Learn Android

Android Developer Days is reloading for 2013

2013-03-26T10:50:00.000+02:00

Android Developer Days(ADD) is now reloading for 2013. ADD 2013 will take place on June 14/15, 2013 in METU Cultural and Convention Center, Ankara, Turkey.
ADD 2013 is targeted to be the one of the biggest international tech related community organization in EMEA. The first ADD was on May 21/22, 2012. There were 700 participants and more than 30 speakers. ADD 2013, June 14/15, 2013, will have more participants, more fun, more networking and more inspiration.
Take a look at the About, Call for submissions and Participation Form.

ADD is a community conference organized by:

Call For Submissions

You can join the conference with the followings:

Presentations that is 15-20 minutes or 40-45 minutes long.

Quickie: 10 minute presentation in small rooms.

Poster: You can show your applications in a place dedicated for posters.

Workshop: Presentations with hands on coding, 40 minutes long.

Indicate your contribution in OpenConf and please indicate how much your presentation is going to take when submitting it to OpenConf Deadline of Call for Submissions is 1st May 2013.

Subjects:

Future Technologies

Mobile World

Future of Mobile World

New Generation Mobile Devices (Project Glass)

Android OS

Future Versions

Android in Different Architectures

Android in Different Areas(Industry, Defense, Home Electronics etc.)

Android App Development

New Features and Capabilities

App Development Best Practises

Android SDK Tools

UI(User Interface) / UX (User Experience) Design

App Monetization

Ad Integration

In-app Billing

User Statistics

Android NDK

Cross Platform App Development Frameworks

HTML5

Javascript

Game Development

Google TV

Google Playstore

Communication Solutions (NFC, Bluetooth, Wi-fi)

3G, 4G Wide Band Communication

Cloud

Google Cloud Messaging for Android

Google App Engine

Augmented Reality

Social Media

Location Based Services and Maps

Mobile Education (Fatih Project)

Mobile Payment

Security

Arduino

Software Development Methodologies

Success Stories

GWT

Developers: Your perspectives do matter to the mobile industry.

2012-11-30T20:25:00.001+02:00

Hello developers, please share your opinions and experience in mobile development by participating in the following survey
https://s.zoomerang.com/s/pivotalperspectivesnovember

Marmalade SDK: Exception: Multiply Overflow

2012-10-16T10:53:00.001+02:00

I was performing some transformations (scaling) on 2D sprites like this:

CIwMat2D matrix;
rot.Scale(IW_FIXED(2));

When I ran the app I received the following exception:

IwAssert failure (GEOM, 350). Message: Multiply overflow

The avoid this exception, you must set your matrix to the Identity matrix before applying transformations on it like this:

CIwMat2D matrix;
matrix.SetIdentity();
rot.Scale(IW_FIXED(2));

Marmalade SDK: Data cache overflow allocating XXX. Increase [GX] DataCacheSize (currently XXXXX) exception

2012-10-10T15:16:00.000+02:00

You may encounter this error if your application requires caching some data but the reserved cache size by your application does not have enough space.

to solve this, just increase the reserved cache space defined in your app.icf file:

[GX]
DataCacheSize=30000

Marmalade SDK: Output Debug messages

2012-10-10T13:09:00.000+02:00

If you want to output debug messages in your output console in Visual studio, you can do it in two ways:

Use standard C++ output stream cout
```
cout<<"Your Message"<<endl;
```

use the Marmalade s3eDebug module: first include the header:

#include "s3eDebug.h"

then

s3eDebugOutputString("Your Message");

to display integers you have to convert them to C style strings first:

int x=10;
char buffer[10];
//convert the int to a char array
sprintf(buffer,"%d",x);
s3eDebugOutputString(buffer);

Marmalade SDK: Exception cannot open file iwui_style/style.group.bin for serialising

