Android101

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Android Apps 101David Marques | March 11th, 2010

About Me

Lots of mobile fun :)

● Developer tools for Java ME● Mobile Device Emulator

● Eclipse Foundation Committer

Lots of mobile fun :)

What is Android?

“Android is a software stack for mobile devices that includes an operating system, middleware and key applications”

Android App Anatomy

An android application is an island of components

Application

Linux Process

Activity

Content Provider

Service

Intent Receiver● Application Package

● Android Manifest

● Defaults to 1 process per application

● Defaults to 1 thread per application

How do we tell the system what we have to offer?

Meet the Manifest

<manifest> <application> <uses-permission> <activity>

<receiver> <service> <provider>

Meet the Main Thread

● Managed Life Cycle

● System events, life cycle management callbacks and UI updates happen on the Main Thread

● Get away from it :)

Linux Process

Main Thread

Looper

Content Provider

Service

Intent Receiver

ActivityMessage

QueueAndr

oid

Syst

em

What does he mean with GET AWAY FROM

THE MAIN THREAD??????

Android Security Model

● Proven security model

● Process isolation by UID

● Permission based model

Basic Building Blocks

Activities Services

IntentReceivers

Content Providers

Activities

IS a way to represent a particular

operation

IS NOT necessarily a screen element

What is a Task ?

If Activities are managed components

there must be a life cycle?

How does an Activity look like?

Activity.java + layout.xml

Activity.java

public class Hello extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); }}

● AndroidManifest.xml

<activity android:name=".Hello" android:label="@string/app_name"><intent-filter>

<action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" />

</intent-filter> </activity>

layout.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"><TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello" /></LinearLayout>

Activities Services

IntentReceivers

Content Providers

Content Providers

● Content providers store and retrieve data and make it accessible to all applications;

● They're the only way to share data across applications;

● There's no common storage area that all Android packages can access.

● How a content provider actually stores its data under the covers is up to its designer!

audio - video - images - personal contact information

Basic Concepts

Hows does it looks like ?

public class ExampleProvider extends ContentProvider {

public Cursor query (Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {// Returns data to the caller via a Cursor object

}public Uri insert (Uri uri, ContentValues values) {

// Inserts new data into the content provider}public int update (Uri uri, ContentValues values, String selection,

String[] selectionArgs) {// Updates existing data in the content provider

}public int delete (Uri uri, String selection, String[] selectionArgs) {

// Deletes data from the content provider}

}

<provider android:name="com.example.autos.AutoInfoProvider" android:authorities="com.example.autos.autoinfoprovider"

. . . /></provider>

Activities Services

IntentReceivers

Content Providers

Services

A Service is an application component that can perform long-running operations in the

background;

It does not provide an user interface element;

Started Services

When the operation is done, the service should stop itself.

Started Services

When the operation is done, the service must stop itself.


public class ExampleService extends Service {

public void onCreate() { // The service is being created } public int onStartCommand(Intent intent, int flags, int startId) { // The service is starting, due to a call to startService() return mStartMode; } public void onDestroy() { // The service is no longer used and is being destroyed }}

<service android:name=".ExampleService" />

http://developer.android.com/guide/topics/manifest/service-element.html

Well well well, long-running operations

+ background

And he said GET AWAY FROM THE MAIN THREAD

??????

“Caution: A service runs in the main thread of its hosting process the service does not create its own thread and does not run in a separate process (unless you specify otherwise).”

“If your service is going to do any CPU intensive work or blocking operations (such as MP3 playback or networking), you should create a new thread within the service to do that work.”

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

“Caution: A service runs in the main thread of its hosting process the service does not create its own thread and does not run in a separate process (unless you specify otherwise).”

“If your service is going to do any CPU intensive work or blocking operations (such as MP3 playback or networking), you must create a new thread within the service to do that work.”

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

I _ _ E _ _ _ E _ _ I _ E

I N T E N T S E R V I C E_ _ _ _ _ _ _ _ _ _ _ _ _

● Creates a default worker thread;

● Creates a work queue, so you never have to worry about multi-threading;

● Stops the service for you;

http://developer.android.com/reference/android/app/IntentService.html

Bound Service

●Allows application components to bind to it

●Expose application's functionality

public class ExampleService extends Service { IBinder mBinder; // interface for clients that bind

public IBinder onBind(Intent intent) { // A client is binding to the service with bindService() return mBinder; } public boolean onUnbind(Intent intent) { // All clients have unbound with unbindService() return mAllowRebind; } public void onRebind(Intent intent) { // A client is binding to the service with bindService(), // after onUnbind() has already been called }}


http://developer.android.com/guide/topics/fundamentals/bound-services.html

Android Interface Definition Language (AIDL)

Activities Services

IntentReceivers

Content Providers

Intent Receivers

Its all about Intents!

“Intents is the mechanism by which the applications talk to each other and with the system”

ACTION_BOOT_COMPLETED - ACTION_BATTERY_CHANGED - ACTION_POWER_CONNECTED – ACTION_SHUTDOWN –

ACTION_MEDIA_MOUNTED – ACTION_NEW_OUTGOING_CALL

● Super Fast Life-Cycle: ONLY ONE CHANCE :)

● Permissions can be enforced either by the sender or receiver


public class ExampleReceiver extends BroadcastReceiver {

public void onReceive(Context context, Intent intent) {// Thats your ONLY CHANCE to do anything!// Once it returns GAME OVER

}}

● AndroidManifest.xml

<uses-permission android:name="android.permission.RECEIVE_SMS"></uses-permission> ...<receiver android:name=".SMSReceiver" android:enabled="true">

<intent-filter><action android:name="android.provider.Telephony.SMS_RECEIVED" />

</intent-filter></receiver>

http://developer.android.com/reference/android/content/BroadcastReceiver.html

● DO run on a background thread if its not UI related;

● DO consider multiple form factors;

● DO respect the user preferences;

● DO consider that you are not running alone on the system;

● DO hire a designer;

● DO collaborate with other applications;

● DO support landscape and portrait;

● DO consider publishing on the Android Market

DON'Ts

● DONT replace the back, home, search and menu features;

● DONT remove the status bar unless you need to;

● DONT allocate objects unless you need to;

● DONT hold Context object references;

● DONT update Widgets toooooooo often;

● DONT wake up the system to do nothing;

● DONT log sensitive user information;

● DONT use non public APIs =X

Development environment

Eclipse + ADT = http://developer.android.com/sdk/eclipse-adt.htmlhttp://eclipse.org

edit+debug+log+compile+package+navigate file system+analyze memory+

edit user interface+emulate device+ localize+analyze performance+...

Questions ?

Lets Code :)

Android Apps 101David Marques | March 11th, 2010

Android101

Technology

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