I found that to make it work right I had to do “callLater(scrollToBottom)” whenever the collection changes or the control is resized.

Also, I added a feature: if the user scrolls up from the bottom I don’t want it to scroll back to the bottom when items are added, as is common in chat logs like this.

private var lastChatMaxScroll:Number;

// add as List.resize handler and List.dataProvider COLLECTION_CHANGE handler
private function resetScroller(event:CollectionEvent):void {
if (chatList.scroller.verticalScrollBar.value + 5 >= lastChatMaxScroll) {
callLater(scrollToBottom());
}
else {
lastChatMaxScroll = chatList.scroller.verticalScrollBar.maximum;
}
}

private function scrollToBottom():void { // slightly modified
var delta:Number = 0;
var count:int = 0;
while (count++ < 10){
chatList.validateNow();
delta = chatList.layout.getVerticalScrollPositionDelta(NavigationUnit.END);
chatList.layout.verticalScrollPosition += delta;
lastChatMaxScroll = chatList.scroller.verticalScrollBar.maximum; // new!
if (delta == 0)
break;
}
}