2012-10-10T11:31:00.001+02:00

I made a simple IW2D app with Marmalade SDK, it worked fine in the Windows emulator but when I deployed to Android I received this exception:

cannot open file iwui_style/style.group.bin for serialising (read), Did you include this file in your mkb assets block

The solution was to add this block to my MKB file

assets
{
    (data-ram/data-gles1)
    ui.group.bin
    (data-ram/data-gles1)
    iwui_style/style.group.bin
}

App Developers: check this survey

2012-10-06T13:55:00.000+02:00

“I came across this invitation for developers to give their perspectives to mobile industry leaders such as Microsoft, Google, Apple and RIM. Check it out”

It's a really nice survey, participate and share your experience with others

Android Developers Blog: Introducing Android 4.1 (Jelly Bean) preview platform, and more

2012-06-27T19:56:00.001+02:00

Android Developers Blog: Introducing Android 4.1 (Jelly Bean) preview platform, and more

Playstation Suite SDK: referencing DLLs and Intellisense

2012-04-24T15:10:00.000+02:00

An issue I faced today while testing the Playstation Suite SDK, I created a sample project in the PSS Studio and added a reference to a custom made DLL.

I found that the intellisense (auto completion) of the editor couldn't perceive the newly added DLL, it provided no auto-completion for the classes within the library.

I got the solution to this from here http://www.gamefromscratch.com/post/2012/04/20/Initial-issues-with-Playstation-Suite-SDK.aspx

just restart the PSS Studio and everything will work just fine

SUNPHOS featured in Android Police

2012-02-22T10:14:00.000+02:00

SUNPHOS is feautered in Android Police as one of the best 43 apps in the last 2 weeks

SUNPHOS

2012-02-12T21:20:00.000+02:00

SUNPHOS is a professional android application for photographers who needs to plan a day around the constantly changing character of sunlight. It provides you with valuable information like day length,sun rise & sun set, golden hour, twilight and more.

SUNPHOS Features:

Search Sun Track.
View Mode.
Search Sun Position.
Daily Report on sun info.

Winners of the Ice Cream Sandwich VS iOS5 contest

2011-11-09T18:41:00.000+02:00

Dear readers we are glad to announce the winners of our Ice Cream Sandwich VS iOS5 contest:

The winners of the first prize: Android a Complete Course:
Jim from http://sakiko.com/
and
Believer.

The winner of the second prize: Android a Quick Course:
Corneliu Dascalu

The winners of the third prize Android, an Enterprise Edition Vision:
Will.i.am

for the winners please contact me at m.s.ramzy@gmail.com to send you the copies of the books
thanks a lot for all the participants and good luck next time.

Ice Cream Sandwich GridLayout

2011-10-22T23:14:00.000+02:00

Android 4.0 (Ice Cream Sandwich) introduced a new type of layouts: the Gridlayout.
Gridlayout is like the <Table> tag in HTML. child widgets are arranged in Cells made of Rows and Columns.

Grid layout is a ViewGroup that can be used in constructing dashboard activities like that one in the Google Plus application:

so let's see what we can do with the GridLayout:
we'll construct a simple dashboard layout like this:

<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:rowCount="5"
    android:columnCount="3"
    >

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button 1"
        android:layout_row="0"
        android:layout_column="0"
        android:layout_marginLeft="5dp"
         />
    
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button 2"
        android:layout_row="0"
        android:layout_column="1"
        android:layout_margin="5dp" />
    
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button 3"
        android:layout_row="1"
        android:layout_column="0"
        android:layout_margin="5dp" />
    
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button 4"
        android:layout_row="1"
        android:layout_column="1"
        android:layout_margin="5dp" />
    
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button 5"
        android:layout_row="2"
        android:layout_column="0"
        android:layout_margin="5dp" />
    
    

</GridLayout>

Widgets are placed in position specified by android:layout_column and android:layout_row properties.
we can organize the widgets in a similar way by using the new Space View like this:

<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:rowCount="5"
android:columnCount="3"

