Android API calls
- Log.i(String tag, String msg):
- Static methods which writes an info messages to the log
- The log can be browed using the tool LogCat
- findViewById(int id)
- returns references to GUI objects
- Log.i(String tag, String msg):