eclipse_newsletter/2013/march/content/en_article2.php - gerrit/www.eclipse.org/community - Git at Google

 <?php
 /*******************************************************************************
  * Copyright (c) 2015 Eclipse Foundation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  *    Eric Poirier (Eclipse Foundation) - Initial implementation
  *******************************************************************************/
 ?>

 <h1 class="article-title"><?php echo $pageTitle; ?></h1>

     <p>
       Android is an amazing operating system that combines technical
       innovation with high popularity among the end-consumers. In spite
       of fragmentation, there is a large amount of developers across the
       world who enjoy developing applications for Android. Today, most
       Android applications are written in Java. Unfortunately, Java is
       known to be deficient in some modern language concepts and idioms
       like conciseness, declarativity, modularity mechanisms, the
       map/reduce pattern or immutable data. Wouldn't it be great if
       there was a more advanced programming language for Android
       development? Luckily, there is one and it integrates seamlessly
       with Java. This language is <a href="http://www.eclipse.org/xtend">Xtend</a>.
     </p>
     <p>
       Xtend is a statically-typed programming language that compiles to
       Java. Xtend has a clear and concise syntax. Although lambda
       expressions will be finally introduced in Java 8, Xtend's syntax
       for them is significantly more readable. Another feature that
       makes Xtend a functional language is the absence of statements.
       Code written in Xtend is executed by evaluating expressions.
       Operator overloading in form of an operator-to-method mapping
       allows to fully customize operator semantics. Extension methods
       enhance existing types with new functionality. Other powerful
       features like the type-based switch expression, shorthand property
       access and local type inference make programming in Xtend real
       fun. Even more important than the language features is the
       seamless, bidirectional interoperability with Java, a low learning
       curve for Java developers, comprehensible and efficient generated
       Java source code and the great IDE support. All this makes Xtend
       ready for immediate use in every environment where Java and
       Eclipse are used for development. If you are new to Xtend, check
       out its <a href="http://www.eclipse.org/xtend/documentation.html">documentation</a>.
     </p>
     <p>
       In this tutorial, we will write an Android application in Xtend,
       build an APK and run it on the Android emulator. We will implement
       a simple application called <i>Is Following?</i> which lets us
       check if a Twitter user follows another Twitter user.
     </p>
     <img
       src="/community/eclipse_newsletter/2013/march/images/android_screenshot1.jpg"
       alt="Screenshot of the app 'Is Following?'" />
     <p>To be able to follow the tutorial, you need to be acquainted with
       Android development and the Eclipse IDE.</p>
     <h3>Setting Up The IDE</h3>
     <p>First, we'll install and configure the IDE and create a project.
       You can skip the first three steps, if you already have an Eclipse
       installation that you use for Android development.</p>
     <ul>
       <li>Download and install Eclipse IDE with built-in Android
         Developer Tools from <a
         href="http://developer.android.com/sdk/index.html">http://developer.android.com/sdk/index.html</a>.


       <li>Follow the instructions at <a
         href="http://developer.android.com/sdk/installing/bundle.html">http://developer.android.com/sdk/installing/bundle.html</a>
         to set up your Android SDK for the first time.

       <li>Alternatively, you can use an existing Eclipse installation
         and set it up as described at <a
         href="http://developer.android.com/sdk/installing/index.html">http://developer.android.com/sdk/installing/index.html</a>.


       <li>After you have Eclipse, the Android SDK and the ADT plugin
         ready, install version 2.4 of Xtend. To do so, go to Help ->
         Install New Softwareâ€¦ and paste the Xtend update site <a
         href="http://download.eclipse.org/modeling/tmf/xtext/updates/composite/releases">http://download.eclipse.org/modeling/tmf/xtext/updates/composite/releases</a>
         into the field labeled <i>Work with</i>.

       <li>Choose Xtend 2.4.

       <li>Disable the checkbox <i>Contact all update sites during
           install to find required software</i>, to avoid unwanted
         updates of other Eclipse plug-ins.

       <li>Click <i>Finish</i> and follow the instructions of the
         installation wizard.

