Download 02 - Android Mobile Platform

Enterprise Application
Development using J2EE
Shmulik London
Lecture #2
A Crash Course to
Android Mobile Platform
Enterprise Application Development Using J2EE / © Shmulik London 2004
Interdisciplinary Center Herzeliza Israel
Context
We’ve already mentioned the jungle of
mobile platforms. For the course exercise
J2ME serves us well as it is small and easy to
learn with no much background. So a single
lecture is enough for the mobile part of the
exercises.
However we would like to encourage you to
look also at more modern platforms such as
Android and iPhone and maybe use them in
the course project.
This lecture is just a crash course for the
Android platform (mainly an hands-on demo)
to motivate you to read further.
Enterprise Application Development Using J2EE / © Shmulik London 2008
Android Architecture
Enterprise Application Development Using J2EE / © Shmulik London 2008
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Comparison with J2ME*
Top Layer
Complete Stack
APIs/SPIs
Kernel, libs, VM, framework, apps..
Big impact on security & permissions!
Very broad scope
Well defined scope
From a door-knob to PDA
A modern mobile phone
Many optional APIs not all
supported by all devices
Little control and interaction
with the phone
Higher requirement from devices
Larger common denominator
Wide differences and peculiarities
between devices
Didn’t held up to the judge of time
* We are not really comparing apples with apples, different scope, Android came up 7 years after J2ME
Enterprise Application Development Using J2EE / © Shmulik London 2008
Comparison with J2ME
Provisioning mostly
via service providers
Open Market
Standalone apps
Promotes Mash-ups
Multi-processed
Background possible on
some devices but no
interaction
Naïve UI framework
and canvas
Much richer UI set
Open GLE, effects, …
Testing with Simulator
Testing with Emulator
Very simple
More complex
Ubiquitous
Time will tell…
Enterprise Application Development Using J2EE / © Shmulik London 2008
Main Concepts
Activity
&
Views
Broadcast
Intent
Intents
Service
Data Provider
Network
Enterprise Application Development Using J2EE / © Shmulik London 2008
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Demo #1
Enterprise Application Development Using J2EE / © Shmulik London 2008
Project Structure
Enterprise Application Development Using J2EE / © Shmulik London 2008
Manifest
<manifest
xmlns:android="http://schemas.android.com/apk/res/android"
package="examples.sidekick">
<application
android:label=“SideKick"
android:icon="@drawable/sidekick">
<activity android:name="MainActivity“
android:label="SideKick">
<intent-filter>
<action
android:name="android.intent.action.MAIN"/>
<category
android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
</manifest>
Enterprise Application Development Using J2EE / © Shmulik London 2008
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Layout (main_screen.xml)
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center">
<Button android:id="@+id/criticalButton"
android:text="Should I?"
android:layout_width="100px"
android:layout_height="wrap_content"
/>
</LinearLayout>
Enterprise Application Development Using J2EE / © Shmulik London 2008
Activity
public class MainActivity extends Activity {
public void onCreate(Bundle bundle) {
super.onCreate(bundle);
setContentView(R.layout.main_screen);
Button button = (Button)findViewById(R.id.criticalButton);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
toss();
}
});
}
private void toss() {
boolean doIt = Math.random() > 0.5;
int message = doIt ? R.string.possitive : R.string.negative;
new AlertDialog.Builder(this).setTitle(message).create().show();
}
}
Enterprise Application Development Using J2EE / © Shmulik London 2008
Resources (strings.xml)
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="possitive">Yes, you should do it!</string>
<string name="negative">No, I wouldn't do it!</string>
</resources>
Enterprise Application Development Using J2EE / © Shmulik London 2008
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Demo
Enterprise Application Development Using J2EE / © Shmulik London 2004
Interdisciplinary Center Herzeliza Israel
Few things we’ll need
for the course…
• A simple game skeleton
• Networking
Enterprise Application Development Using J2EE / © Shmulik London 2008
Simple game skeleton
Enterprise Application Development Using J2EE / © Shmulik London 2008
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Simple Game Canvas
public class GameView extends View {
