1. Mobile Software Development Framework: Android
2/23/2011
Y. Richard Yang

2. Admin. Homework 2 due today Midterm: Wednesday after spring break
Please schedule time to meet with the TA to demo your program
Midterm: Wednesday after spring break

3. Recap: Mobile Programming Requirements
Handle heterogeneous devices/configurations
Be extremely efficiency on using resources (memory, battery, …)
Easy programming for event-driven programming …

4. Recap: tinyOS Customized OS for each app. Reusability achieved through
Components and interfaces structure
Execution model: two threads
One for tasks
One for event handling

5. HelloWorldMIDlet.java import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
public class HelloWorldMIDlet extends MIDlet
implements CommandListener {
private Command exitCommand;
private Display display;
private TextBox t;
public HelloWorldMIDlet() {
display = Display.getDisplay(this);
exitCommand = new Command("Exit", Command.EXIT, 2);
t = new TextBox(“CS434", "Hello World!", 256, 0);
t.addCommand(exitCommand);
t.setCommandListener(this); }
public void startApp() { display.setCurrent(t); }
public void pauseApp() { }
public void destroyApp(boolean unconditional) { }
public void commandAction(Command c, Displayable s) {
if (c == exitCommand) {
destroyApp(false);
notifyDestroyed();

6. Recap: J2ME
Scale down a popular programming environment to ease learning
Use virtual machines to mask device heterogeneity
Use configuration/profile to handle device heterogeneity to avoid using lowest common denominator
MIDLet and Displayable to support user-interface driven applications
MIDLet manages app life cycle
Displayable has commands and provides command listener
Introduce persistent record store

7. Recap: Android
Scale down a popular programming environment to ease learning
Use virtual machines to mask device heterogeneity
Activity and View

8. Activity A screen with which users can interact
Activity has life cycle to yield resources

9. View
A view component is a building block for user interface components.
Widget Toolbox
TextView, EditText, Button, Form, TimePicker…
ListView
Layout
Positions of controls
LinearLayout, Relativelayout

10. View by XML Java Code main.xml Layout of visual interface Initialize
Access
TextView myTextView = (TextView)findViewById(R.id.myTextView);
<?xml version=”1.0” encoding=”utf-8”?>
<LinearLayout xmlns:android=”
android:orientation=”vertical”
android:layout_width=”fill_parent”
android:layout_height=”fill_parent”>
<TextView
android:layout_height=”wrap_content”
android:text=”Hello World, HelloWorld”
/>
</LinearLayout>
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.main); }

11. User Interaction Event
onKeyDown. onKeyUp
onTrackBallEvent
onTouchEvent
registerButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View arg0) {….}}
myEditText.setOnKeyListener(new OnKeyListener() {
public boolean onKey(View v, int keyCode, KeyEvent event) {
if (event.getAction() == KeyEvent.ACTION_DOWN)
if (keyCode == KeyEvent.KEYCODE_DPAD_CENTER) { …
return true; }
return false;
}});

12. Example: TipCal

13. Application Framework (Android): Key Concepts
Activity and view
Visible screen for user interaction
External resources

14. External Resources

15. Application Framework (Android): Key Concepts
Activity and view
Visible screen for user interaction
External resources
Service

16. Service: Working in Background
A basic function of Android Service:
A facility for an application to tell the system about something it wants to be doing in the background (even when the user is not directly interacting with the application).
The system to schedule work for the service, to be run until the service or someone else explicitly stop it.
NO GUI, higher priority than inactive Activities
Note
A Service is not a separate process. The Service object itself does not imply it is running in its own process; unless otherwise specified, it runs in the same process as the application it is part of.
A Service is not a thread. It is not a means itself to do work off of the main thread (to avoid Application Not Responding errors).

17. Application Framework (Android): Key Concepts
Activity and view
Visible screen for user interaction
External resources
Service
Intercommunications
App
Communication among apps:
Intent
broadcast
data provider

18. Application and Component Glues
Intent
An intent is an abstract description of an operation to be performed.
To invoke operations from your own or others
Can pass data back and forth between app.
Intent Filter
Register Activities, Services, and Broadcast Receivers as being capable of performing an action on a particular kind of data.

19. Intent Description <Component name> Action Data
Category, e.g., LAUNCHER

20. Intent Usage
Pass to Context.startActivity() or Activity.startActivityForResult() to launch an activity or get an existing activity to do something new.
Pass to Context.startService() to initiate a service or deliver new instructions to an ongoing service.
Pass to Context.bindService() to establish a connection between the calling component and a target service. It can optionally initiate the service if it's not already running.
Pass to any of the broadcast methods (such as Context.sendBroadcast(), Context.sendOrderedBroadcast(), or Context.sendStickyBroadcast()) are delivered to all interested broadcast receivers. Many kinds of broadcasts originate in system code.

21. Android: Broadcast Receiver
Sending a broadcast:
Context.sendBroadcast(Intent intent, String receiverPermission)
Context.sendOrderedBroadcast()
Receiving broadcast:
Intent registerReceiver (BroadcastReceiver receiver, IntentFilter filter)

22. Intent Resolution: Explicit
Explicit intents: component identified
Intent myIntent = new Intent(IntentController.this, TipCal.class);
startActivity(myIntent);
Make sure AndroidManifest.xml announces activities to be started
<application
<activity android:name=".IntentController"
android:label="Intent1">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".TipCal"></activity>
</application>

23. Intent Resolution: Implicit
Implicit intents
System matches an intent object to the intent filters of others

24. Intent filter
action
category
data

25. Intent Example II: Implicit
String action = "android.intent.action.VIEW";
Uri data = Uri.parse("
Intent myIntent = new Intent(action, data);
startActivity(myIntent);
AndroidManifest.xml file for com.android.browser
<intent-filter>     <action android:name="android.intent.action.VIEW" />     <category android:name="android.intent.category.DEFAULT" />     <scheme android:name="http" />     <scheme android:name="https" />     <scheme android:name="file" /> </intent-filter>

26. Intent Example II: Implicit
String action = "android.intent.action.DIAL";
String phno = "tel: ";
Uri data = Uri.parse(phno);
Intent dialIntent = new Intent(action, data);
startActivity(dialIntent);

27. A Design Template: Invoker
String action = “com.hotelapp.ACTION_BOOK";
String hotel = “hotel://name/“ + selectedHotel;
Uri data = Uri.parse(hotel);
Intent bookingIntent = new Intent(action, data);
startActivityForResults(bookingIntent, requestCode);

28. A Design Template: Provider
<activity android:name=".Booking" android:label=“Booking">
<intent-filter>
<action android:name=“com.hotelapp.ACTION_BOOK" />
<data android:scheme=“hotel" android:host=“name”/>
</intent-filter>
</activity>
For more complex data passing, please read the tutorial

29. A Design Template: Provider
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Intent intent = getIntent(); // why am I called
String action = intent.getAction();
Uri data = intent.getdata();
String hotelName = data.getPath();
// do the booking
setResult(RESULT_OK);
finish(); }