Scrollview lag while adding new views on ios

Hello

My view structure is basicly like that

<scrollview> 
    <view>
        <subview>
        </subview>
        ... 18 ..
        <subview>
        </subview>
    </view>
</scrollview>

When user scrolls to bottom, i make a http request and acording to that request i create 20 more subviews and put them into to main view.

This has no lag when i test on android, but on ios, while loading new subviews, it disables scrolling and i need to wait about 3-4 seconds until its enabled to scroll.

Also I dont add this new subviews one by one, i create 20 of them and put them in to another temporary view and i add that temporary view to "view".

I thought this may happen because i add so many views, so i tried to add only 1 view but the result was still same.

Is there a way to do that without lag, i checked twitter, foursquare, pinterest apps, they work smoothly.

Thanx in advance