4x4 Android Development Programming the First App

an App or Android application package file (APK) .apk is a javacode compiled by Android SDK Tools with datas and ressources files. The MIME type associated with APK file is application/vnd.android.package-archive

Below is a summary of programming the first application on Android, just after having created MyFirstApp from Google. 4x4 principle : 4 points for 4 code-components famillies.

1. The principle of functionment and organization of apps population into Android is based on the model of security-sandbox where : 
-Each app is runned by a linux user with a unique userID following principle of least privileges
-Each process runs on a Darrick VM
-Requests to user datas are granted on install 
-Any app can theoretically start another app components and instantiate their classes

2.App components types : there are only 4 types

ACTIVITY
SERVICE
PROVIDER
RECEIVER

Activities are screens : StartActivity(Intent)
Services : Startservice(intent), Bindservice (intent)
Providers of content: eg contacts with Content Resolvers
Brodcast receiver (eg low battery, download finished, call for activities) : Intent Objects : sendbroadcast (intent)

3. Manifest : android manifest.xml
defines permissions
api level
hw, sw, features needed : defines screen sizes, imput configuration (user-configuration) device features (user-features)
API librairies : eg. google maps API
declaration of Components :

 ACTIVITY 
 SERVICE 
 PROVIDER
 RECEIVER

4. Ressources
example : logo.png in Res/drawable having a RESSOURCEID in compiled code.