animating UITableViewHeader to grow/shrink - ios

Question

Im very new to iOS and am trying to figure out how I can animate the tableView header to appear like its sliding down from the top of the view, stay there for 3 seconds, then slide back up and disappear.
I havent done any animation of any kind before so I could really use some help. I dont know where to start. Ive looked at other answers on here but cant seem to figure out how to do it.
ive got my table view appearing just fine with this code in my viewDidLoad of my UITableViewController class
self.headerView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320,15)];
self.headerLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 320, 15)];
self.headerLabel.textAlignment = NSTextAlignmentCenter;
self.headerLabel.text = #"some text";
[self.headerView addSubview:self.headerLabel];
self.tableView.tableHeaderView = self.headerView;
self.tableView.tableHeaderView.frame = CGRectMake(0, 0, 320, 15);
I assume I need to animate the height of my frame.
edit: I found this code which seems like it should work, however it crashes my app when the animation runs
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
[UIView animateWithDuration:3.0f
delay:0.0f
options: UIViewAnimationOptionBeginFromCurrentState
animations:^{
self.headerView.frame = CGRectMake(0.0f, 0.0f, 320.f, 0.0f);
}
completion:^(BOOL finished) {
[self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];
}];
}

Answer 1

I don't know if you can animate a table view's header view like you want to. With a complex UI object like a Table view Apple tends to treat the views that make up the object as private, and bad things tend to happen when you try to manipulate the view hierarch.
If you're not using auto-layout and you want to animate another view that is part of YOUR view hierarchy then your code might be as simple as something like this:
CGPoint center = myView.center;
CGFloat myViewBottom = myView.frame.origin.y + myView.frame.origin.size.height;
//Move the view above the top of it's superview before starting the animation.
center.y -= myViewBottom;
//Animate the view down into position
[UIView animateWithDuration: .2
animations:
^{
myView.center += myViewBottom;
};
completion:
^{
//As the completion block for the first animation, trigger another
//animation to animate the view away again. This time delay
//for 3 second before the 2nd animation.
[UIView animateWithDuration: .2
delay: 3.0
options: 0
animations:
^{
myView.center -= myViewBottom;
};
completion: nil
}
];

Answer 2

Try to use beginUpdates and endUpdates, here is an example:
in your header
#property NSInteger newOffset;
implementation:
- (void) colapseHeader
{
_newOffset = 50;
[self.tableView beginUpdates];
[self.tableView endUpdates];
}
- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section
{
return 50 + _newOffset;
}
- (void) viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
_newOffset = 100;
[self.tableView beginUpdates];
[self.tableView endUpdates];
[self performSelector:#selector(colapseHeader) withObject:nil afterDelay:3];
}