... // instance variables
public GameView(Context context) {
super(context);
playerBitmap = BitmapFactory.decodeResource(
getResources(), R.drawable.android_32x40);
paint = new Paint(); // for drawing the background
}
protected void onDraw(Canvas canvas) {
canvas.drawOval(new RectF( // drawing background
getWidth()/2-40, getHeight()/2-40,
getWidth()/2+40, getHeight()/2+40), paint);
canvas.drawBitmap(playerBitmap, x, y, paint);
}
}
Enterprise Application Development Using J2EE / © Shmulik London 2008
Simple Game Canvas
public class GameActivity extends Activity {
private GameView gameView;
public void onCreate(Bundle bundle) {
super.onCreate(bundle);
gameView = new GameView(this);
setContentView(gameView);
gameView.setOnTouchListener(new View.OnTouchListener() {
public boolean onTouch(View view, MotionEvent e) {
gameView.setFigureLocation(e.getX(), e.getY());
gameView.postInvalidate();
return true;
}
});
}
Enterprise Application Development Using J2EE / © Shmulik London 2008
Simple Game Canvas
protected void onStart() {
super.onStart();
gameView.setFigureLocation(
gameView.getWidth()/2, gameView.getHeight()/2);
}
}
Enterprise Application Development Using J2EE / © Shmulik London 2008
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Http Example
Enterprise Application Development Using J2EE / © Shmulik London 2008
Http Example
public class DictionaryActivity extends Activity {
private HttpClient client;
public void onCreate(Bundle bundle) {
super.onCreate(bundle);
client = new DefaultHttpClient();
setContentView(R.layout.dictionary_screen);
Button subButton = (Button)findViewById(R.id.submitButton);
subButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
EditText inputField = (EditText)
findViewById(R.id.wordField);
String word = inputField.getText().toString();
Runnable task = new FetchDefinitionTask(word);
new Thread(task, "FetchDefinition").start();
}
});
}
Enterprise Application Development Using J2EE / © Shmulik London 2008
Http Example
class FetchDefinitionTask implements Runnable {
private String word;
FetchDefinitionTask(String word) {
this.word = word;
}
public void run() {
String url = "http://127.0.0.1:8080/dictionary/dictionary"+
"?word=“+URLEncoder.encode(word);
HttpGet request = new HttpGet(url);
request.addHeader("Content-Type", "text/plain");
try {
HttpResponse response = client.execute(request);
if (response.getStatusLine().getStatusCode() != 200) {
displayResult(“Sorry, failed to fetch definition.”);
return;
}
Enterprise Application Development Using J2EE / © Shmulik London 2008
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Http Example
HttpEntity entity = response.getEntity();
String body = EntityUtils.toString(entity);
displayResult(body);
} catch (IOException e) {
Log.e("dictionary", "failed: "+url, e);
displayResult("Sorry, Failed to fetch definition!");
}
}
}
private void displayResult(final String message) {
DictionaryActivity.this.runOnUiThread(new Runnable() {
public void run() {
TextView resultField =
(TextView)findViewById(R.id.definitionField);
resultField.setText(message);
}
});
}
Enterprise Application Development Using J2EE / © Shmulik London 2008
Http Example
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center">
<LinearLayout
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<EditText android:id="@+id/wordField"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
/>
<Button android:id="@+id/submitButton"
android:text="Submit"
android:layout_width="100px"
android:layout_height="wrap_content"
/>
</LinearLayout>
<TextView android:id="@+id/definitionField"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1"/>
</LinearLayout>
Enterprise Application Development Using J2EE / © Shmulik London 2008
Http Example
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="dictionary">
<uses-permission android:name="android.permission.INTERNET"/>
<application
android:label="Online-Dictionary">
<activity android:name="DictionaryActivity" android:label="Online-Dictionary">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
</manifest>
Enterprise Application Development Using J2EE / © Shmulik London 2008
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Summary
• We only gave you a taste of
Android, there is much more
– services, data-providers, OpenGL,
Location API, XMPP, Accelerometer…
• And don’t forget the other platform
you can choose from:
– iPhone, Blackberry, Windows-Mobile…
Enterprise Application Development Using J2EE / © Shmulik London 2008
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