Get frame from certain UISegmentedControl index? - ios

Question

In my app, I use a UIPopoverController and I use the presentPopoverFromRect API. What I am doing now is just setting it to the frame of my whole UISegmentedControl. However I want to be more precise than this. Is there any way to get the frame of a specific index in the UISegmentedControl?
Thanks!

Answer 1

For our project we needed the actual frames of each segment, frame division wasn't enough. Here's a function I wrote that calculates the exact frame for every segment. Be aware that it accesses the segmented control actual subviews, so it might break in any iOS update.
- (CGRect)segmentFrameForIndex:(NSInteger)index inSegmentedControl:(UISegmentedControl *)control
{
// WARNING: This function gets frame from UISegment objects, undocumented subviews of UISegmentedControl.
// May break in iOS updates.
NSMutableArray *segments = [NSMutableArray arrayWithCapacity:self.numberOfSegments];
for (UIView *view in control.subviews) {
if ([NSStringFromClass([view class]) isEqualToString:#"UISegment"]) {
[segments addObject:view];
}
}
NSArray *sorted = [segments sortedArrayUsingComparator:^NSComparisonResult(UIView *a, UIView *b) {
if (a.frame.origin.x < b.frame.origin.x) {
return NSOrderedAscending;
} else if (a.frame.origin.x > b.frame.origin.x) {
return NSOrderedDescending;
}
return NSOrderedSame;
}];
return [[sorted objectAtIndex:index] frame];
}

Answer 2

If the segments are equal, why not just divide the width of the control by the number of the selected segment (+1 because numbering starts at 0)?
EDIT: Like this
-(void)showPopover:(id)sender {
if ((UISegmentedControl*)sender.selectedSegmentIndex == 0)
[self.popover presentPopoverFromRect:CGRectMake(self.segmentedControl.frame.size.width/6, self.segmentedControl.frame.origin.y, aWidth, aHeight)]
}
It's over 6 (I'm assuming a 3 segment implementation), because you have to get the center of the segment, and 3 would put it on the lines. And if you do some simple math here (let's assume the whole control is 60 px wide), then 60/3 yeilds 20. Because each segment is 20 px wide, the width of 60 over six yields the correct answer 10.

Answer 3

This can be done much easier without matching class names, providing that you use no custom segmented control (Swift version)
extension NSSegmentedControl {
func frameForSegment(segment: Int) -> NSRect {
var left : CGFloat = 0
for i in 0..<segmentCount {
let w = widthForSegment(i)
if i == segment {
let off = CGFloat(i) + 2 // Account for separators and border.
return NSRect(x: left + off, y: bounds.minY, width: w, height: bounds.height)
}
left += w
}
return NSZeroRect
}
}

Answer 4

If somebody is searching for a solution for NSSegmentedControl, I've slightly modified #erik-aigner's answer. For UISegmentedControl it should work similarly.
This version improves the geometry computation for spacing and the code in general. Disclaimer: It was tested only for a segmented control placed in a toolbar.
import AppKit
public extension NSSegmentedControl {
/// The width of a single horizontal border.
public static let horizontalBorderWidth: CGFloat = 3
/// The height of a single vertical border.
public static let verticalBorderWidth: CGFloat = 2
/// The horizontal spacing between segments.
public static let horizontalSegmentSpacing: CGFloat = 1
/// Returns the frame of the specified segment.
///
/// - Parameter segment: The index of the segment whose frame should be computed.
/// - Returns: The frame of the segment or `.zero` if an invalid segment index is passed in.
public func frame(forSegment segment: Int) -> NSRect {
let y = bounds.minY - NSSegmentedControl.verticalBorderWidth
let height = bounds.height
var left = NSSegmentedControl.horizontalBorderWidth
for index in 0..<segmentCount {
let width = self.width(forSegment: index)
if index == segment {
return NSRect(x: left, y: y, width: width, height: height)
}
left += NSSegmentedControl.horizontalSegmentSpacing
left += width
}
return .zero
}
}

Answer 5

Swift 5.3 version of #CodaFi's answer:
func showPopover(_ sender: Any?) {
if sender?.selectedSegmentIndex as? UISegmentedControl == 0 {
popover.presentPopover(fromRect: CGRect(x: segmentedControl.frame.size.width / 6, y: segmentedControl.frame.origin.y, width: aWidth, height: aHeight))
}
}

Answer 6

For me widthForSegment returns 0, so the other answers always fail to produce frame. I think a better solution is to just get the frame of a subview:
public extension UISegmentedControl {
func frame(forSegment segment: Int) -> CGRect {
subviews[segment].frame
}
}