Adding Drag and Drag functionality in Adobe Air

In this tutorial I will teach you step by step how to use the out of the box drag & drop functionality provided by flex list controls.

Just some basic theory before we go into code. The drag & drop process has three stages – initiation, dragging and dropping.

The initiation is when the user clicks on a flex component and keeps the button pressed. In this case the component that the user clicks on is the drag initiator. Any flex component that supports dragging will handle either the mouseDown() or mouseMove() event to initiate the drag & drop operation. The event handler will then create a DragSource object which contains data related to the object being dragged. For example if you are dragging a file between two components, the DragSource object will contain a reference to a File object. Once the DragSource is constructed the DragManager.doDrag() method is called where the first argument is a reference to the object that initiated the drag, the second argument is the DragSource object and the third argument is a reference to the mouse event that called the event handler. There is a fourth optional argument that allows to specify a drag proxy that may be used to represent the object being dragged on the screen(e.g. a semi-transparent version of the drag initiator)

In the Dragging stage the user moves the flex component across the screen up to the drop target. If you specify a drag proxy image, that is what is shown on the screen when dragging the component. If not specified a rectangle will be shown instead.

In the dropping stage when the component being dragged arrives to a potential drop target, a dragEnter event is raised. The event handler that handles this event should check whether the DragSource object contains data that is of an acceptable format. If that’s the case then DragManager.acceptDragDrop() is called indicating that the drop target is happy in accepting the dragged data.

In this tutorial I will teach you step by step how to use the out of the box drag & drop functionality provided by flex list controls.

Just some basic theory before we go into code. The drag & drop process has three stages – initiation, dragging and dropping.

The initiation is when the user clicks on a flex component and keeps the button pressed. In this case the component that the user clicks on is the drag initiator. Any flex component that supports dragging will handle either the mouseDown() or mouseMove() event to initiate the drag & drop operation. The event handler will then create a DragSource object which contains data related to the object being dragged. For example if you are dragging a file between two components, the DragSource object will contain a reference to a File object. Once the DragSource is constructed the DragManager.doDrag() method is called where the first argument is a reference to the object that initiated the drag, the second argument is the DragSource object and the third argument is a reference to the mouse event that called the event handler. There is a fourth optional argument that allows to specify a drag proxy that may be used to represent the object being dragged on the screen(e.g. a semi-transparent version of the drag initiator)

In the Dragging stage the user moves the flex component across the screen up to the drop target. If you specify a drag proxy image, that is what is shown on the screen when dragging the component. If not specified a rectangle will be shown instead.

In the dropping stage when the component being dragged arrives to a potential drop target, a dragEnter event is raised. The event handler that handles this event should check whether the DragSource object contains data that is of an acceptable format.  If that’s the case then DragManager.acceptDragDrop() is called indicating that the drop target is happy in accepting the dragged data.

Fortunately for list controls most of this work is already done for you. Implementing drag & drop is very simple:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="horizontal">
     <mx:ArrayCollection id="source">
            <mx:Array>
            <mx:Object singer="Michael Jackson" />
            <mx:Object singer="Jennifer Lopez" />
            <mx:Object singer="Janet Jackson" />
            <mx:Object singer="Paul Mcarthney" />
        </mx:Array>
    </mx:ArrayCollection>

   <mx:ArrayCollection id="destination">
      <mx:Array>
          <mx:Object singer="Sheryl Crowe"/>
      </mx:Array>
   </mx:ArrayCollection>
   <mx:DataGrid dataProvider="{source}" dragEnabled="true" dragMoveEnabled="true"/>
   <mx:DataGrid dataProvider="{destination}" dropEnabled="true"/>
</mx:Application>

In the example above by setting dragEnabled to <b>true</b> allows the rows inside the data grid to be dragged. For any dragged rows to be accepted by the other data grid we need to set dropEnabled to true on that target DataGrid. We also set dragMoveEnabled to true to enable moving rows between data grids.

Ok, now let’s see how we can add drag & drop support to our file system manager. The steps required to do this are:

Step 1

We need to set the dragEnabled and the dropEnabled properties to true on both FileSystemDataGrid. The reason we do on both is because we want to allow the user to copy or move files in both directions: from left to right and right to left.