     </ul>

     <h3>Creating A Project</h3>
     <p>
       Now, we'll create a project and start writing the application. You
       can download the complete source code from <a
         href="https://github.com/nossipova/isfollowing">https://github.com/nossipova/isfollowing</a>.
     </p>


     <ul>
       <li><p>Create a new Android Application Project with a blank
           activity MainActivity.</p> <img
         src="/community/eclipse_newsletter/2013/march/images/android_screenshot2.jpg"
         alt="New Android project" />

       <li>The compiler compliance level of the project needs to be set
         to 1.6.

     </ul>
     <h3>Creating A Layout</h3>
     <p>Create a simple layout that consists of:</p>
     <ul>
       <li>an editable field for each of both Twitter names,

       <li>a button to start the request and

       <li><p>a text view that will show a result.</p> <img
         src="/community/eclipse_newsletter/2013/march/images/android_screenshot3.jpg"
         alt="The Layout" />

     </ul>


     <h3>Writing The Application</h3>
     <p>Our application will have an activity to interact with the user
       and a communicator which will send requests to Twitter and process
       its responses. The communication with Twitter will be performed
       asynchronously. Let's implement these components.</p>


     <ul>
       <li>Delete the class <code>MainActivity.java</code> that was
         automatically generated through the project creation.

       <li>To create a new Xtend class, select <i>New -> Xtend Class</i>
         from the project context menu in the <i>Package Explorer</i>.

       <li>On the first page of the creation wizard, type <code>MainActivity</code>
         in the <i>Name</i> field and select <code>android.app.Activity</code>
         as a superclass.

       <li>Click <i>Finish</i>.

       <li><p>The class we've just created will show an error:

         <pre>
 Mandatory library bundle 'org.eclipse.xtext.xbase.lib' 2.3.0 or higher not found on the classpath.
 </pre> Use the available quick fix to add Xtend libraries to the
         classpath.

       <li><p>
           <code>MainActivity</code>
           will have two methods:
           <code>onCreate(Bundle)</code>
           and
           <code>showResult(Object)</code>
           . The first method
           <code>onCreate(Bundle)</code>
           prepares the content view and registers the click listener
           callback of the <i>Check</i> button. In the callback, we
           initialize the communicator, use its method
           <code>isNetworkAvailable(Context)</code>
           to test the connectivity and execute the communicator
           asynchronously. The second method
           <code>showResult(Object)</code>
           updates the UI with the response received from the
           communicator by setting the text value in the result text
           view.
         </p> <pre class="prettyprint lang-xtend">
 package de.nataliaossipova.isfollowing

 import android.app.Activity
 import android.os.Bundle
 import android.view.View
 import android.widget.Button
 import android.widget.EditText
 import android.widget.TextView

 import static de.nataliaossipova.isfollowing.R$id.*
 import static de.nataliaossipova.isfollowing.R$layout.*
 import static de.nataliaossipova.isfollowing.R$string.*

 class MainActivity extends Activity implements AsyncDelegate {

     override onCreate(Bundle it) {
       super.onCreate(it)
       contentView = activity_main

       val Button button = getView(Button01)
       button.onClickListener = [
         var communicator = new TwitterCommunicator
         communicator.delegate = this
         if (communicator.isNetworkAvailable(this)) {
           val EditText editText1 = getView(EditText01)
           val EditText editText2 = getView(EditText02)
           communicator.execute(editText1.text.toString, editText2.text.toString)
         }
       ]
     }

     override showResult(Object it) {
       var TextView resultView = getView(ResultView)
       resultView.text = if ('true' == it) {
           getString(yes).toUpperCase
         } else {
           getString(no).toUpperCase
         }
     }

     def &lt;T extends View&gt; T getView(int id) {
       findViewById(id) as T
     }
 }
 </pre>

       <li><p>
           Create a new Xtend class
           <code>TwitterCommunicator</code>
           as a subclass of
           <code>android.os.AsyncTask</code>
           . The subclass implements two methods:
           <code>doInBackground(Params...)</code>
           and
           <code>onPostExecute(Result)</code>
           . In
           <code>doInBackground(Paramsâ€¦)</code>
           method, we create a new Twitter URL from both Twitter names
           passed in as parameters. After that, we open an HTTP
           connection and read the input stream from it. The second
           method passes the data read from the input stream to the main
           activity.

