Iphone Dev - Drop down list of Buttons when button pressed

I need to implement a button (let's say with a picture of arrow down before pressed), that when pressed, will open a drop down list other button I'll set dynamically. The drop needs to show one button at a time, using some kind of animation.

Is there a preferred way of doing it. (ne开发者_运维技巧ver worked with animation before) Similar source code would be of great help.

Thanks

I did something similar where I had a table view with a navigation bar. The bar had a button to show/hide filters, which would animate down from the top. The code I used was:

  CGFloat filterViewHeight = kExtendedFilterViewHeight;
  if(![self includeSecondaryFilter])
   filterViewHeight = kDefaultFilterViewHeight;

  if(!allButton.selected && [self includeSecondaryFilter])
   filterViewHeight -= kSecondaryFilterHeight;

  filtersView.frame = CGRectMake(0.0, -filterViewHeight, 320.0, filterViewHeight);
  [self.view addSubview:filtersView];

  CGRect tableViewFrame = itemTableView.frame;
  CGRect filtersViewFrame = filtersView.frame;

  [UIView beginAnimations:nil context:NULL];
  [UIView setAnimationDuration:0.3];
  [UIView setAnimationDelegate:self];

  tableViewFrame.origin.y = filterViewHeight;
  tableViewFrame.size.height -= filterViewHeight;
  itemTableView.frame = tableViewFrame;

  filtersViewFrame.origin.y = 0.0;
  filtersView.frame = filtersViewFrame;

  [UIView commitAnimations];

Hope this helps!