>

<Space
android:layout_width="5dp"
android:layout_height="5dp"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button 1"
android:layout_row="0"
android:layout_column="0"
/>
<Space
android:layout_width="5dp"
android:layout_height="5dp"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button 2"
android:layout_row="0"
android:layout_column="1"
/>
<Space
android:layout_width="5dp"
android:layout_height="5dp"/>

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button 3"
android:layout_row="1"
android:layout_column="0"
/>
<Space
android:layout_width="5dp"
android:layout_height="5dp"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button 4"
android:layout_row="1"
android:layout_column="1"
/>
<Space
android:layout_width="5dp"
android:layout_height="5dp"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button 5"
android:layout_row="2"
android:layout_column="0"
/>
<Space
android:layout_width="5dp"
android:layout_height="5dp"/>

</GridLayout>

Contest: Do you think Android Ice Cream Sandwich will beat Apple iOS 5

2011-10-08T22:15:00.001+02:00

Hello everybody.
Google will release the next major Android update: Android 4.0 (Ice cream Sandwich) along with it's next flagship phone: the Nexus Prime.

Join our Contest and have the chance to win a copy of one of these wonderful Android books:

all you've got to do is to drop a comment answering the following question:

Do you think Android Ice Cream Sandwich will beat Apple iOS 5 ?

the contest ends on November 7th, winners will be announced then.

waiting for your comments

Symbyo Technologies: Cloud Computing and Mobile Application Development

2011-09-18T11:34:00.000+02:00

Symbyo Technologies: Cloud Computing and Mobile Application Development

Android Developers Blog: Preview of Google TV Add-on for the Android SDK

2011-08-23T12:46:00.000+02:00

Android Developers Blog: Preview of Google TV Add-on for the Android SDK

Official Google Blog: Supercharging Android: Google to Acquire Motorola Mobility

2011-08-15T13:48:00.000+02:00

Official Google Blog: Supercharging Android: Google to Acquire Motorola Mobility

Android Developing: Remove Auto focus from Edit Text

2011-08-08T11:12:00.000+02:00

Android Developing: Remove Auto focus from Edit Text: "When start Android application, it always auto focus EditText box. Here we give explain how to remove auto focus from EditText. Add your..."

Implementing Search activities

2011-08-06T12:14:00.002+02:00

Most Android phones have a search button. this button is used to search contacts,applications or anything on the phone. We can make use of the search functionality in our apps.

In this post we're going to see how to implement search functionality to search for entries stored in a databaseand display them in a ListView.

Creating database:

our database has two tables: Countries and Names:

public class DBHelper extends SQLiteOpenHelper {

 public DBHelper(Context context) {
  super(context, "DemoDB", null, 1);
 }

 @Override
 public void onCreate(SQLiteDatabase db) {
  StringBuilder builder=new StringBuilder();
  // countries table
  builder.append("CREATE TABLE Countries ");
  builder.append("(_id INTEGER PRIMARY KEY AUTOINCREMENT,");
  builder.append("NAME TEXT) ");
  db.execSQL(builder.toString());
  // Names table
  // Virtual table for full text search
  builder.setLength(0);
  builder.append("CREATE VIRTUAL TABLE NAMES USING FTS3");
  builder.append("(");
  builder.append("name TEXT) ");  
  db.execSQL(builder.toString());
  builder=new StringBuilder();

  //dummy  data
  InsertData(db);

 }

  void InsertData(SQLiteDatabase db)
  {
   ContentValues cv=new ContentValues();
   cv.put("NAME","USA");
   db.insert("Countries", "NAME", cv);
   cv.put("NAME","UK");
   db.insert("Countries", "NAME", cv);
   cv.put("NAME","Spain");
   db.insert("Countries", "NAME", cv);
   cv.put("NAME","ITALY");
   db.insert("Countries", "NAME", cv);
   cv.put("NAME","Germany");
   db.insert("Countries", "NAME", cv);

    cv=new ContentValues();
    cv.put("name","John");
    db.insert("NAMES", "name", cv);
    cv.put("name","Jack");
    db.insert("NAMES", "name", cv);
    cv.put("name","Ann");
    db.insert("NAMES", "name", cv);
    cv.put("name","Adam");
    db.insert("NAMES", "name", cv);
    cv.put("name","Sarah");
    db.insert("NAMES", "name", cv);

