Refresh tileList on DataChange

I happened to come across an issue with tileLists that use a custom itemRenderer.

The problem is that when I change the data provider, the items in the tileList do not redraw appropriately.

After some time spent in digging into this, I found out that for some reason the dataChange event in the itemrenderer is not triggered automatically when the data provider changes.

Note:DataChange event is triggered internally for dataGrids which are bound to a dataProvider, so we wont even notice it,but that is not the case for a tileList.

The event is triggered only when we call tileList.invalidateList().

So here is what I did. Call tileList.invalidateList() every time I change the dataProvider and handle the dataChange event in the itemRenderer and reset the UIControl's properties whatever it may be.

Here is what the view does.

<?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;

[Bindable]
private var dataP:ArrayCollection = new ArrayCollection(
[{isMarried:true, isAnimal:true,name:"Montgomery"},
{isMarried:false, isAnimal:true,name:"Juneau"},
{isMarried:true, isAnimal:false,name:"Little Rock"},
{isMarried:true,isAnimal:true,name:"Ricky Martin"}]);

private function changeFirstElement():void {
dataP.getItemAt(0).name = "changed";
tileList.invalidateList();
}

]]>
</mx:Script>

<mx:TileList itemRenderer="testItemRenderer" dataProvider="{dataP}"
id="tileList"/>
<mx:Button label="change first element" click="changeFirstElement();"/>
</mx:Application>


And here is what the itemRenderere does.

<?xml version="1.0" encoding="utf-8"?>
<mx:Canvas xmlns:mx="http://www.adobe.com/2006/mxml" dataChange="handleDataChange()"
creationComplete="handleCreationComplete()">
<mx:Script>
<![CDATA[
[Bindable]
private var theName:String=new String();

private function handleCreationComplete():void {
if (data != null && data.hasOwnProperty("name")) {
theName =data.name;
}
}
private function handleDataChange():void {
if (data != null && data.hasOwnProperty("name")) {
if (theLabel) {
theName = data.name;
}
}
}
]]>
</mx:Script>
<mx:Label text="{theName}" id="theLabel"/>
</mx:Canvas>


Hope it helps!

Reuse ItemRenderers for Multiple columns

When dealing with item renderers, one will come across all sorts of problems thrown at . One such case is "how to reuse the same itemrenderer"

Picture this case. You have a custom itemrenderer,( imagine a check box within a canvas for now) that performs a specific task and you want to reuse it on multiple columns. But how will the itemrenderer know which field in the arrayCollection is to be used to render itself appropriately?

Alright. Here is the trick.

There is this interface called IDropInListItemRenderer which your itemrenderer will have to implement to get access to listData which can be typeCasted to DataGridListData. The listData variable will hold reference to the owner of the itemRenderer and the hierarchy upwards. Following is the list of steps one has to follow.

1.Create the itemRenderer class that implements the IDropInListItemRenderer.

2.Create an instance variable to buffer the listData , namely _listData.

3.Override the set/get methods of the listData instance variable . In the setter, buffer the listData onto the instance variable

Ex:


private var _listData:DataGridListData;
public function set listData(value:BaseListData):void
{
_listData = DataGridListData(value);
}


Note:The importance of this step is that the itemrenderer can use the _listData variable to find out the name of the dataField , using something like _listData.dataField. Once the name of the dataField is acquire, the value for that datfield can be acquired by using data[_listData.dataField]

4.Override the updateDisplyList() method to update the status of the checkBox based on the value of the dataField.

Ex:

override protected function updateDisplayList(unscaledWidth:Number,unscaledHeight:Number):void {

super.updateDisplayList(unscaledWidth,unscaledHeight);
_instanceCheckBox.selected = Boolean(data[_listData.dataField]);
}

5. Create the datagrid and use the above created item renderer.
Ex:

<mx:DataGridColumn dataField="isMarried" itemRenderer="sampleItemRenderer"/>
<mx:DataGridColumn dataField="isAnimal" itemRenderer="sampleItemRenderer" />




Following is the complete code.

The view:

// View
<?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;
[Bindable]
private var dataP:ArrayCollection = new ArrayCollection(
[{isMarried:true, isAnimal:true,name:"Montgomery"},
{isMarried:false, isAnimal:true,name:"Juneau"},
{isMarried:true, isAnimal:false,name:"Little Rock"},
{isMarried:true,isAnimal:true,name:"Ricky Martin"}]);
]]>
</mx:Script>



<mx:DataGrid dataProvider="{dataP}">
<mx:columns>
<mx:DataGridColumn dataField="isMarried" itemRenderer="sampleItemRenderer"/>
<mx:DataGridColumn dataField="isAnimal" itemRenderer="sampleItemRenderer" />
<mx:DataGridColumn dataField="name"/>
</mx:columns>
</mx:DataGrid>
</mx:Application>



