It is usually desired that tooltips be shown where extra information has to be displayed on mouse over. The problem here is to generate tooltips for List & ComboBox items.
Lets start with List
List has a showDatatips property that can be set to show the dataTips. You will then have to write a function to return the required string as the dataTip and assign it to the dataTipFunction property of the List…
With ComboBox, its a bit more complicated. The dropDown in a ComboBox, is by default a List, so if we can access the List and then set the above properties, we are done. For this you need to set a dropDownFactory for the ComboBox and then assign the factory object with the above properties that we discussed above for list. Here’s how
First define
private var myDropdownFactory:ClassFactory;
Call initApp() method on creationComplete
private function initApp():void{
myDropdownFactory = new ClassFactory(List);
myDropdownFactory.properties = {showDataTips:true, dataTipFunction:myDataTipFunction}
}Then set this onto the ComboBox
<mx:ComboBox id=”myCB” dataProvider=”{myDP}” labelField=”name” dropdownFactory=”{myDropdownFactory}”/>
And the myDataTipFunction() looks something like this
private function myDataTipFunction(value:Object):String{
return (value.name+”‘s blog is “+value.blog);
}
It looks something like this 
See the application and get the source code on the links below…
I initially thought this should be possible by setting the showDatatips and the dataTipField on the List, but it didn’t work as expected for me. I have logged a bug in the public bugbase…
Posted by raghunt 