Step 2

We need to override the default handler for the DragEvent.DRAG_DROP event. This is because the standard drag & drop behavior for the FileSystemDataGrid isn’t quite what we need. In this event handler we need to call event.preventDefault() so that the default event handler is not called. The event handler inspects what file is specified inside the DragSource object carried by the event and performs the copy/move operation as specified by the key that user pressed. If the user just drags a file between the two data grids while pressing the shift key a move file operation is performed. Otherwise the default is to do a copy operation. If the file operation goes is successful we refresh the contents of two FileSystemDataGrid’s, otherwise an alert box is shown.

Here is the code:

 /**
  * Determines what object was dropped in the data grid
  */
 private function handleDragDrop(event:DragEvent):void {
 	// we do this because we want to override the default drag and drop
 	// behaviour implemented in the DataGrid
 	event.preventDefault();
 	var dragSource:DragSource=event.dragSource;
 	if (dragSource.hasFormat("items")) {
 		var items:Array = dragSource.dataForFormat("items") as Array ;
 		for each (var item:File in items) {
 			// copy this file to the directory indicated by fs2
 			// make sure that the origin data grid is not the same as the dest
 			if (event.dragInitiator!= event.target) {
 				var fileDest:File = FileSystemDataGrid(event.target).directory.resolvePath(item.name)

 				var dataGrid:FileSystemDataGrid=event.currentTarget as FileSystemDataGrid;
 				item.addEventListener(Event.COMPLETE, refreshFileSystems);
 				// if the user has pressed the shift key then he just
 				// wants to copy the file
 				if (event.shiftKey)
 				{
 					this.copyFile(item, fileDest);

 				}
 				else {
 					this.moveFile(item, fileDest);
 				}

 			}
 		}
 	}
 }

Click here to download the File System Manager Air app with Drag and Drop support


It is very cool to drag and drop a file from one file system data grid to another. However wouldn’t it be even cooler to be able to drag and drop files from the operating system desktop to Air file manager? That kind of drag & drop requires native drag & drop support. If you are interested in native drag and drop support then read my post on Native Drag and Drop in Adobe Air with example

Integrate Adobe Flex and JBOSS using BlazeDS – Part II

In the first part of this tutorial I showed you an example on how to integrate flex with JBOSS using BlazeDS. In this example we used RemoteObject in Actionscript to create a new instance of uk.co.spltech.remote.RemoteService and call the callMe() method remotely. The method returned a list of strings that we used to populate a datagrid.
In the second part of this tutorial we will do something slightly more useful. This time we will be invoking an EJB 3.0 bean managed by the application server.

Step 1

To be able to invoke EJB 3.0 from flex you need to download and copy FlexEJBFactory.jar to $JBOSS_HOME/server/default/lib. Or you can copy it to a local directory in your project separate from JBOSS e.g. example7/jbosslib and add the following line to $JBOSS_SERVER/server/default/conf/jboss-service.xml:

<classpath codebase="/usr/java/eclipse/workspace/example7/jbosslib" archives="*"/>

Previously all the BlazeDS jars were located in the WAR:WEB-INF/lib directory. But this is not going to work now because we need to see the jars within the context of the entire EAR. For that reason we need to move all those jars to to $JBOSS_SERVER/server/default/lib(or to a local directory inside your project e.g. jbosslib):

flex-ejb-factory.jar
flex-messaging-common.jar
flex-messaging-core.jar
flex-messaging-opt.jar
flex-messaging-proxy.jar
flex-messaging-remoting.jar
backport-util-concurrent.jar

Step 2

Because we will be invoking EJB 3.0 components we need to change the build process so that it creates an EAR file instead of a WAR. We add the following lines to the createjars target:

<jar jarfile="build/example7.jar">
 <fileset dir="${build.classes.dir}">
    <include name="uk/co/spltech/remote/*.class" />
 </fileset>
       
    </jar>

    <zip zipfile="build/example7.ear">
 <zipfileset dir="build">
  <include name="example7.war" />
 </zipfileset>
 <zipfileset dir="${build.dir}/resources" prefix="META-INF">
  <include name="application.xml" />
 </zipfileset>
       <zipfileset dir="build">
  <include name="example7.jar" />
 </zipfileset>
     </zip>

Step 3

Add the new ejb3 factory to flex/services-config.xml:

<factories>
     <factory id="ejb3" class="com.adobe.ac.ejb.EJB3Factory"/>
 </factories>

