Justifying UIVIews on the iPhone: Algorithm Help
- by coneybeare
I have been messing around with a way to justify align a collection of UIView subclasses within a containing view. I am having a little bit of trouble with the algorithm and was hoping someone could help spot my errors. Here is pseudocode of where I am now:
// 1 see how many items there are
int count = [items count];
// 2 figure out how much white space is left in the containing view
float whitespace = [containingView width] - [items totalWidth];
// 3 Figure out the extra left margin to be applied to items[1] through items[count-1]
float margin = whitespace/(count-1);
// 4 Figure out the size of every subcontainer if it was evenly split
float subcontainerWidth = [containingView width]/count;
// 5 Apply the margin, starting at the second item
for (int i = 1; i < [items count]; i++) {
UIView *item = [items objectAtIndex:i];
[item setLeftMargin:(margin + i*subcontainerWidth)];
}
The items do not appear to be evenly spaced here. Not even close. Where am I going wrong?
Here is a shot of this algorithm in action:
EDIT: The code above is pseudocode. I added the actual code here but it might not make sense if you are not familiar with the three20 project.
@implementation TTTabStrip (JustifiedBarCategory)
- (CGSize)layoutTabs {
CGSize size = [super layoutTabs];
CGPoint contentOffset = _scrollView.contentOffset;
_scrollView.frame = self.bounds;
_scrollView.contentSize = CGSizeMake(size.width + kTabMargin, self.height);
CGFloat contentWidth = size.width + kTabMargin;
if (contentWidth < _scrollView.size.width) {
// do the justify logic
// see how many items there are
int count = [_tabViews count];
// 2 figure out how much white space is left
float whitespace = _scrollView.size.width - contentWidth;
// 3 increase the margin on those items somehow to reflect. it should be (whitespace) / count-1
float margin = whitespace/(count-1);
// 4 figure out starting point
float itemWidth = (_scrollView.size.width-kTabMargin)/count;
// apply the margin
for (int i = 1; i < [_tabViews count]; i++) {
TTTab *tab = [_tabViews objectAtIndex:i];
[tab setLeft:(margin + i*itemWidth)];
}
} else {
// do the normal, scrollbar logic
_scrollView.contentOffset = contentOffset;
}
return size;
}
@end