The itemRenderer


package
{
import mx.containers.Canvas;
import mx.controls.CheckBox;
import mx.controls.dataGridClasses.DataGridListData;
import mx.controls.listClasses.BaseListData;
import mx.controls.listClasses.IDropInListItemRenderer;

public class sampleItemRenderer extends Canvas implements IDropInListItemRenderer
{
private var _listData:DataGridListData;
private var _instanceCheckBox:CheckBox = new CheckBox();
private var _currentDataFieldName:String = new String();
public function sampleItemRenderer()
{
super();
}

public function get listData():BaseListData
{
return _listData;
}

public function set listData(value:BaseListData):void
{
_listData = DataGridListData(value);
}
override protected function createChildren():void {
super.createChildren();
addChild(_instanceCheckBox);

}
override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void {
super.updateDisplayList(unscaledWidth,unscaledHeight);
_instanceCheckBox.selected = Boolean(data[_listData.dataField]);
}
}
}

Hope it helps!


Filterfunctions .

Here is a quick little post on how to use filter functions .

The primary use of filterfunctions as it implies is to filter data on a data structure such as ArrayCollection which will in turn filter the data displayed on UI controls like datagrid,combobox.

The filterfunction is called with each item in the arrayCollection as a paramter. Say you have n items in the arrayCollection, the filter function will be called n times with items 0...n passed in as a parameter. The items for which the call returns true are added to the visible list, while the rest are ignored.

Lets jump in to the sample code.

<?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;
[Bindable]
private var dataP:ArrayCollection = new ArrayCollection(
[{type:"1", data:"Montgomery",label:"Montgomery"},
{type:"2", data:"Juneau",label:"Juneau"},
{type:"1", data:"Little Rock",label:"Little Rock"},
{type:"2",data:"test 2",label:"test 2"}]);

private function handleOptionSelect() :void {
if (selectionCombo.selectedItem.toString() == "ALL") {
dataP.filterFunction = null;
} else {
dataP.filterFunction = filterOnTypes;
}
dataP.refresh();
}

private function filterOnTypes(item:Object):Boolean {
if (item.hasOwnProperty("type")) {
if (item.type == selectionCombo.selectedItem.toString()) {
return true;
}
}
return false;
}


]]>
</mx:Script>

<mx:ComboBox change="handleOptionSelect()" id="selectionCombo">
<mx:dataProvider>
<mx:ArrayCollection>
<mx:Object>ALL</mx:Object>
<mx:Object>1</mx:Object>
<mx:Object>2</mx:Object>
</mx:ArrayCollection>
</mx:dataProvider>
</mx:ComboBox>

<mx:DataGrid dataProvider="{dataP}">
<mx:columns>
<mx:DataGridColumn dataField="type"/>
<mx:DataGridColumn dataField="data"/>
</mx:columns>
</mx:DataGrid>
</mx:Application>



Note that the elements in the arrayCollection that do not match the filter criteria removed from the arrayCollection. You can restore the original data set by setting the filter function to null and calling the refresh method again.

Wondering how the AVM knows the original set? it just stores the original data set in the "source" attribute of the arrayCollection.

Hope it helps!


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Complex editors on a datagrid

There are times when you want to have a data grid whose cells can have other complex controls like combobox , numeric stepper.To achieve this multi-entity ,entry form t, we use the inline itemEditor field of the datagrid component.

The key here is the itemEditor property of the datagrid column to which you can specify a class ,aka editor or renderer(either flex built in or custom). Now how will flex know which property of the editor or renderer is the user input? . The “editorDataField” property specifies which property of the renderer is to be taken as the user input. Example: value property of a numeric stepper, when numeric stepper is the itemEditor.

One very important thing to notice here is that the dataprovider is also synched with the values committed on the item renderers.

Here is an example that shows how to do this.

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

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical">

<mx:Script>

<![CDATA[

private function showArrayCollection():void {

resultText.htmlText="";

for (var i:Number=0;i<stateArray.length;i++) {

resultText.htmlText+="Name:"+stateArray.getItemAt(i).name;

resultText.htmlText+=" Age:"+stateArray.getItemAt(i).age;

resultText.htmlText+="<br>";

}

}

]]>

</mx:Script>

<!--

The data provider for the datagrid.The age property will be synched with the user's input,

when he selects it from the age property.

