• Activities dictate the UI and handle the user interaction with a smartphone screen. Activity performs actions on the screen.
• Broadcast Receivers respond to broadcast messages from other application in or from the system. This is implemented as a subclass of BroadcastReceiver class and each message is recognized as an Intent object.
• Services. These are used to perform background functions.
• Intent. This is what enables inter connectivity between activities and data passing mechanism.
• Resource Externalisation which refers to strings and graphics.
• Notification for dialogue box, icon, light, notification, sound and toast
• Content Providers for sharing data between applications

• Fragments serve as a portion of user interface in an Activity.
• Views are UI elements that are drawn on-screen including buttons, lists forms, etc.
• Layouts view hierarchies that control screen format and the appearance of the views.
• Intents are messages that wire components together.
• Resources are external elements (strings, constants and drawable pictures).
• Manifest is the configuration file for the app.

• Shared Preferences store private primitive data in key-value pairs. SharedPreferences class helps to provide a general framework that allows users to save and retrieve persistent key-value pairs of primitive data types. SharedPreferences can be used to save primitive data such as booleans, floats, ints, longs and strings. This data persists across user sessions even when one’s application is killed. For more information on how to get a SharedPreferences object for one’s application click here.
• Internal Storage stores private data on the device memory. Once can save files directly on the device’s internal storage. The files saved to the internal storage are private to you application by default and other applications cannot access them either. When the user uninstalls your application, the files will then be removed.
• External Storage stores public date on the shared external storage. Every Android-compatible device can support a shared “external storage” where one’s files can be saved. This can be removable storage media (SD card) or internal (non-removable) storage.
• SQLite Databases stores structured data in a private database. Android provides full support for SQLite databases. Any databases that one creates can be accessible by name to any class in the application. Please note they are not accessible outside of the application.
• Network Connection stores data on the web with one’s own network server. In order to do network operations, one must use classes in the following packages below:

• Activity – The class representing a single screen, i.e. a Frame in AWT
• View – The UI element for example a label, button or text field. Basically anything that is seen is a view
• Intent – that which is used for invoking components. For example start the service, display a web page or broadcast a message.
• Service – the background process. These come in two types local which is accessed from the application and remote which can be accessed from other devices.
• Content Provider – these are used to share data between different applications.
• Fragment – separate parts of the activity which can be displayed in multiples at the same time.
• AndroidManifest.xml – This holds information regarding activities, permissions and content providers etc.
• Android Virtual Device (AVD) – Which is used for testing the application without need a tablet or other device.

• Starting an Activity It is normal to start a new instance of an activity by passing an intent to startActivity() method.
• Delivering a Broadcast This can be done by passing an intent to sendBroadcast(), sendStickyBroadcast(), and sendOrderedBroadcast()
• Starting a Service this can be used to perform a one-time operation, for example download a file. It’s achieved by passing an intent to startService()

Intent intent = new Intent(this, MyTestActivity.class);
       startActivity(intent);

class PrimeThread extends Thread {
        long minPrime;
        PrimeThread(long minPrime) {
            this.minPrime = minPrime;
        }
        public void run() {
            // compute primes larger than minPrime
             . . .
        }
    }

PrimeThread p = new PrimeThread(143);
    p.start();

class PrimeRun implements Runnable {
        long minPrime;
        PrimeRun(long minPrime) {
            this.minPrime = minPrime;
        }
        public void run() {
            // compute primes larger than minPrime
             . . .
        }
    }

PrimeRun p = new PrimeRun(143);
    new Thread(p).start();