More control over updating UITableView and UITableViewCell - cocoa-touch

Question

I am trying to implement expanding UITableViewCells where I have complete control over the animation of the transition from collapsed to expanded and back.
I have an array, cellDataList, that holds the state of my UITableViewCells, i.e. height, color, data, isExpanded etc.
I implement:
- (CGFloat) tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
if (indexPath == selectedIndex)
return expandedHeight;
return collapsedHeight;
}
and I implement:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
/*
some logic that tests if the indexPath is already selected,
which will collapse the cell, if a previous cell needs to be collapsed before the
new expands etc.
*/
[tableView beginUpdates];
[tableView reloadRowsAtIndexPaths:paths withRowAnimation:UITableViewRowAnimationNone];
[tableView endUpdates];
}
My cell is a custom UITableViewCell where I build my content in drawRect:
The cell has a UIView (background) that serves as a custom background for the cell, this view I would like to
animate from collapsed to expanded and back, not just setFrame in one 'jump', as it does now.
I can't really figure out where to 'intercept' the tableView updater chain, to achieve this.
When I do the [tableView beginUpdates] - [tableView endUpdates] above, it starts to get a bit obscure what happens.
I assume
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
is called to update the cells
at the indexes specified. This in turn will ask heightForCellAtIndexPath which height to set the cell. If I set a breakpoint in my custom cells setFrame: method
I can see the caller is
[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] ().
This sets the new frame for the cell, then I assume [cell setNeedsDisplay] is called somehow so the cell can render for the frame provided.
The [cell setNeedsDisplay] will eventually call my custom drawRect: and render the content of the cell. This works as expected, but I can't figure
out where and how I will animate the frame for my background, also in a way so it is only done when clicked and not every time setFrame: is called (during scrolling etc).
When I do the above the tableView animates to make room for the new cell size, it is
this animation I would like to 'mimic' with the background view on my cell.
I see this effect in apps like Tweetbot and path but I can't seem to replicate it.
Hope some one can help me in the right direction, thanks:)

Answer 1

I am not totally sure that i understood your question exactly:) But you can use Key Value Observer (KVO) to check when you need to play your animation then call your table reload method.
- (void)reloadTable
{
if (self.isViewLoaded) {
[self.tableView reloadData];
}
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
[self reloadTable];
}

Answer 2

The best way to do this is to add a dummy cell below the cell that was tapped. I explain this thorougly here.
Basically:
Keep track of what cells are been tapped in your didSelectRowAtIndexPath and update it appropriately. Which one needs to be deleted? Where will the new dummy cell be next?
Return the correct account whenever the dummy cell is present.
Account for the fact that the dummy cell is not part of your model. Offset the indexPath.