iOS 8 - Initially hide a UITableView's headerView from view - ios

Question

Just like in the native iOS Mail app, when I push a UITableViewController onto a UINavigationController, I would like to make it so that the UITableView initially appears slightly scrolled downwards, obscuring its headerView beneath the navigation controller's navigation bar.
At the same time, even if the height of all of the cells is smaller than the height of the table view, it should be possible for the user to scroll up and down to explicitly show or hide the header view again.
With that logic, it would appear that there are two considerations to make for this implementation:
1) Ensuring that the minimum content size of the table view is at least the height of the table view's frame + the height of the header view.
2) When the table view is initially presented, the content offset is incremented by the height of the header view.
I've tried manually setting both the contentOffset and contentSize properties of the table view in 'viewWillAppear', however this appears to have no effect (It's possible the table view is getting reloaded after that point). Trying to set them in 'viewDidAppear' will work, but that's too late as it only gets called once the 'push' animation has completed.
While this sort of question has been asked before for previous iOS versions, I was unable to get any of them working in iOS 8. Additionally, they all dealt with changing the offset, but not the contentSize of the table view.
Has anyone gotten this sort of behavior working in iOS 7 and/or 8 before?

Answer 1

Update - (30/1/2015)
Alright. This wasn't sitting well with me last night, so I had another play with it, and I found a MUCH better and cleaner solution.
I discovered that the tableView property of UITableViewController is NOT readonly. So it actually makes more sense to simply manage the contentSize property in a UITableView subclass and then assign that subclass back to the UITableViewController.
#implementation TOCustomTableView
- (void)setContentSize:(CGSize)contentSize
{
CGFloat scrollInset = self.contentInset.top + self.contentInset.bottom;
CGFloat height = (CGRectGetHeight(self.bounds) - scrollInset) + CGRectGetHeight(self.tableHeaderView.frame);
contentSize.height = MAX(height, contentSize.height);
[super setContentSize:contentSize];
}
#end
---
#implementation TOCustomTableViewController
- (void)viewDidLoad
{
[super viewDidLoad];
self.tableView = [[TOCustomTableView alloc] initWithFrame:self.view.bounds style:UITableViewStylePlain];
}
#end
This way, the table view's minimum contentSize is always explicitly set to be the height of the table view + the headerView size, achieving the desired effect with zero jittering. :)
Original Answer
trick14 pointed me in the right direction. So the correctly functioning code I ended up with.
- (void)resetTableViewInitialOffset
{
CGPoint contentOffset = self.tableView.contentOffset;
contentOffset.y = self.tableView.contentInset.top + CGRectGetHeight(self.headerView.frame);
self.tableView.contentOffset = contentOffset;
}
- (void)resetTableViewContentSize
{
CGSize contentSize = self.tableView.contentSize;
CGFloat scrollInset = self.tableView.contentInset.top + self.tableView.contentInset.bottom;
CGFloat height = (CGRectGetHeight(self.view.bounds) - scrollInset) + CGRectGetHeight(self.headerView.frame);
contentSize.height = MAX(height, contentSize.height);
self.tableView.contentSize = contentSize;
}
- (void)viewDidLayoutSubviews
{
[super viewDidLayoutSubviews];
if (!self.headerBarInitiallyHidden) {
[self resetTableViewContentSize];
[self resetTableViewInitialOffset];
self.headerBarInitiallyHidden = YES;
}
}
I'm also making sure to call 'resetTableViewContentSize' each time I perform a 'reloadData' on the table view as well.