Step 4

Inside the uk.co.spltech.remote package create the following classes:

package uk.co.spltech.remote;

import java.util.List;

/**
 * This is an example of an interface where you can
 * declare all the methods that you want to call remotely
 * 
 * @author Armindo Cachada
 *
 */
public interface RemoteService {
 /**
  * I am not doing anything useful except to just show that I can be invoked remotely
  * from Adobe Flex using RemoteObject.
  * 
  */
 public List<String> callMe();
}

And the implementation of the interface:

package uk.co.spltech.remote;

import java.util.ArrayList;
import java.util.List;

import javax.ejb.Local;
import javax.ejb.Stateless;

/**
 * This remote service is called using BlazeDS/LiveCycle DS from Flex
 * 
 * @author Armindo Cachada
 *
 */
@Stateless(name = "remoteService")
@Local(RemoteService.class)
public class RemoteServiceImpl implements RemoteService {

 
 /**
  * I am not doing anything useful except to just show that I can be invoked remotely
  * from Adobe Flex using RemoteObject.
  * 
  */
 public List<String> callMe() {
  System.out.println("I was invoked!");
  List<String> result = new ArrayList<String>();
  result.add("Michael Jackson");
  result.add("Beatles");
  result.add("Tina Turner");
  return result;
 
 }
}

Step 5

Add the new destination to flex/remoting-config.xml:

<destination id="remoteService" >
        <properties>
              <factory>ejb3</factory>
              <source>example7/remoteService/local</source>
              <scope>application</scope>
         </properties>
   </destination>

There are two differences in the destination declaration:

  • The factory node indicates that we want to use the EJB3Factory declared in services-config.xml
  • The source instead of referencing a class name is changed to reference an EJB3 bean via JNDI.

Step 6

We are going to use the same mxml code as the one for Part I of this tutorial but we need to change the flex compiler settings:

-services "/usr/java/eclipse/workspace/example7/resources/flex/services-config.xml" -context-root "/example7" -locale en_US

After you have followed all these steps you should be good to go!




Download source code for JBOSS+Adobe Flex+BlazeDS project Part II

To save bandwidth I didn’t include all the jars needed:

flex-ejb-factory.jar
flex-messaging-common.jar
flex-messaging-core.jar
flex-messaging-opt.jar
flex-messaging-proxy.jar
flex-messaging-remoting.jar
backport-util-concurrent.jar

Copy these jars to the jbosslib directory inside the project. Don’t forget to change jboss-service.xml to reference this directory. Otherwise nothing will work.

Good luck!

Integrate Adobe Flex and JBOSS using BlazeDS – Part I

In this tutorial I will give you step by step instructions on how to integrate Adobe Flex and JBOSS using BlazeDS.
Although in this tutorial I am addressing BlazeDS, the steps in this tutorial should also apply to Adobe Flex LiveCycle Data Services. The only difference are the jars that you copy to your WEB-INF/lib directory. For those who want to integrate BlazeDS with Struts 2, the instructions in this tutorial should also be helpful.

In the Java Backend:

Step 1

Download blazeds.war from http://opensource.adobe.com/wiki/display/blazeds/Downloads

Step 2

Unzip blazeds.war. Copy the files in WEB-INF/lib and WEB-INF/flex to your web project under the same path in your web app.

Step 3

Edit web.xml and add the following lines:

    <!-- Http Flex Session attribute and binding listener support -->
    <listener>
        <listener-class>flex.messaging.HttpFlexSession</listener-class>
    </listener>

    <!-- MessageBroker Servlet -->
    <servlet>
        <servlet-name>MessageBrokerServlet</servlet-name>
        <display-name>MessageBrokerServlet</display-name>
        <servlet-class>flex.messaging.MessageBrokerServlet</servlet-class>
        <init-param>
            <param-name>services.configuration.file</param-name>
            <param-value>/WEB-INF/flex/services-config.xml</param-value>
       </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>MessageBrokerServlet</servlet-name>
        <url-pattern>/messagebroker/*</url-pattern>
    </servlet-mapping>

Step 4

Create a simple java class with a simple method that we will invoke from Adobe Flex:

package uk.co.spltech.remote;

import java.util.ArrayList;
import java.util.List;