         <pre class="prettyprint lang-xtend">
 package de.nataliaossipova.isfollowing

 import android.content.Context
 import android.net.ConnectivityManager
 import android.os.AsyncTask
 import com.google.common.io.CharStreams
 import java.io.InputStream
 import java.io.InputStreamReader
 import java.net.URL

 class TwitterCommunicator extends AsyncTask&lt;String, Void, String&gt; {

     AsyncDelegate delegate

     override protected doInBackground(String... params) {
         new URL('https://api.twitter.com/1/friendships/exists.json?screen_name_a='
                   + params.get(0) + '&amp;screen_name_b=' + params.get(1))
                  .openConnection.inputStream.readStream
     }

     override onPostExecute(String result) {
         if (delegate != null) {
             delegate.showResult(result)
         }
     }

     def setDelegate(AsyncDelegate delegate) {
         this.delegate = delegate
     }

     def isNetworkAvailable(Context it) {
         val networkInfo = (getSystemService(Context::CONNECTIVITY_SERVICE)
         as ConnectivityManager).activeNetworkInfo
         return networkInfo != null &amp;&amp; networkInfo.connected
     }

     def private readStream(InputStream in) {
       return CharStreams::toString(new InputStreamReader(in))
     }
 }
 </pre>


       <li><p>
           To avoid tight coupling between the activity and the
           communicator, we will make use of the delegate pattern. Create
           a new Xtend interface
           <code>AsyncDelegate</code>
           . The interface declares only one method
           <code>showResult(Object)</code>
           . We will call this method from the post execute callback of
           <code>TwitterCommunicator</code>
           .

         <pre class="prettyprint lang-xtend">
 package de.nataliaossipova.isfollowing

 interface AsyncDelegate {
     def void showResult(Object it)
 }
 </pre></li></ul>
  <p>The <code>MainActivity</code> already implements the <code>AsyncDelegate</code>
         interface.
         </p>
         <h3>Build And Run</h3>
         <p>
           Now, when we are done with writing source code, add
           permissions
           <code>android.permission.INTERNET</code>
           and
           <code>android.permission.ACCESS_NETWORK_STATE</code>
           to the Android manifest and let's build an APK and run it on
           an AVD.
         </p>
         <p>
           We need to tell ADT how to export the Xtend libraries. Choose
           <i>Properties -> Java Build Path</i> from the project context
           menu and go to the <i>Order and Export</i> tab. Select the
           checkbox beside <i>Xtend library</i>.
         </p> <img
         src="/community/eclipse_newsletter/2013/march/images/android_screenshot4.jpg"
         alt="New Android project" />
         <p>After closing the Properties window, you can launch the
           application on an existing AVD or a device.</p>
         <h3>Where To Go From Here</h3>

         <p>Now that you know how to use Xtend for Android development,
           go and create awesome Android apps in this sophisticated
           programming language!</p>

         <p>Don't hesitate to let me know if anything of the above is
           confusing to you or if you'd like me to go into more detail.</p>
         <script
           src="http://www.eclipse.org/xtend/google-code-prettify/prettify.js"
           type="text/javascript"></script> <script
           src="http://www.eclipse.org/xtend/google-code-prettify/lang-xtend.js"
           type="text/javascript"></script> <script
           type="text/javascript">
   prettyPrint();
 </script>


 <div class="bottomitem">
   <h3>About the Authors</h3>

   <div class="row">
     <div class="col-sm-12">
       <div class="row">
         <div class="col-sm-8">
           <img class="author-picture"
         src="/community/eclipse_newsletter/2013/march/images/natalia_ossipova1.jpg"
         alt="Natalia Ossipova" />
         </div>
         <div class="col-sm-16">
           <p class="author-name">
         Natalia Ossipova <br /> <a
           href="http://nataliaossipova.wordpress.com/">Freelance
           Software Architect</a>
       </p>
       <ul class="author-link">
         <li><a href="http://nataliaossipova.wordpress.com/">Blog</a></li>
         <li><a href="https://twitter.com/nossipova">Twitter</a></li>
         <li><a href="http://www.linkedin.com/in/nataliaossipova">LinkedIn</a></li>
         <li><a href="<?php echo $original_url; ?>">Original Article</a></li>
       </ul>
         </div>
       </div>
     </div>
   </div>
 </div>
	<?php
	/*******************************************************************************
	* Copyright (c) 2015 Eclipse Foundation and others.
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License v1.0
	* which accompanies this distribution, and is available at
	* http://eclipse.org/legal/epl-v10.html
	*
	* Contributors:
	* Eric Poirier (Eclipse Foundation) - Initial implementation
	*******************************************************************************/
	?>

