Hello World on the Android Platform

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Hello World on the Android Platform

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Getting the Tools Setup

Need to Install… Eclipse (the IDE) Android SDK Java JDK (not just the JRE)

Quick Start Guide is Here:

http://developer.android.com/sdk/index.html

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http://developer.android.com/sdk/index.html


Integration

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Then you need to integrate Eclipse and The Android Developer Toolkit

http://developer.android.com/sdk/eclipse-adt.html




Android SDK Versions

You then need to download SDK versions of Android to run your program against

The Android SDK Manager in Eclipse will do this

You don’t need the latest version – it’s slow API 7 (Android 2.1) is good & compatible with

most devices


The AVD

An Android Virtual Device (a simulator) needs to be created.

You will specify this in Eclipse Includes the features that this virtual phone will

have, such as touch screen, etc.


The Tutorial

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http://developer.android.com/resources/tutorials/hello-world.html






The Result

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Android Virtual Device can be a little quirky and take time to load


Android Application Fundamentals


Getting the Tools Setup

Assuming you have Eclipse And the SDK setup

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Android Online Tutorial

http://developer.android.com/guide/topics/fundamentals.html

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App Fundamentals Apps are stored in an .apk file

Components in a Program Activities – most important part Services Broadcast Receivers Content Providers Intents – a message that is sent Widgets Notifications

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Activities A GUI element An activity can contain views such as buttons

or check boxes

One Activity is designated (in the Manifest) as where to “start” the application

These are the “forms” of the application – the presentation layer


Services

Not part of the GUI A background process

Playing audio Network communication Can be spawned in another thread


Broadcast Receivers

A “listener” that receives announcements From the system – battery is low Broadcast Receivers could notify the user of

something, for example

A broadcast receiver receives an “Intent” – a message, and respond to create an event-driven application


Content Providers

A method of interprocess communication to make data from your app available to other apps

Or, vice-versa Implemented through a ContentProvider and

a ContentResolver (to get the data). Example: The Contacts list in the phone –

your application could access this.


Intents

The actual message that is sent

An Intent to a Broadcast Receiver might announce that a picture has been taken

You can send an Intent to another application as well.

Intents are commonly used to launch a second Activity (screen)


Widgets

Visual components that can be added to the user’s home screen

Special broadcast receivers


Notifications

Signal a user without interrupting the current activity.

Example – text message comes in.

We can trigger those notifications programmatically


The Result

Think about apps as a collection of these independent pieces, passing messages to one another.


Application and ActivityClasses


The Application Class

Your app will extend the Application class

Your application object is a singleton (only one object may be instantiated)

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Application Classpublic class MyApplication extends Application{

private static MyApplication singleton;

@Override public final void onCreate() {

super.onCreate(); // call the parentsingleton = this;// any other of my code

} @Override public final void onTerminate() {

super.onTerminate(); // call the parent// now my code

}


MyApplication class

I can override… onCreate( ) onTerminate( ) – no guarantee this gets called onLowMemory( ) onConfigurationChanged( )

Need to call the superclass methods in each of your overridden methods

Sometimes the system kills your app w/ no notice


Android Activity

The basis for the application

The program will start running here, and we can add user interface elements (such as Views) to the Activity

This is done in xml files in the ‘res’ folder


Android Activities

import android.app.Activity;import android.os.Bundle;

public class MyActivity extends Activity{ // override the base class onCreate() }


Activities -> Views

We need to add a view to our activity to create a GUI


Resources

The /res folder contains xml files We can specify in xml

GUI elements (using xml is preferred to using code)

String constants to be used in the program Other resources the program needs, such as

sounds or images


DroidDraw

DroidDraw can help with the screen layouts

http://www.droiddraw.org/




Styles and Themes

You can also create a style for all of the Activities in your app

Similar to css for web pages

http://developer.android.com/guide/topics/ui/themes.html




Hello World on the Android Platform

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