  }

 @Override
 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
  // TODO Auto-generated method stub

 }
}

notice that the Names table is a VIRTUAL table. we created it as virtual to make use of Full Text Search (FTS3) feature in SQLite. this feature makes queries faster than that in regular tables.

then we add two functions to retrieve all rows from both tables:

/**
  * Return all countries
  * @return
  */
 public ArrayListgetCountries(){
  ArrayList countries=new ArrayList();
  SQLiteDatabase db=this.getReadableDatabase();
  Cursor c=db.rawQuery("select * from Countries", null);
  while(c.moveToNext()){
   String country=c.getString(1);
   countries.add(country);
  }
  c.close();
  return countries;
 }
/**
  * Return all names
  * @return
  */

 public ArrayListgetNames(){
  ArrayList names=new ArrayList();
  Cursor c=this.getReadableDatabase().rawQuery("select * FROM Names", null);
  while(c.moveToNext()){
   String name=c.getString(0);
   names.add(name);
  }
  c.close();
  return names;
 }

and another two functions to retrieve data based on a search string:

/**
  * Return all countries based on a search string
  * @return
  */
 public ArrayListgetCountriesSearch(String query){
  ArrayList countries=new ArrayList();
  SQLiteDatabase db=this.getReadableDatabase();
  Cursor c=db.rawQuery("select * from Countries where NAME LIKE '%"+query+"%'", null);
  while(c.moveToNext()){
   String country=c.getString(1);
   countries.add(country);
  }
  c.close();
  return countries;
 }
/**
  * Return all names based on a search string
  * we use the MATCH keyword to make use of the full text search
  * @return
  */
 public ArrayListgetNamesSearch(String query){
  ArrayList names=new ArrayList();
  Cursor c=this.getReadableDatabase().rawQuery("select * FROM Names WHERE name MATCH '"+query+"'", null);
  while(c.moveToNext()){
   String name=c.getString(0);
   names.add(name);
  }
  c.close();
  return names;
 }

Implementing The activity:

then we will create our activity that has a list view like this:

<?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"
    >
<ListView
android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/list"/>
</LinearLayout>

we load data from database like this:

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        list=(ListView)findViewById(R.id.list);

            DBHelper helper=new DBHelper(this);
            ArrayList items=helper.getNames();
            ArrayAdapter adapter=new ArrayAdapter(this, android.R.layout.simple_list_item_1,items);
            list.setAdapter(adapter);
}

Handling the search dialog:

In order to handle the search dialog ourselves we need to create a xml file with search configurations such as the search dialog title, voice search capabilities, content provider for auto complete and so on. we create a file with the name searchable.xml in res/xmldirectory:

<?xml version="1.0" encoding="utf-8"?>
<searchable xmlns:android="http://schemas.android.com/apk/res/android"
    android:label="@string/app_name"
    android:hint="@string/hint"  >
</searchable>

the android:hint attribute denotes a string that acts as a water mark on the search text box.
then we need to add an Intent Filter in out app's AndroidManifest.xml file to our activity to handle the search dialog:

<activity android:name=".MainActivty"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
             <intent-filter>
            <action android:name="android.intent.action.SEARCH" />
        </intent-filter>
        <meta-data android:name="android.app.searchable"
                   android:resource="@xml/searchable"/>
        </activity>

Understanding the Search process:

when you press the search button, type some text and click on search the activit's onSearchRequested() function is called, then an Intent with the action Intent.ACTION_SEARCH is created and you activity is re-created with this intent.