	<h1 class="article-title"><?php echo $pageTitle; ?></h1>

	<p>
	Android is an amazing operating system that combines technical
	innovation with high popularity among the end-consumers. In spite
	of fragmentation, there is a large amount of developers across the
	world who enjoy developing applications for Android. Today, most
	Android applications are written in Java. Unfortunately, Java is
	known to be deficient in some modern language concepts and idioms
	like conciseness, declarativity, modularity mechanisms, the
	map/reduce pattern or immutable data. Wouldn't it be great if
	there was a more advanced programming language for Android
	development? Luckily, there is one and it integrates seamlessly
	with Java. This language is <a href="http://www.eclipse.org/xtend">Xtend</a>.
	</p>
	<p>
	Xtend is a statically-typed programming language that compiles to
	Java. Xtend has a clear and concise syntax. Although lambda
	expressions will be finally introduced in Java 8, Xtend's syntax
	for them is significantly more readable. Another feature that
	makes Xtend a functional language is the absence of statements.
	Code written in Xtend is executed by evaluating expressions.
	Operator overloading in form of an operator-to-method mapping
	allows to fully customize operator semantics. Extension methods
	enhance existing types with new functionality. Other powerful
	features like the type-based switch expression, shorthand property
	access and local type inference make programming in Xtend real
	fun. Even more important than the language features is the
	seamless, bidirectional interoperability with Java, a low learning
	curve for Java developers, comprehensible and efficient generated
	Java source code and the great IDE support. All this makes Xtend
	ready for immediate use in every environment where Java and
	Eclipse are used for development. If you are new to Xtend, check
	out its <a href="http://www.eclipse.org/xtend/documentation.html">documentation</a>.
	</p>
	<p>
	In this tutorial, we will write an Android application in Xtend,
	build an APK and run it on the Android emulator. We will implement
	a simple application called <i>Is Following?</i> which lets us
	check if a Twitter user follows another Twitter user.
	</p>
	<img
	src="/community/eclipse_newsletter/2013/march/images/android_screenshot1.jpg"
	alt="Screenshot of the app 'Is Following?'" />
	<p>To be able to follow the tutorial, you need to be acquainted with
	Android development and the Eclipse IDE.</p>
	<h3>Setting Up The IDE</h3>
	<p>First, we'll install and configure the IDE and create a project.
	You can skip the first three steps, if you already have an Eclipse
	installation that you use for Android development.</p>
	<ul>
	<li>Download and install Eclipse IDE with built-in Android
	Developer Tools from <a
	href="http://developer.android.com/sdk/index.html">http://developer.android.com/sdk/index.html</a>.




	<li>Follow the instructions at <a
	href="http://developer.android.com/sdk/installing/bundle.html">http://developer.android.com/sdk/installing/bundle.html</a>
	to set up your Android SDK for the first time.

	<li>Alternatively, you can use an existing Eclipse installation
	and set it up as described at <a
	href="http://developer.android.com/sdk/installing/index.html">http://developer.android.com/sdk/installing/index.html</a>.




	<li>After you have Eclipse, the Android SDK and the ADT plugin
	ready, install version 2.4 of Xtend. To do so, go to Help ->
	Install New Softwareâ€¦ and paste the Xtend update site <a
	href="http://download.eclipse.org/modeling/tmf/xtext/updates/composite/releases">http://download.eclipse.org/modeling/tmf/xtext/updates/composite/releases</a>
	into the field labeled <i>Work with</i>.

	<li>Choose Xtend 2.4.

	<li>Disable the checkbox <i>Contact all update sites during
	install to find required software</i>, to avoid unwanted
	updates of other Eclipse plug-ins.

	<li>Click <i>Finish</i> and follow the instructions of the
	installation wizard.

