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Android Application Development Tutorial. Accessing Sensors and the Network. Background Introduction to Android Overview of Sensors Programming Tutorial 1: Tracking location with GPS and Google Maps Overview of Networking Programming Tutorial 2: Downloading from the Internet

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Android Application Development Tutorial

Accessing Sensors and the Network


  • Background

  • Introduction to Android

  • Overview of Sensors

  • Programming Tutorial 1: Tracking location with GPS and Google Maps

  • Overview of Networking

  • Programming Tutorial 2: Downloading from the Internet

  • Programming Tutorial 3: Sending/Receiving SMS Messages

  • Questions/Comments

  • Resources

Topics


Introduction to Android

A brief guide to the Android Application Development Environment


  • Software platform from Google and the Open Handset Alliance

  • July 2005, Google acquired Android, Inc.

  • November 2007, Open Handset Alliance formed to develop open standards for mobile devices

  • October 2008, Android available as open source

  • December 2008, 14 new members joined Android project

Background


  • April 30, 2009: Official 1.5 Cupcake release

  • September 15, 2009: 1.6 SDK Donut release

  • October 26, 2009: 2.0 SDK Éclair release

    • Updates to the Éclair release:

      • 2.0.1 on December 3, 2009

      • 2.1 on January 12, 2010

Update History


Platform Versions


  • Built-in Apps ≡ Apps created in SDK

  • Leverage Linux kernel to interface with hardware

  • Open source platform promotes development from global community

Android and the Hardware


  • Reuse and replacement of components

  • Dalvik virtual machine

  • Integrated browser

  • Optimized graphics

  • SQLite

  • Media support

  • GSM Telephony

  • Bluetooth, EDGE, 3G, and WiFi

  • Camera, GPS, compass, and accelerometer

  • Rich development environment

Android Features


Android Architecture


  • Apps are written in Java

  • Bundled by Android Asset Packaging Tool

  • Every App runs its own Linux process

  • Each process has it’s own Java Virtual Machine

  • Each App is assigned a unique Linux user ID

  • Apps can share the same user ID to see each other’s files

Application Fundamentals


  • Activity

    • Present a visual user interface for one focused endeavor the user can undertake

    • Example: a list of menu items users can choose from

  • Services

    • Run in the background for an indefinite period of time

    • Example: calculate and provide the result to activities that need it

  • Broadcast Receivers

    • Receive and react to broadcast announcements

    • Example: announcements that the time zone has changed

  • Content Providers

    • Store and retrieve data and make it accessible to all applications

    • Example: Android ships with a number of content providers for common data types (e.g., audio, video, images, personal contact information, etc.)

  • Intents

    • Hold the content of a message

    • Example: convey a request for an activity to present an image to the user or let the user edit some text

Application Components


  • http://developer.android.com/sdk/installing.html

  • Preparing your system and system requirements

  • Downloading and Installing the SDK

  • Installing ADT plug-in for Eclipse

  • Adding Platforms and Components

  • Exploring the SDK

  • Completing tutorials

  • Troubleshooting

Installation


Overview of Sensors

The Android Sensor Platform and how to use it


  • Developer’s are able to access “goodies”

  • Hardware capabilities made available

Open Source Platform


Hardware-oriented Features


  • Sensor type (Sensor class)

    • Orientation, accelerometer, light, magnetic field, proximity, temperature, etc.

  • Sampling rate

    • Fastest, game, normal, user interface.

    • When an application requests a specific sampling rate, it is really only a hint, or suggestion, to the sensor subsystem. There is no guarantee of a particular rate being available.

  • Accuracy

    • High, low, medium, unreliable.

Sensor and SensorManager


Programming Tutorial

Simulating an Android application that accesses positioning sensors


  • Must have Eclipse IDE installed

  • Must have Android SDK installed

  • Must have knowledge of Java

  • Must have the external Google Maps library installed in your SDK environment. The Maps library is included with the Google APIs add-on, which you can install using the Android SDK and AVD Manager.

Preparing for the Tutorial


  • A Google Maps API key is required to integrate Google Maps into your Android application.

  • To apply for a key:

    • Locate the SDK debug certificate in the default folder of "C:\Documents and Settings\<username>\Local Settings\Application Data\Android". The filename of the debug keystore is debug.keystore.

    • Copy the debug.keystore file to a folder named C:\Android\.

