FileReference events not firing?

If the UPLOAD_COMPLETE_DATA event (or any other FileUpload related event) isn't fired after a succesful upload then you need to check whether your page returns something. It's enough that it just returns for example 'OK' but it at least has to return something.

Certified Adobe Flex Developer

I've waited and waited but it seems that the Adobe Flex 3 certification exam won't come before the release of Adobe Flex 4... Therefore I finally decided to do the Adobe Flex 2 certification and guess what: I passed :) It was a nice bunch of questions, some on UI, some on application design (even some UML) and some on data services. Most of them were 'practical' question but of course some are less 'obvious'.

Where to put your removeEventListeners?

Everyone tells you to make sure to execute a removeEventListener for each addEventListener but where do you put this code? Most people put their addEventListeners in the creationComplete event but there's no destructionComplete event...

There are 2 options:

• Or you don't use removeEventListener and make sure that you use a weak reference when doing addEventListener (setting the 5th parameter of addEventListener to true)
  
• Or you attach event listeners in the "addedToStage" event and you remove them again in the "removedFromStage" event

Why Adobe didn't set the 'weak reference' parameter by default to 'true' is unclear to me. The current situation is probably one of the major causes of memory leaks in Flex applications...

Degrafa component not showing up?

There seems to be some problem when building a Degrafa component in MXML. It seems that using "Surface" as the outer container results in an invisible component. The workaround is simple: put a Canvas around it but don't ask me why :)

Dynamic (Advanced)DataGrid columns

Trying to add columns dynamically to your DataGrid or AdvancedDataGrid and having trouble with specifically setting the width of a column?

Try the following:

var cols: Array = datagrid.columns;
cols.push(newColumn);
datagrid.columns = cols;
// The following line is very important
// (otherwise the grid won't be aware of the new columns yet)
datagrid.validateNow();
// Force the width of a specific column
cols[0].width = 40;

Reducing the space between the legend marker and the legend label

If you ever try to reduce the space between the legend markers and the legend labels:

LegendItem
{
horizontalGap: 0;
verticalGap: 0;
}

Deep object compare

Ever wanted to check in Flex whether all the public members of an object are the same? You can use the ObjectToString method in that case:

public class SerializeUtil
{
public static function ObjectToString(object: *): String
{
var ba: ByteArray = new ByteArray();
ba.writeObject(object);
return ba.toString();
}
public static function ObjectToByteArray(object: *): ByteArray
{
var ba: ByteArray = new ByteArray();
ba.writeObject(object);
ba.position = 0;
return ba;
}
}

To do the actual comparison:

if (SerializeUtil.ObjectToString(object1)==SerializeUtil.ObjectToString(object2))
{
// Objects are 'equal'
}
else
{
// Objects are not 'equal'
}