Your data provider will be some sort of collection view, but I don't know what kind of collection view you are using. What you want to do is to add items to the data provider... Your code above should give you an error, I believe, because addAllAt() returns void (that is undefined / nothing), it modifies collection in place. I would imagine this will work:
var dp:ICollectionView = dg.dataProvider as ListCollectionView; if (dp) dp.addAllAt(figure.getListDataAtt(), dp.length - 1); else dg.dataProvider = figure.getListDataAtt();