    • Open the command window and navigate to C:\Program Files\Java\<JDK_version_number>\bin to locate the Keytool.exe.

    • Execute the following to extract the MD5 fingerprint:

      keytool.exe -list -alias androiddebugkey -keystore "C:\Android\debug.keystore" -storepass android -keypass android

    • Copy the MD5 certificate fingerprint and navigate your web browser to: http://code.google.com/android/maps-api-signup.html.

    • Follow the instructions on the page to complete the application and obtain the Google Maps key.

      For more information on using Google Maps in Android application development:

      http://mobiforge.com/developing/story/using-google-maps-android

Get a Google Maps API Key


  • Defines the system image and device settings used by the Emulator

  • To create an AVD in Eclipse:

    • Select Window > Android SDK and AVD Manager.

      The Android SDK and AVD Manager displays.

    • Make sure the entry for Virtual Devices is selected and click New.

      The Create new AVD window displays.

    • Enter a Name for the AVD.

    • Select Google APIs (API level 3) as the Target.

    • Click Create AVD.

    • Close the Android SDK and AVD Manager.

Create an Android Virtual Device (AVD)


  • To create the project in Eclipse:

    • Select File > New > Project.

    • Select Android Project in the Android folder and click Next.

    • Enter GPSSimulator as the Project Name.

    • Select Google APIs (Platform 1.5) as the Build Target.

    • Enter GPSSimulator as the Application name.

    • Enter com.android.gpssimulator as the Package name.

    • Enter GPSSimulator as the Activity name.

    • Click Finish.

Create the Android Project


The New Android Project


  • Add permissions for GPS

  • To modify the AndroidManifest.xml file:

    • Click on the res folder in the GPSSimulator project.

    • Double-click AndroidManifest.xml to display the GPSSimulator Manifest.

    • Enter the following lines before the application tag.

      <uses-permission android:name=“android.permission.ACCESS_FINE_LOCATION” />

    • Save the changes to the file.

Modify the AndroidManifest.xml File


public class GPSSimulator extends Activity

{

private LocationManager lm;

private LocationListenerlocationListener;

// Called when the activity is first created.

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

// use the LocationManager class to obtain GPS locations

lm = (LocationManager)

getSystemService(Context.LOCATION_SERVICE);

locationListener = new MyLocationListener();

lm.requestLocationUpdates(

LocationManager.GPS_PROVIDER, 0, 0, locationListener);

}

}

Add LocationManager to get Updates


private class MyLocationListener implements LocationListener {

@Override

public void onLocationChanged(Location loc) {

if (loc != null) {

Toast.makeText(getBaseContext(),

"Location changed : Lat: " + loc.getLatitude() +

" Lng: " + loc.getLongitude(),

Toast.LENGTH_SHORT).show();

}

}

@Override

public void onProviderDisabled(String provider) {

// TODO Auto-generated method stub

}

@Override

public void onProviderEnabled(String provider) {

// TODO Auto-generated method stub

}

@Override

public void onStatusChanged(String provider, int status, Bundle extras) {

// TODO Auto-generated method stub

}

}

Add MyLocationListener


  • To test in Eclipse:

    • Switch to DDMS view.

    • Find the Location Controls in the Emulator Control tab.

    • Click the GPX tab and click Load GPX.

    • Locate and select the GPX file.

    • Click Play to begin sending coordinates to the Emulator.

Test the GPSSimulator


  • Update the Manifest with two lines.

    <?xml version="1.0" encoding="utf-8"?>

    <manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="com.android.GPSSimulator">

    <uses-permission

    android:name="android.permission.INTERNET" />

    <uses-permission

    android:name="android.permission.ACCESS_FINE_LOCATION" />

    <application android:icon="@drawable/icon"

    android:label="@string/app_name">

    <uses-library android:name="com.google.android.maps" />

    <activity android:name=".GPS" android:label="@string/app_name">

    <intent-filter>

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

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

    </intent-filter>

    </activity>

    </application>

    </manifest>

Add ability to use Google Maps


<?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"

>

<com.google.android.maps.MapView

android:id="@+id/mapview1"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:enabled="true"

android:clickable="true"

android:apiKey=“Your API Key Here" />

</LinearLayout>

Add MapView to main.xml


public class GPSSimulator extends MapActivity {

private LocationManager lm;

private LocationListenerlocationListener;

private MapViewmapView;

private MapController mc;

// Called when the activity is first created.