	</ul>

	<h3>Creating A Project</h3>
	<p>
	Now, we'll create a project and start writing the application. You
	can download the complete source code from <a
	href="https://github.com/nossipova/isfollowing">https://github.com/nossipova/isfollowing</a>.
	</p>



	<ul>
	<li><p>Create a new Android Application Project with a blank
	activity MainActivity.</p> <img
	src="/community/eclipse_newsletter/2013/march/images/android_screenshot2.jpg"
	alt="New Android project" />

	<li>The compiler compliance level of the project needs to be set
	to 1.6.

	</ul>
	<h3>Creating A Layout</h3>
	<p>Create a simple layout that consists of:</p>
	<ul>
	<li>an editable field for each of both Twitter names,

	<li>a button to start the request and

	<li><p>a text view that will show a result.</p> <img
	src="/community/eclipse_newsletter/2013/march/images/android_screenshot3.jpg"
	alt="The Layout" />

	</ul>


	<h3>Writing The Application</h3>
	<p>Our application will have an activity to interact with the user
	and a communicator which will send requests to Twitter and process
	its responses. The communication with Twitter will be performed
	asynchronously. Let's implement these components.</p>


	<ul>
	<li>Delete the class <code>MainActivity.java</code> that was
	automatically generated through the project creation.

	<li>To create a new Xtend class, select <i>New -> Xtend Class</i>
	from the project context menu in the <i>Package Explorer</i>.

	<li>On the first page of the creation wizard, type <code>MainActivity</code>
	in the <i>Name</i> field and select <code>android.app.Activity</code>
	as a superclass.

	<li>Click <i>Finish</i>.

	<li><p>The class we've just created will show an error:

	<pre>
	Mandatory library bundle 'org.eclipse.xtext.xbase.lib' 2.3.0 or higher not found on the classpath.
	</pre> Use the available quick fix to add Xtend libraries to the
	classpath.

	<li><p>
	<code>MainActivity</code>
	will have two methods:
	<code>onCreate(Bundle)</code>
	and
	<code>showResult(Object)</code>
	. The first method
	<code>onCreate(Bundle)</code>
	prepares the content view and registers the click listener
	callback of the <i>Check</i> button. In the callback, we
	initialize the communicator, use its method
	<code>isNetworkAvailable(Context)</code>
	to test the connectivity and execute the communicator
	asynchronously. The second method
	<code>showResult(Object)</code>
	updates the UI with the response received from the
	communicator by setting the text value in the result text
	view.
	</p> <pre class="prettyprint lang-xtend">
	package de.nataliaossipova.isfollowing

	import android.app.Activity
	import android.os.Bundle
	import android.view.View
	import android.widget.Button
	import android.widget.EditText
	import android.widget.TextView

	import static de.nataliaossipova.isfollowing.R$id.*
	import static de.nataliaossipova.isfollowing.R$layout.*
	import static de.nataliaossipova.isfollowing.R$string.*

	class MainActivity extends Activity implements AsyncDelegate {

	override onCreate(Bundle it) {
	super.onCreate(it)
	contentView = activity_main

	val Button button = getView(Button01)
	button.onClickListener = [
	var communicator = new TwitterCommunicator
	communicator.delegate = this
	if (communicator.isNetworkAvailable(this)) {
	val EditText editText1 = getView(EditText01)
	val EditText editText2 = getView(EditText02)
	communicator.execute(editText1.text.toString, editText2.text.toString)
	}
	]
	}

	override showResult(Object it) {
	var TextView resultView = getView(ResultView)
	resultView.text = if ('true' == it) {
	getString(yes).toUpperCase
	} else {
	getString(no).toUpperCase
	}
	}

	def <T extends View> T getView(int id) {
	findViewById(id) as T
	}
	}
	</pre>

	<li><p>
	Create a new Xtend class
	<code>TwitterCommunicator</code>
	as a subclass of
	<code>android.os.AsyncTask</code>
	. The subclass implements two methods:
	<code>doInBackground(Params...)</code>
	and
	<code>onPostExecute(Result)</code>
	. In
	<code>doInBackground(Paramsâ€¦)</code>
	method, we create a new Twitter URL from both Twitter names
	passed in as parameters. After that, we open an HTTP
	connection and read the input stream from it. The second
	method passes the data read from the input stream to the main
	activity.

