A user recently asked why the call to DataProvider.getItemIndex() in the following example returns -1:

import fl.controls.List;
import fl.data.DataProvider;

var dp:DataProvider = new DataProvider();
dp.addItem({label:"AL", data:"Montgomery"});
dp.addItem({label:"AK", data:"Juneau"});
dp.addItem({label:"AR", data:"Little Rock"});
// assign the data provider to the list
var myList:List = new List();
myList.dataProvider = dp;
myList.rowHeight = 35;
myList.rowCount = dp.length;
myList.move(10, 10);
addChild(myList);	// display the list
// this attempt to locate an item in the list returns -1
trace("Index is: " + myList.dataProvider.getItemIndex({label:"AK", data:"Juneau"}));

Paul Robertson explains:

The problem is that the getItemIndex() method matches exact object references, not objects with matching properties. The first object, {label:”AK”, data”Juneau”}, may
have identical property values with the one that’s being passed to the getItemIndex() method, but they’re not exactly the same object – they’re just two different objects that happen to have the same property values.

To get a match with getItemIndex(), you need to pass a reference to the actual object that’s in the data provider. To do that, of course, you need a reference to the
same object, for example in a variable. Here’s a variation of your code that works:

import fl.controls.List;
import fl.data.DataProvider;

var dp:DataProvider = new DataProvider();
var item1:Object = {label:"AL", data:"Montgomery"};
var item2:Object = {label:"AK", data:"Juneau"};
var item3:Object = {label:"AR", data:"Little Rock"};
dp.addItem(item1);
dp.addItem(item2);
dp.addItem(item3);

var myList:List = new List();
myList.dataProvider = dp;
myList.rowHeight = 35;
myList.rowCount = dp.length;
myList.move(10, 10);
addChild(myList);

trace("Index is: " + myList.dataProvider.getItemIndex(item2));

Of course, you are probably really trying to do some sort of search to find the index of an item that matches a user entered string. The only way I can see to do that is to loop over the data provider one item at a time and compare the property values. You can either loop over the data provider directly using dp.length and
dp.getItemAt(index), or else keep the objects in a separate array. This code demonstrates the first approach:

import fl.controls.List;
import fl.controls.Button;
import fl.controls.TextInput;
import fl.data.DataProvider;

var dp:DataProvider = new DataProvider();
dp.addItem({label:"AL", data:"Montgomery"});
dp.addItem({label:"AK", data:"Juneau"});
dp.addItem({label:"AR", data:"Little Rock"});

var myList:List = new List();
myList.dataProvider = dp;
myList.rowHeight = 35;
myList.rowCount = dp.length;
myList.move(10, 35);
addChild(myList);

var ti:TextInput = new TextInput();
ti.width = 100;
ti.move(10, 10);
addChild(ti);

var btn:Button = new Button();
btn.width = 50;
btn.label = "Search";
btn.move(120, 10);
addChild(btn);
btn.addEventListener(MouseEvent.CLICK, btn_click);

function btn_click(event:Event):void
{
for (var i:int = 0, len:int = dp.length; i < len; i++)
{
if (dp.getItemAt(i).data == ti.text)
{
trace("Index is: " + i.toString());
return;
}
}
trace("Item not found");
}