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

// use the LocationManager class to obtain GPS locations

lm = (LocationManager)

getSystemService(Context.LOCATION_SERVICE);

locationListener = new MyLocationListener();

lm.requestLocationUpdates(

LocationManager.GPS_PROVIDER, 0, 0, locationListener);

mapView = (MapView) findViewById(R.id.mapview1);

mc = mapView.getController();

}

@Override

protected booleanisRouteDisplayed() {

return false;

}

private class MyLocationListener implements LocationListener {

@Override

public void onLocationChanged(Location loc) {

if (loc != null) {

Toast.makeText(getBaseContext(),

"Location changed : Lat: " + loc.getLatitude() +

" Lng: " + loc.getLongitude(),

Toast.LENGTH_SHORT).show();

GeoPoint p = new GeoPoint(

(int) (loc.getLatitude() * 1E6),

(int) (loc.getLongitude() * 1E6));

mc.animateTo(p);

mc.setZoom(16);

mapView.invalidate();

}

}

@Override

public void onProviderDisabled(String provider) {

}

@Override

public void onProviderEnabled(String provider) {

}

@Override

public void onStatusChanged(String provider, int status, Bundle extras) {

}

}

}

Modify GPSSimulator to use Google Maps


View the Location on the Map


Internet Layers

  • The Internet, is based on a layered architecture called the TCP/IP stack.

  • Link Layer

    • Protocols: ARP and RARP

  • Internet Layer

    • Protocols: IP, ping, etc.

  • Transport

    • Protocols: TCP and UDP

  • Application Layer

    • Protocols: HTTP, FTP, DNS, etc.


  • A server machine is identified on the Internet by some IP address

  • Daemons are the processes running in the background which are listening all the time for connection requests from clients on a particular port number.

  • Once a connection request comes into the server on a given port, the corresponding daemon can choose to accept it, and if so, a connection is established.

  • Then the application layer protocol is typically used for the client to get or send data to the server.

Client-Server Communication


Programming Tutorial 2

Accessing a website from the Android Emulator


Required Packages


Layout


  • View object may have an integer ID associated with it

    android:id="@+id/my_button“

  • To get the reference of the view object in activity

    Button myButton = (Button)findViewById(R.id.my_button);

Link Activity and View


  • View.OnClickListener()

    • Interface definition for a callback to be invoked when a view is clicked. 

  • onClick(View v)

    • Called when a view has been clicked. Inside this function you can specify what actions to perform on a click.

Adding Event to View Object


Strings.xml


AndroidManifest.xml


  • If you are using the emulator then there are limitations. Each instance of the emulator runs behind a virtual router/firewall service that isolates it from your development machine's network interfaces and settings and from the internet.

  • Communication with the emulated device may be blocked by a firewall program running on your machine.

  • Reference

Network Settings


Behind Proxy Server


Behind Proxy Server


Behind Proxy Server


Behind Proxy Server


Behind Proxy Server


Behind Proxy Server


  • Step1 Add permissions to AndroidManifest.xml

    <uses-permission android:name="android.permission.INTERNET" />

  • Step 2 Import files

    import java.io.IOException;

    import java.io.InputStream;

    import java.io.InputStreamReader;

    import java.net.HttpURLConnection;

    import java.net.URL;

    import java.net.URLConnection;

    import android.app.Activity;

    import android.graphics.Bitmap;

    import android.graphics.BitmapFactory;

    import android.os.Bundle;

    import android.widget.ImageView;

    import android.widget.TextView;

    import android.widget.Toast;

App to Download jpg file


  • Step 3 Writing OpenHttpConnection()

    • To open a connection to a HTTP server using OpenHttpConnection()

    • We first create an instance of the URL class and initialize it with the URL of the server

    • When the connection is established, you pass this connection to an URLConnection object. To check if the connection established is using a HTTP protocol.

    • The URLConnection object is then cast into an HttpURLConnection object and you set the various properties of the HTTP connection.

    • Next, you connect to the HTTP server and get a response from the server. If the response code is HTTP_OK, you then get the InputStream object from the connection so that you can begin to read incoming data from the server

    • The function then returns the InputStream object obtained.