	<pre class="prettyprint lang-xtend">
	package de.nataliaossipova.isfollowing

	import android.content.Context
	import android.net.ConnectivityManager
	import android.os.AsyncTask
	import com.google.common.io.CharStreams
	import java.io.InputStream
	import java.io.InputStreamReader
	import java.net.URL

	class TwitterCommunicator extends AsyncTask<String, Void, String> {

	AsyncDelegate delegate

	override protected doInBackground(String... params) {
	new URL('https://api.twitter.com/1/friendships/exists.json?screen_name_a='
	+ params.get(0) + '&screen_name_b=' + params.get(1))
	.openConnection.inputStream.readStream
	}

	override onPostExecute(String result) {
	if (delegate != null) {
	delegate.showResult(result)
	}
	}

	def setDelegate(AsyncDelegate delegate) {
	this.delegate = delegate
	}

	def isNetworkAvailable(Context it) {
	val networkInfo = (getSystemService(Context::CONNECTIVITY_SERVICE)
	as ConnectivityManager).activeNetworkInfo
	return networkInfo != null && networkInfo.connected
	}

	def private readStream(InputStream in) {
	return CharStreams::toString(new InputStreamReader(in))
	}
	}
	</pre>


	<li><p>
	To avoid tight coupling between the activity and the
	communicator, we will make use of the delegate pattern. Create
	a new Xtend interface
	<code>AsyncDelegate</code>
	. The interface declares only one method
	<code>showResult(Object)</code>
	. We will call this method from the post execute callback of
	<code>TwitterCommunicator</code>
	.

	<pre class="prettyprint lang-xtend">
	package de.nataliaossipova.isfollowing

	interface AsyncDelegate {
	def void showResult(Object it)
	}
	</pre></li></ul>
	<p>The <code>MainActivity</code> already implements the <code>AsyncDelegate</code>
	interface.
	</p>
	<h3>Build And Run</h3>
	<p>
	Now, when we are done with writing source code, add
	permissions
	<code>android.permission.INTERNET</code>
	and
	<code>android.permission.ACCESS_NETWORK_STATE</code>
	to the Android manifest and let's build an APK and run it on
	an AVD.
	</p>
	<p>
	We need to tell ADT how to export the Xtend libraries. Choose
	<i>Properties -> Java Build Path</i> from the project context
	menu and go to the <i>Order and Export</i> tab. Select the
	checkbox beside <i>Xtend library</i>.
	</p> <img
	src="/community/eclipse_newsletter/2013/march/images/android_screenshot4.jpg"
	alt="New Android project" />
	<p>After closing the Properties window, you can launch the
	application on an existing AVD or a device.</p>
	<h3>Where To Go From Here</h3>

	<p>Now that you know how to use Xtend for Android development,
	go and create awesome Android apps in this sophisticated
	programming language!</p>

	<p>Don't hesitate to let me know if anything of the above is
	confusing to you or if you'd like me to go into more detail.</p>
	<script
	src="http://www.eclipse.org/xtend/google-code-prettify/prettify.js"
	type="text/javascript"></script> <script
	src="http://www.eclipse.org/xtend/google-code-prettify/lang-xtend.js"
	type="text/javascript"></script> <script
	type="text/javascript">
	prettyPrint();
	</script>


	<div class="bottomitem">
	<h3>About the Authors</h3>

	<div class="row">
	<div class="col-sm-12">
	<div class="row">
	<div class="col-sm-8">
	<img class="author-picture"
	src="/community/eclipse_newsletter/2013/march/images/natalia_ossipova1.jpg"
	alt="Natalia Ossipova" />
	</div>
	<div class="col-sm-16">
	<p class="author-name">
	Natalia Ossipova <br /> <a
	href="http://nataliaossipova.wordpress.com/">Freelance
	Software Architect</a>
	</p>
	<ul class="author-link">
	<li><a href="http://nataliaossipova.wordpress.com/">Blog</a></li>
	<li><a href="https://twitter.com/nossipova">Twitter</a></li>
	<li><a href="http://www.linkedin.com/in/nataliaossipova">LinkedIn</a></li>
	<li><a href="<?php echo $original_url; ?>">Original Article</a></li>
	</ul>
	</div>
	</div>
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	</div>
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