/**
 * This remote service is called using BlazeDS/LiveCycle DS from Flex
 * 
 * @author Armindo Cachada
 *
 */
public class RemoteService { 
 /**
  * I am not doing anything useful except to just show that I can be invoked remotely
  * from Adobe Flex using RemoteObject.
  * 
  */
 public List<String> callMe() {
  System.out.println("I am being invoked!");
  List<String> result = new ArrayList<String>();
  result.add("Michael Jackson");
  result.add("Beatles");
  result.add("Tina Turner");
  return result;
 }
}

Step 5

Create a new destination in remoting-config.xml:

<destination id="remoteService" >
   <properties>
        <source>uk.co.spltech.remote.RemoteService</source>
        <scope>application</scope>
   </properties>
</destination>

The source of the destination can be a fully qualified class name, a jndi reference or a spring bean. We will discuss that in a later post. For this example we just specify a class name.

The scope of the destination can be one of:

  • application – there is only one instance of the class for the entire application(i.e. global in atg, singleton in spring)
  • session – there is one instance per user session
  • request – for each http request a new instance of the class is created

In Adobe Flex:

Step 1

Create a new project in Adobe Flex. Please make sure that the Application Server type is set to none.
Why? Fair question to ask since most instructions say to do exactly the opposite. I found those instructions not really helpful in the case of JBOSS since they assume I can provide the directory containing the application after it is deployed to JBOSS. That works quite well for tomcat because it simply extracts the war file under webapps. The path is always the same. In the case of JBOSS the path to the application changes after each deployment…

Step 2

The only reason Adobe Flex asks you for the path to the root folder of your web application is so that it can provide two arguments to the flex compiler:

  • services – The path to the Adobe flex data services configuration file
  • context-root – The context root of your web application

After you create your web application add the following arguments to the flex compiler:

-services "/usr/java/eclipse/workspace/example6/resources/flex/services-config.xml" -context-root "/example6"

Step 3

Let’s create a very simple flex application that invokes the callMe() method in uk.co.spltech.remote.RemoteService. This method returns an ArrayList with a list of items:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" >
<mx:Script>
 <![CDATA[
  import mx.collections.ArrayCollection;
  import mx.controls.Alert;
  import mx.rpc.events.ResultEvent;
  import flash.utils.getQualifiedClassName;
  
  
  /**
   * Populates the data list using the results returned by callMe()
   */
  private function populateList(event:ResultEvent):void {
   var result:ArrayCollection= ArrayCollection(event.result);
   singerList.dataProvider= result;
  }
 ]]>
</mx:Script>
 <mx:RemoteObject id="myService" destination="remoteService" result="populateList(event)"/>
 <mx:List id="singerList" >
  
 </mx:List>
 <mx:Button click="myService.callMe();" label="Call Remote Function"  />
</mx:Application>

Step 4

Compile the flex app and copy all the generated swf/html/js to your jboss web app.

Step 5

Deploy the war file to JBOSS and test it under http://localhost:8080/example6

If you click in the “Call Remote Function” button you should see a list of results returned by the method callMe().

Download source code for JBOSS+Adobe Flex+BlazeDS project

Note that, in order to make the zip smaller, I didn’t include the BlazeDS jar files. You need to manually copy them to the lib directory before generating the war file.

Click here to read Part II

Adobe Flex with Struts 2 using HttpService

Using HttpService is the easiest way in which you can integrate Adobe Flex and Struts 2. As an example I will show you how you can create a registration form in Adobe Flex which calls a struts 2 action to create new users. Note that this example is very simple and for demonstration purposes. I am not adding any validation in flex and not even creating the users in a database. All I show you is how you can pass data between flex and struts.

