Items in Tree control move around when data is submitted using custom ItemRenderer

Question

I'm working on a Tree control with an XMLListCollection as
its dataProvider.
The dataProvider has information looking like this :
quote:
<?xml version='1.0' encoding='utf-8'?>
<INFO>
<FIELD label="STR_USER_NAME"
type="text"
value=""
>
</FIELD>
<FIELD label="STR_USER_EMAIL"
type="text"
value=""
>
</FIELD>
<FIELD label="STR_OPTIONAL"
type="branch"
value="0"
>
<FIELD label="STR_USER_ADDRESS"
type="text"
value=""
>
</FIELD>
<FIELD label="STR_USER_POSTAL_CODE"
type="text"
value=""
>
</FIELD>
</FIELD>
</INFO>
So in the Tree control I'd like the information to show up
with a label and
an
editable textbox for each item :
[Label] [textbox]
To do this I made a tree like this :
quote:
<mx:Tree id="userTree"
editable="true"
rendererIsEditor="true"
editorDataField="curVal"
itemRenderer="{new ClassFactory(ItemRendererUser)}"
itemEditEnd="e_ProcessData(event);"
dataDescriptor="{new DataDescriptorUsers()}"
showRoot="false"
verticalScrollPolicy="{ScrollPolicy.AUTO}"
/>
where the e_ProcessData() function looks like this (I used
http://livedocs.adobe.com/flex/201/html/wwhelp/wwhimpl/js/html/wwhelp.htm?href=c
elleditor_073_16.html#202105 as a guide) :
quote:
public function e_ProcessData(event:ListEvent):void
event.preventDefault();
userTree.editedItemRenderer.data.@value =
ItemRendererUsers(event.currentTarget.itemEditorInstance).curVal;
userTree.destroyItemEditor();
userTree.dataProvider.notifyItemUpdate(userTree.editedItemRenderer);
} // END OF e_ProcessData()
I attached the rest of the files because they're a little
bit longer.
When I run the program, the data shows up fine when it is
initialized the
very
first time, and I made a test button that just dumps the
contents of the
dataProvider in a trace statement to verify that the data has
been set
properly.
The problem I've run into is whenever the textfield is
edited, the item
that
I've selected jumps around the list.
For example, if I edit the item "STR_USER_NAME" after I
finish the edit, it
will move from the very first position in the Tree to the
bottom of the
Tree.
I traced the contents of the dataProvider and the
dataProvider structure
stays
the same, with the "STR_USER_NAME" at the top, but if I look
at the flex app
in
the web browser, its position is at the bottom of the Tree.
This happens for every other item I try to edit... I read in
the
documentation
that the ItemRenderers are recycled, so it means I should be
checking to
make
sure the initial states are covered, but I'm not sure how
this affects my
application.
Can anyone help me out with this ? Its very confusing - I've
tried making
an
ItemRenderer using pure actionscript, mxml and the
combination you see in
this
example and I always end up with the same behaviour - So I
must be missing
something critical...
// ItemRendererUsers.mxml
<?xml version="1.0" encoding="utf-8"?>
<mx:Canvas xmlns:mx="
http://www.adobe.com/2006/mxml"
verticalScrollPolicy="{ScrollPolicy.OFF}"
horizontalScrollPolicy="{ScrollPolicy.OFF}"
creationComplete="initItemRendererUsers();"
>
From my FAQ:
Q: I've created a custom itemRenderer component to use in a
List
based component (Datagrid, TileList, HorizontalList, etc.).
When my List
first displays, everything looks fine, but when I scroll it
or change the
dataProvider, some of the itemRenderers show values or
formatting that
aren't right. How do I fix this?
A: List-based components don't draw a renderer for every item
in the
dataProvider. Instead, they create enough to display what is
on screen now,
plus one or two more waiting in the wings. This means they
recycle the
renderers rather than creating new ones when you change
dataProvider or
scroll up and down. When you use a creationComplete event to
set up the
itemRenderer, that event doesn't happen again when the
renderer is used for
a different set of data. The solution to this is to override
the set data
protected function that most components have.
For more information, check out the following resources:
http://www.adobe.com/devnet/flex/articles/itemrenderers_pt1.html?devcon=f1
http://blogs.adobe.com/aharui/2007/03/thinking_about_item_renderers_1.html
Please note, I post this FAQ weekly, and you can find a
permanent copy of it
here
http://www.magnoliamultimedia.com/flex_examples/Amys_Flex_FAQ.pdf

Answer 1

"peterh8234" <[email protected]> wrote in
message
news:gaqttd$kft$[email protected]..
> Yes - the set and get functions are listed down below.
But the quirky
> behaviour
> is the same regardless of whether I override the set and
get functions or
> not.
>
> I noticed there was another variable called listData -
should I be using
> that
> one or the data variable to read and write to the
dataProvider ?
>
> // _data
> [Bindable] public var _data:Object;
> [Bindable("dataChange")]
> //
> override public function get data():Object
> {
> trace('[ItemRendererDefault.GET data()] called for {' +
> _data.attribute("label") + '}.');
> return _data;
> } // END OF get data()
>
> //
> override public function set data(value:Object):void
> {
> _data.@value = inputText.text;
> trace('[ItemRendererDefault.SET data()] called for {' +
> _data.attribute("label") + '}.');
>
> invalidateProperties();
> } // END OF set data()
Your set data needs to set a flag that gets picked up in
commitProperties()
and does your thing that you were doing before in
creationComplete. You
should see examples of this in the links I posted. Instead of
this:
_data.@value = inputText.text;
you should look at implementing IDropInListItemRenderer,
which will allow
you to dynamically determine which field to look at, instead
of hardcoding
it. You also might wind up overwriting the stored value with
a null value
when the List passes the stored value in. I'd encourage you
to really go
through those links I posted and make sure you understand
what they're
saying. The itemRenderer life cycle is one of the hardest
things to
understand, but once you understand it, it makes many things
in Flex much
easier. It's worth investing the time.