Some days ago I was working on a project, in which I have to make a scroll component for device because I have to show a very long list on device. First I used simple touch list, which I had used in my earlier projects for desktop and for devices for short list comparatively. When I checked that component on iPhone 4, it completely stuck for only 500 list renderers. It was like a shock or me because I have to load around 2500 list, and it was sticking in 500.
Then I use flex’s recycle list component, which is perfect for my need, but the another problem for me is that I couldn’t use flex component as my project was a pure ActionScript project.
Then I decided to reform that touch list component with pooling concept, so that I can recycle the renderers and can load it for large list. I used the flex recycle concept and apply it in my touch list component. I used object pooling for recycling, which works on following concept:
The List creates an instance of a class called ObjectPool, which manages used and unused renderers. Whenever the List needs a new renderer, it asks the pool for a new one and when it does not need a renderer, it returns it to the pool. The pool tries to find unused renderers to satisfy the request for a new renderer and if it cannot, will create a new object and return that.
The core part of the logic resides in the onVerticalScroll function. The list always maintains a map of all visible renderers and as the scrollbar scrolls, the map is recalculated and renderers managed if the map is changed.
You can find the source code here:
Hacks 