App to Download jpg file


public class HttpDownload extends Activity {

/** Called when the activity is first created.*/

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

}

private InputStream OpenHttpConnection(String urlString) throws IOException {

InputStream in = null;

int response = -1;

URL url = new URL(urlString);

URLConnection conn = url.openConnection();

if (!(conn instanceof HttpURLConnection))

throw new IOException("Not an HTTP connection");

try{

HttpURLConnection httpConn = (HttpURLConnection) conn;

httpConn.setAllowUserInteraction(false);

httpConn.setInstanceFollowRedirects(true);

httpConn.setRequestMethod("GET");

httpConn.connect();

response = httpConn.getResponseCode();

if (response == HttpURLConnection.HTTP_OK) {

in = httpConn.getInputStream();

}

} catch (Exception ex) {

throw new IOException("Error connecting");

}

return in;

}

}

App to Download jpg file


  • Step 4 Modify the Main.xml code

    <?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"

    >

    <ImageView

    android:id="@+id/img"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:layout_gravity="center"

    />

    <TextView

    android:id="@+id/text"

    android:textStyle="bold"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    />

    </LinearLayout>

App to Download jpg file


  • Step 5 writing DownloadImage()

    • The DownloadImage() function takes in a string containing the URL of the image to download.

    • It then calls the OpenHttpConnection() function to obtain an InputStream object for reading the image data.

    • The InputStream object is sent to the decodeStream() method of the BitmapFactory class.

    • The decodeStream() method decodes an InputStream object into a bitmap.

    • The decoded bitmap is then returned by the DownloadImage() function.

private Bitmap DownloadImage(String URL) {

Bitmap bitmap = null;

InputStream in = null;

try {

in = OpenHttpConnection(URL);

bitmap = BitmapFactory.decodeStream(in);

in.close();

} catch (IOException e1) {

e1.printStackTrace();

}

return bitmap;

}

App to Download jpg file


  • Step 6 Test the DownloadImage() function, modify the onCreate() event as follows

    @Override

    public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.main);

    Bitmap bitmap = DownloadImage(

    "http://www.streetcar.org/mim/cable/images/cable-01.jpg");

    img = (ImageView) findViewById(R.id.img);

    img.setImageBitmap(bitmap);

    }


  • Step 7:Output

App to Download jpg file


Programming Tutorial 3

Transmitting SMS messages across the network


  • Intents request for an action to be performed and supports interaction among the Android components.

    • For an activity it conveys a request to present an image to the user

    • For broadcast receivers, the Intent object names the action being announced.

  • Intent Filter Registers Activities, Services and Broadcast Receivers(as being capable of performing an action on a set of data).

Intent and IntentFilter


  • STEP 1

    • In the AndroidManifest.xml file, add the two permissions - SEND_SMS and RECEIVE_SMS.

  • STEP 2

    • In the main.xml, add Text view to display "Enter the phone number of recipient“ and "Message"

    • EditText with id txtPhoneNo and txtMessage

    • Add the button ID "Send SMS“

SMS Sending


  • Step 3 Import Classes and Interfaces

  • import android.app.Activity;

  • import android.app.PendingIntent;

  • import android.content.Intent;

  • import android.os.Bundle;

  • import android.telephony.SmsManager;

  • import android.view.View;

  • import android.widget.Button;

  • import android.widget.EditText;

  • import android.widget.Toast;

SMS Sending


  • Step 4 Write the SMS class

    public class SMS extends Activity {

    Button btnSendSMS;

    EditTexttxtPhoneNo;

    EditTexttxtMessage;

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.main);

    btnSendSMS = (Button) findViewById(R.id.btnSendSMS);

    txtPhoneNo = (EditText) findViewById(R.id.txtPhoneNo);

    txtMessage = (EditText) findViewById(R.id.txtMessage);

    btnSendSMS.setOnClickListener(new View.OnClickListener() {

    public void onClick(View v) {

    String phoneNo = txtPhoneNo.getText().toString();

    String message = txtMessage.getText().toString();

    if (phoneNo.length()>0 && message.length()>0)

    sendSMS(phoneNo, message);

    else

    Toast.makeText(getBaseContext(),

    "Please enter both phone number and message.",

    Toast.LENGTH_SHORT).show();

    }

    });

    }

    }

Input from the user (i.e., the phone no, text message and sendSMS is implemented).

SMS Sending


  • Step 5

    • To send an SMS message, you use the SmsManager class. And to instantiate this class call getDefault() static method.

