Center row of Buttons in UIScrollView - objective-c

Question

I am adding buttons in a UIScrollView dynamically, but some views only have two buttons and some have 10. I want to center the buttons in the scroll view so It doesn't look like I built them from the left to right. I've tried several tricks from SO and nothing seems to work. setting the content offset was my first approach, but doesn't have the effect I want.
Here is the code I am using:
- (void)addButton:(UIButton *)button {
CGFloat contentWidth = 0.0f;
CGRect buttonFrame = button.frame;
if ([_scrollView.subviews count] == 0) {
buttonFrame.origin.x = self.contentIndicatorWidth + kButtonSeperator;
contentWidth = self.contentIndicatorWidth + buttonFrame.size.width + self.contentIndicatorWidth;
} else {
contentWidth = _scrollView.contentSize.width;
UIButton *lastButton = [_scrollView.subviews lastObject];
buttonFrame.origin.x = lastButton.frame.origin.x + lastButton.frame.size.width + kButtonSeperator;
contentWidth += buttonFrame.size.width + kButtonSeperator;
}
button.frame = buttonFrame;
[_scrollView addSubview:button];
_scrollView.contentSize = CGSizeMake(contentWidth *kContentMultiplicityFactor, _scrollView.frame.size.height);
[_buttons setValue:button forKey:button.titleLabel.text];
totalWidth = contentWidth;
// [_scrollView scrollRectToVisible:[self getButtonAtIndex:0].frame animated:YES];
}

Answer 1

After you add the buttons call this method:
- (void)centerButtons:(NSArray*)buttons {
CGSize scrollViewSize = _scrollView.bounds.size;
// Measure the total width taken by the buttons
CGFloat width = 0;
for (UIButton* b in buttons)
width += b.bounds.size.width + kButtonSeparator;
if (width > kButtonSeparator)
width -= kButtonSeparator;
// If the buttons width is shorter than the visible bounds, adjust origin
CGFloat origin = 0;
if (width < scrollViewSize.width)
origin = (scrollViewSize.width - width) / 2.f;
// Place buttons
CGFloat x = origin;
CGFloat y = 0;
for (UIButton* b in buttons) {
b.center = CGPointMake(x + b.bounds.size.width/2.f, y + b.bounds.size.height/2.f);
x += b.bounds.size.width + kButtonSeparator;
}
_scrollView.contentSize = CGSizeMake(MAX(scrollViewSize.width, width), scrollViewSize.height);
}

Answer 2

In the end, this isn't a very hard problem. I guess you add these buttons on the fly.
You have a scrollview called ScrollView and you have already put in content size.
So you have 10 buttons of different widths :
int btnCount = 10;
int totalWidth = 0;
int spacing = 5;
NSMUtableArray *buttons = [[NSMutableArray alloc] init];
for (int i=0; i<btnCount-1; i++) {
UIButton *b = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[b setTitle:#"some title" forState:UIControlStateNormal];
[b sizeToFit];
CGRect frame = b.frame;
totalWidth += b.frame.size.width;
[buttons addObject:b];
}
totalWidth += (btnCount * spacing);
UIView *btnView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, totalWidth, 40)];
int priorButtonX = 0;
for (UIButton *b in buttons) {
CGRect frame = b.frame;
frame.origin.x = priorButtonX;
b.frame = frame;
priorButtonX = frame.origin.x + spacing;
[btnView addSubview:b];
}
int scrollSizeWidth = scrollView.contentSize.width;
int placeX = (scrollSizeWidth /2) - (btnView.frame.size.width /2)
CGRect btnViewFrame = btnView.frame;
btnViewFrame.origin.x = placeX;
bbtnView.frame = btnViewFrame;
[scrollView addSubView:btnView];
You might want to do something with Y placement, but that one is very simple. This code can be written in fewer lines, and use fewer variables, but this is done to make it easier to read.