All posts by ssh

Binding warnings when using Object in a List dataProvider

If you have built a custom item renderer for a DataGroup or List you may have come across warnings in your Flash Builder console output similar to this:

warning: unable to bind to property 'firstName' on class 'Object' (class is not an IEventDispatcher)

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Changing the position of the scroll bars in a spark List

The default spark List skin wraps the the underlying DataGroup with a Scroller component to easily provide scrolling functionality. Custom skinning the Scroller component isn’t very flexible; you can custom skin each scrollbar to change the visuals on them, but you can’t easily reposition them. In these cases it usually makes more sense to get rid of the Scroller and hook up the scrollbars directly.
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Expanding item renderers in a DataGroup or List

The spark DataGroup component is designed to take data items and pass them through an item renderer to create a visual representation of that data. In Flex 4 it is very easy to build custom item renderers.

This sample application demonstrates how you can create an item renderer that only shows some information by default and allows the user to drill down to see more information by clicking on an item or it’s associated “twisty” icon.

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Performance implications of the List itemRenderer vs. itemRendererFunction properties

The spark List component in Flex 4 has virtualization enabled by default. Virtualization is an optimization that only renders items that are currently in view which allows the List to support very large data sets. You can learn more about how virtualization works in Flex 4 by reading the Spark Virtualization Spec.
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Introduction to the DataGroup Component in Flex 4

DataGroup is a new component introduced in Flex 4 that is responsible for turning data items like Strings and Objects into visual elements. The process of turning boring old data items into a visual representation is called item rendering. DataGroup is the lightest weight component that deals with item rendering. It has no skin and no concept of selection. A SkinnableDataContainer is exactly the same as a DataGroup except it has a skin and a List provides selection functionality.
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