the search intent has you search string as a string extra with the name SearchManager.QUERY. also it can carry a bundle of other extras with the name SearchManager.APP_DATA.

what if the device doesn't have a Search button:

not all Android devices have a search button, so we can start the search dialog manually by calling the activity's onSearchRequested() from a button or a menu item:

@Override
     public boolean onCreateOptionsMenu(Menu menu) {
     menu.add("Search").setOnMenuItemClickListener(new OnMenuItemClickListener() {

   @Override
   public boolean onMenuItemClick(MenuItem item) {
                                //launch the search dialog
    onSearchRequested();
    return true;
   }
  });
     return true;
    }

Adding extras to the search dialog:

we can pass some extra data as a bundle with our search dialog or an initial search string by overriding the activity's onSearchRequested():

@Override
    public boolean onSearchRequested() {
     Bundle bundle=new Bundle();
  bundle.putString("extra", "exttra info");
  // search initial query
  startSearch("Country", false, bundle, false);
  return true;
    }

Handling the search query:

we said before that the search query is passed as a String extra when our activity is re-created. so we can handle the searcgh string in our onCreate() like this:

@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        list=(ListView)findViewById(R.id.list);

        DBHelper helper=new DBHelper(this);
        Intent intent=getIntent();
        // if the activity is created from search
         if(intent.getAction().equals(Intent.ACTION_SEARCH)){
          // get search query
          String query=intent.getStringExtra(SearchManager.QUERY);
          ArrayList items=helper.getNamesSearch(query);
          //get extras, just for demonstration
          Bundle bundle=intent.getBundleExtra(SearchManager.APP_DATA);
             String info=bundle.getString("extra");
          Log.v("extra", info);
          //bind the list
                ArrayAdapter adapter=new ArrayAdapter(this, android.R.layout.simple_list_item_1,items);
                list.setAdapter(adapter);
         }
        //activity created normally
        else{
         ArrayList items=helper.getNames();
            ArrayAdapter adapter=new ArrayAdapter(this, android.R.layout.simple_list_item_1,items);
            list.setAdapter(adapter);
        }
        helper.close();
    }

we just extract the search string and any other extras and perform our search logic based on the search string.
and that's was all about implementing search

2011-08-05T12:14:00.000+02:00

In this post we will see how can a client application call the methods of a service defined in another application. this is achieved through Android Interface Definition Language (AIDL).

AIDL is a java like language that enables you to define an interface that both the application defining the service and the client application implement it.

the interface defines the functions that are needed to be called in the client application.

Defining the AIDL file:

AIDL syntax is similar to that of Java, we can use the following data types in AIDL:

primitive data types: int, long, char, boolean,....
String.
CharSequence.
List (ArrayList,Vector,...).

the AIDL file is defined as follows:
open a notepad file and paste the following code in it:
```
package com.mina.servicedemo;

// service interface
interface IRemoteService {
    //sample method
    String sayHello(String message);
}
```
take care of the package name com.mina.servicedemo.
we defined a methods sayHello(String message) that returns a string.
save the file with the name IRemoteService and change it's extension to .aidl.
copy the file to the src folder of your project.
once you save and build the file, Android generates an interface java file with the name IRemoteService.java in the gen folder if the project.

Defining the Service:

now we want our service to expose this interface to client applications, so we return an implementation of the service in the onBind() method of our service:

package com.mina.servicedemo;

import com.mina.servicedemo.IRemoteService.Stub;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.os.RemoteException;
import android.widget.Toast;

public class DemoService extends Service {

 @Override
 public IBinder onBind(Intent arg0) {
  return mBinder;
 }

 // implementation of the aidl interface
 private final IRemoteService.Stub mBinder=new Stub() {

  @Override
  public String sayHello(String message) throws RemoteException {
   return "Hello "+message;

  }
 };

 }
}

the last thing to do in the service is to make its exported attribute in the AndroidManifest.xml file set to true like this:

<service android:name="DemoService" android:exported="true"></service>

our app structure can be like this:

Consuming the service at the client application:

now to our client application where we want to invoke methods from our service. the client application is a separate application with a different package name than that where the service is defined.

the client application needs a reference to the AIDL interface defined in the original applcation, this is done through the following steps:

in the client applicatio create a package with the same package name of that the service is defined in: com.mina.servicedemo.
copy the AIDL file in this package.
save and build and a new file called IRemoteService.java is generated. your app structure should be like this:

and we invoke the servcice methods in our activity like this:

package com.mina.serviceclient;

import com.mina.servicedemo.IRemoteService;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Log;

public class MainActivity extends Activity {

 IRemoteService mRemoteService;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Intent serviceIntent=new Intent();
        serviceIntent.setClassName("com.mina.servicedemo", "com.mina.servicedemo.DemoService");
        boolean ok=bindService(serviceIntent, mServiceConnection,Context.BIND_AUTO_CREATE);
        Log.v("ok", String.valueOf(ok));
    }

    private ServiceConnection mServiceConnection=new ServiceConnection() {

  @Override
  public void onServiceDisconnected(ComponentName name) {
   // TODO Auto-generated method stub

  }

  @Override
  public void onServiceConnected(ComponentName name, IBinder service) {
   // get instance of the aidl binder
   mRemoteService = IRemoteService.Stub.asInterface(service);
   try {
    String message=mRemoteService.sayHello("Mina");
    Log.v("message", message);
   } catch (RemoteException e) {
    Log.e("RemoteException", e.toString());
   }

  }
 };
}

and that's was all about calling remote services with AIDL.

Official Google Blog: When patents attack Android

2011-08-03T23:48:00.000+02:00

Official Google Blog: When patents attack Android

Android Story: From [x] cube Labs

2011-07-28T10:40:00.000+02:00

Infographic by Android Developers at [x]cubelabs

Symbyo Technologies: The Android Invasion Continues!!

2011-07-17T18:51:00.000+02:00

Symbyo Technologies: The Android Invasion Continues!!

Android Services

2011-07-05T19:22:00.003+02:00

Android Service is used for long-running processes that do not require user interaction, such as calling a web service and parsing response. Or processes that need to be running even if the application that started the service is not on the foreground such as playing mp3 files in a music player.

we need to distinguish between A Service and a Thread or an AsyncTask: Threads or Async task perform their tasks in a background thread thus they do not block the main thread, while a service performs it's work in the main thread. so if a service is performing an intensive task such as calling a web service, it may block the main thread until it finishes. So for intensive tasks a service should run it's work in a background thread.

A service runs in the same process of the application and keeps running until stopped by itself, stopped by the user or killed by the system if it needs memory.

Creating a service:

to create a service we create a class that extends android.app.Service and it would be like this:

public class DemoService extends Service {

 @Override
 public IBinder onBind(Intent arg0) {
  // TODO Auto-generated method stub
  return null;
 }

}

next we need to define our service in our AndroidManifest.xml file:

<service android:name="DemoService"></service>

The service life cycle has the following events

onCreate(): called when the service is created.
onStart(): Called when the service starts by a call to startService(Intent intent).
onDestroy(): Called as the service is terminates.

Calling a service:

A service can be called from an activity in two ways:

By calling startService(Intent intent).
By binding to the service through an Binder object.

calling startService(Intent intent):

to start a service from an activity using this method, we create an intent and start the service like this:

Intent intent=new Intent(this,DemoService.class);
startService(intent);

the startService(intent) method causes the onStart() method of the service to be called, so the service can execute it's work like this:

public class DemoService extends Service {

 @Override
 public IBinder onBind(Intent arg0) {
  // TODO Auto-generated method stub
  return null;
 }

 @Override
 public void onStart(Intent intent, int startId) {
  super.onStart(intent, startId);
  doSomething();
 }

 public void doSomething(){
  // do some work
 }

}

the service will keep running until it stops itself via stop stopSelf() after finishing work:

@Override
 public void onStart(Intent intent, int startId) {
  super.onStart(intent, startId);
  doSomething();
  stopSelf();
 }

or it can be stopped from the activity via stopService(Intent intent).