First let me show you the steps you need to perform in Adobe Flex:

Step 1

Create the registration form in mxml:

<mx:Form label="Registration Form">
 <mx:FormHeading label="Registration Form">
 </mx:FormHeading>
 <mx:FormItem label="First Name">
  <mx:TextInput id="firstName">
  </mx:TextInput>
 </mx:FormItem>
 <mx:FormItem label="Last Name">
  <mx:TextInput id="lastName">
  </mx:TextInput>
 </mx:FormItem>
 <mx:FormItem label="Email">
   <mx:TextInput id="email">
  </mx:TextInput>
 </mx:FormItem>
 <mx:FormItem label="Username">
  <mx:TextInput id="username">
  </mx:TextInput>
 </mx:FormItem>
 <mx:FormItem label="Password">
  <mx:TextInput id="password" displayAsPassword="true">
  </mx:TextInput>
 </mx:FormItem>
 <mx:FormItem>
  <mx:Button label="Register" click="registerUser()"/>
 </mx:FormItem>
</mx:Form>

Step 2

Create the HttpService object:

<mx:HTTPService id="registerService" showBusyCursor="true" useProxy="false" url="register.action" resultFormat="e4x" method="POST" result="registerConfirmation(event)" fault="registerFailed(event)"/>
  • register.action is the Struts 2 action that registers the user
  • registerConfirmation(event) is the function that is called if the http service call is successful.
  • registerFailed(event) is the function that is called if an error occurs. For example if the server is down. The event object gives you access to any xml/html that might be returned upon the call of the action.
  • resultFormat specifies in which format you want to view the results. It can be text, xml or an object. There are 5 possible values for this field:
    • object – An XML object is returned and is parsed as a tree of ActionScript objects
    • xml – Returns literal XML in an XMLNode object
    • e4x – Returns literal XML that can be accessed using ECMAScript for XML(E4X) expressions.
    • flashvars – The result is text in flashvars format, value pairs separated by ampersands. Flex returns this result in an actionscript object
    • array – The result is XML that is returned in an Array even if there is only one top level node.

Step 3

Write the actionscript call to submit the form:

public function registerUser():void {
      var params:Object = { 'user.firstName': firstName.text,'user.lastName': lastName.text, 'user.email':email.text, 'user.password':password.text }; 
      this.registerService.send(params);
}

Step 4

Create registerConfirmation(). This method checks whether the registration was successful. We can know that by inspecting the XML that is returned.

private function registerConfirmation(event:ResultEvent):void {
        var xml:XML=XML(event.result); 
 if (xml != null && xml.item == true) {
  mx.controls.Alert.show("Registration Successful!");
 }
 else {
  mx.controls.Alert.show("The registration was not successful.");
 }
 }}

Step 5

If we can’t call the action on the server because of some networking issue we also should give some feedback to the user.

   
/**
 * Display a message to the user explaining what went wrong
 */
private function registerFailed(event:FaultEvent):void {
 mx.controls.Alert.show(event.fault.message);
}

Now let’s create our Struts 2 Action:

Step 1

Create RegisterAction.java

package uk.co.spltech.web.actions;

import uk.co.spltech.beans.User;

import com.opensymphony.xwork2.ActionSupport;

/**
 * Creates a new user
 * 
 * @author Armindo Cachada
 *
 */
public class RegisterAction extends ActionSupport {

 private User user;
 
 private Boolean success;
 
 public Boolean getSuccess() {
  return success;
 }

 public void setSuccess(Boolean success) {
  this.success = success;
 }

 public User getUser() {
  return user;
 }

 public void setUser(User user) {
  this.user = user;
 }

 /**
  * Registers a user
  * 
  * @return
  */
 public String register() {
  System.out.println("Checking user");
  if ( this.getUser()!= null) {
   User u = this.getUser();
   if (u.getEmail()!= null && !u.getEmail().equals("") && u.getPassword()!= null 
     && !u.getPassword().equals("") ) {
    System.out.println("Successfully registered user with email=" + u.getEmail());
    this.success=true;
   }
   else {
    this.success=false;
    System.out.println("Error registering user");
   }
  }
  else {
   this.success=false;
   System.out.println("Error registering user");
  }
  
  return SUCCESS;

 }
 
}

Step 2

Add action name=’register’ to struts.xml

<package name="user" extends="struts-default">
        <action name="register" method="register" class="uk.co.spltech.web.actions.RegisterAction">
           <result type="xslt">   <param name="exposedValue">{success}</param></result>
        </action>
</package>

Source for “Adobe Flex with Struts 2 using HttpService” Example


To compile this example you will need to copy the following libraries to the lib folder:

commons-fileupload-1.2.1.jar
commons-io-1.3.2.jar
commons-logging.jar
freemarker-2.3.13.jar
ognl-2.6.11.jar
struts2-core-2.1.6.jar
xwork-2.1.2.jar
struts2-convention-plugin-2.1.6.jar