    • The sendTextMessage() method sends the SMS message with a PendingIntent.

    • The PendingIntent object is used to identify a target to invoke at a later time.

      private void sendSMS(String phoneNumber, String message) {

      PendingIntent pi = PendingIntent.getActivity(this, 0,

      new Intent(this, SMS.class), 0);

      SmsManagersms = SmsManager.getDefault();

      sms.sendTextMessage(phoneNumber, null, message, pi, null);

      }

SMS Sending


SMS Sending


  • Step 1

Receiving SMS


  • Step 2

    • In the AndroidManifest.xml file add the <receiver> element so that incoming SMS messages can be intercepted by the SmsReceiver class.

      <receiver android:name=".SmsReceiver">

      <intent-filter>

      <action android:name=

      "android.provider.Telephony.SMS_RECEIVED" />

      </intent-filter>

      </receiver>

Receiving SMS


  • Step 3

    import android.content.BroadcastReceiver;

    import android.content.Context;

    import android.content.Intent;

    import android.telephony.SmsMessage;

    import android.widget.Toast;

Receiving SMS


  • Step 4

    public class SmsReceiver extends BroadcastReceiver {

    @Override

    public void onReceive(Context context, Intent intent) {

    //---get the SMS message passed in---

    Bundle bundle = intent.getExtras();

    SmsMessage[] msgs = null;

    String str = "";

    if (bundle != null){

    //---retrieve the SMS message received---

    Object[] pdus = (Object[]) bundle.get("pdus");

    msgs = new SmsMessage[pdus.length];

    for (inti=0; i<msgs.length; i++) {

    msgs[i] = SmsMessage.createFromPdu((byte[])pdus[i]);

    str += "SMS from " + msgs[i].getOriginatingAddress();

    str += " :";

    str += msgs[i].getMessageBody().toString();

    str += "\n";

    }

    //---display the new SMS message---

    Toast.makeText(context, str, Toast.LENGTH_SHORT).show();

    }

    }

    }

In the SmsReceiver class, extend the BroadcastReceiver class and override the onReceive() method. The message is attached to the Intent

The messages are stored in a object array PDU format. To extract each message, you use the static createFromPdu() method from the SmsMessage class. The SMS message is then displayed using the Toast class

Receiving SMS


Receiving SMS


  • What is Android?

  • What are the sensor and networking capabilities in Android?

  • How to use location data and Google maps in Android?

  • How to access websites?

  • How to send SMS messages across the network?

  • Questions/Comments?

Conclusions


  • Ableson, Frank. “Tapping into Android’s sensors.” www.ibm.com. January 30, 2010. http://www.ibm.com/developerworks/opensource/library/os-android-sensor/index.html

  • Ableson, Frank; Collins, Charlie; Sen, Robi. Unlocking Android, A Developer’s Guide. Greenwich: Manning Publications Co. 2009.

  • Android Development Guide. January 30, 2010. http://developer.android.com/guide/index.html

  • Lee, Wei-Meng. “Using Google Maps in Android.” mobiforge.com. January 30, 2010. http://mobiforge.com/developing/story/using-google-maps-android

  • Lee, Wei-Meng. “You Are Here: Using GPS and Google Maps in Android.” www.devx.com. January 30, 2010. http://www.devx.com/wireless/Article/39239/1954

  • Lee, Wei-Meng “SMS Messaging in Android” mobiforge.com. January 30, 2010

  • http://mobiforge.com/developing/story/sms-messaging-android

  • Lee, Wei-Meng “Connecting to the Web: I/O Programming in Android” November 5, 2008   Android”http://www.devx.com/wireless/Article/39810

  • Open Handset Alliance, http://www.openhandsetalliance.com/

  • Patterson, Don. “Android Development Guide.” getsatisfaction.com. January 30, 2010. http://getsatisfaction.com/luci/topics/android_development_guide

  • www.androidcompetencycenter.com. January 30, 2010. http://www.androidcompetencycenter.com/2009/06/accessing-device-sensors

  • XianhuaShu; Zhenjun Du; Rong Chen, "Research on Mobile Location Service Design Based on Android," Wireless Communications, Networking and Mobile Computing, 2009. WiCom '09. 5th International Conference on , vol., no., pp.1-4, 24-26 Sept. 2009http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=5302615&isnumber=5300799

Resources


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