!-->

<mx:ArrayCollection id="stateArray">

<mx:Object name="Amitha" age="25"/>

<mx:Object name="Priyanka" age="27"/>

<mx:Object name="Krups" age="45"/>

</mx:ArrayCollection>

<mx:DataGrid x="531" y="82" editable="true" dataProvider="{stateArray}">

<mx:columns>

<mx:DataGridColumn headerText="Name" dataField="name" editable="false"/>

<mx:DataGridColumn headerText="Age" dataField="age" editable="true"

itemEditor="mx.controls.NumericStepper" editorDataField="value"/>

</mx:columns>

</mx:DataGrid>

<mx:Button label="show" click="showArrayCollection()">

</mx:Button>

<mx:TextArea width="300" height="300" id="resultText">

</mx:TextArea>

</mx:Application>


Hope it helps!!

Events for DUMMIES

Accept it, we all have used events but never really got to know what goes behind the scenes.

So here in vivid little words, I try to throw some light on this.

Here goes my “EVENTS for DUMMIES!”

Flash Player 9 implements an event model based on the World Wide Web Consortium’s (W3C) specification entitled Document Object Model Events available at http://www.w3.org/TR/DOM-Level-3-Events/events.html. According to this document, the lifecycle of an event that deals with display objects consists of three phases: capture, target, and bubbling.

You have probably heard of these names but never got to know why three phases are used??

The reason is simple.W3C recommends so! J

• Capture: During this phase, Flash Player makes a first pass to check every object from the root of the display list to the target component to see if any parent component might be interested in processing this event. By default, events are ignored by the parents of the target component at the capture phase. Its like collecting who and all are interested in the a components events.

Ex:

If component 1 has a code like component2.addEventListener(“eventname”,myfunction);

Component 1 will be added to a list in this phase.

• Target: At this phase, event object properties are set for the target and all registered event listeners for this target will get this event.

Event.name and event.whatever is set now!

• Bubbling: Finally, the event flows back from the target component all the way up to the root to notify all interested parties identified during the capture phase. Not all events have a bubbling phase and you should consult the AS3 language reference for the events you’re interested in.

The three event phases described above don’t apply to the user-defined events because Flash Player 9 doesn’t know about parent-child relations between user-defined event objects. But AS3 developers can create custom event dispatchers, if they want to arrange event processing in three phases.

Hope it helps!

Case insensitive SortCompare Function for Strings

Here is a quick post on how to use the sortCompare function to sort strings.

Here goes the sample.Assuming your dataField is called status.This sortcomparefunction will function insensitive to the case of the strings.

private function statusSortCompareFunction(obj1:Object,obj2:Object):int {

if (!obj1.hasOwnProperty("status")) {

obj1.status = null;

}

if (!obj2.hasOwnProperty("status")) {

obj2. status = null;

}

return ObjectUtil.stringCompare(obj1.status,obj2.status,true);

}

Hope it helps!

Integrating Spring with Flex on TOMCAT

This is a sequel to my post on getting up and running with blazeds/flex/tomcat on eclipse. This little post is going to explain how to integrate your ultra cool flex front end with the spring framework.Checkout http://www.springframework.org/ if you are not familiar with spring or Dependency injection.

Alright.Here are the steps.

1.Setup your blazeds server and client as mentioned in the previous blog post
2.Download the spring framework from http://www.springframework.org. Extract and move the neccessary jars into WEB-INF/lib folder of your server application.
3. Add the spring context param and listener to your web.xml file:

<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml</param-value>
</context-param>

<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

4.Download the flex spring factory from www.adobe.com. COmpile it and have the class file inside your WEB-INF/classes folder .

5. Add the following configuration to your WEB-INF/flex/services-config.xml file:

<factories>
<factory id="spring" class="flex.samples.factories.SpringFactory" />
</factories>

6.Define your components in spring's XML file. Given the above spring
configuration, they would be placed in WEB-INF/applicationContext.xml. This
file can contain components which are intended to be exposed to flex clients as
remote objects as well as classes to be used as Flex Data Management Services
(FDMS) assembler implementations using the Java adapter.

7.To be constructed by Spring, your component should have a zero argument constructor so
Spring can construct an instance. Your applicationContext.xml file might look like:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">

<beans>
<bean name="weatherBean" class="dev.weather.WeatherService" singleton="true"/>

<bean name="myAssembler" class="dev.assemblers.MyAssembler" singleton="true"/>
</beans>

8.Add your flex destination configuration for the components you want to expose to
flex clients. Since these components use the spring factory we define, we add the
additional tag <factory>spring</factory> and the <source> attribute is used to refer
to the spring component's bean name, not the class name as with the default factory.

For Remote object destinations you place your destinations inside of the
<service> tag which refers to the flex.messaging.services.RemotingService,
(by convention this may be in WEB-INF/flex/remoting-config.xml). For example, your
remote destination configuration might look like:

<destination id="WeatherService">
<properties>
<factory>spring</factory>
<source>weatherBean</source>
</properties>
</destination>

9.Use a simple client and set your remote object destination to the one you created on your remoting-config.xml

10.Restart your server.Test. Off you go!!