Binding to a service through an Binder object:

As the service runs in the same process of the application the service has only one instance (singleton) instance running. you may want to keep reference to this instance to perform periodical tasks or to call the service methods themselves.

to make the service bind-able we extends Binder class and return an instance of it in the service's onBind(Intent intent) method:

public class DemoService extends Service {

 private final IBinder binder = new LocalBinder();
 @Override
 public IBinder onBind(Intent arg0) {
  return binder;
 }

 public class LocalBinder extends Binder {
  DemoService getService() {
            return DemoService.this;
        }
    }

 @Override
 public void onStart(Intent intent, int startId) {
  super.onStart(intent, startId);
  doSomething();
  stopSelf();
 }

 public void doSomething(){
  // do something
 }

}

then we bind the service from our activity by first creating a ServiceConnection object to handle the service connection/disconnection then binding to the service by an intent like this:

public class MainActivity extends Activity {

 DemoService mService;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }

    ServiceConnection serviceConn=new ServiceConnection() {

                /**
                * service unbound, release from memory
                **/
  @Override
  public void onServiceDisconnected(ComponentName name) {
   mService=null;
  }

                /**
                * service is bound, start it's work
                **/
  @Override
  public void onServiceConnected(ComponentName name, IBinder service) {
   mService=((LocalBinder)service).getService();
   mService.doSomething();

  }
 };

    @Override
    protected void onResume() {
     super.onResume();
        // bind to the service by an intent
     Intent intent=new Intent(this,DemoService.class);
        // AUTO CREATE: creates the service and gives it an importance so that it won't be killed
        // unless any process bound to it (our activity in this case) is killed to
     bindService(intent, serviceConn, Context.BIND_AUTO_CREATE);
    }

    @Override
    protected void onDestroy() {
     super.onDestroy();
        / unbind the service whena ctivity is destroyed
     unbindService(serviceConn);
    }
}

notice that we unbind the service in the activity's onDestroy() method to disconnect from the service and stop it from executing any further

and that's was all about Android services, stay tuned for another Android tutorial.

Parsing JSON respone:

2011-07-04T19:19:00.005+02:00

if we have a JSON web service response like this:

"persons"
[
{
"person"{
"firstName": "John",
     "lastName": "Smith",
     "age": 25
}
}
{
"person"{
"firstName": "Catherine",
     "lastName": "Jones",
     "age": 35
}
}
]

this response is a JSON Array with the name "persons", this array consists of "person" JSON Objects.
to parse such a reponse:

public ArrayList<Person> getMessage(String response){
  JSONObject jsonResponse;
  ArrayList<Person> arrPersons=new ArrayList<Person>;
  try {
   // obtain the reponse
   jsonResponse = new JSONObject(response);
   // get the array
   JSONArray persons=jsonResponse.optJSONArray("persons");
   // iterate over the array and retrieve single person instances
   for(int i=0;i<persons.length();i++){
    // get person object
    JSONObject person=persons.getJSONObject(i);
    // get first name
    String firstname=person.optString("firstname");
    // get last name
    String lastname=person.optString("lastname");
    // get the age
    int age=person.optInt("age");

    // construct the object and add it to the arraylist
    Person p=new Person();
    p.firstName=firstname;
    p.lastName=lastname;
    p.age=age;
    arrPersons.add(p);
   }

  } catch (JSONException e) {

   e.printStackTrace();
  }

  return arrPersons;
 }

notice that we used the methods optJSONArray,optString,optInt instead of using getString,getInt because the opt methods return empty strings or zero integers if no elements are found. while the get methods throw an exception if the element is not found.