David,
In IB, I have a vertical UIStackView with an image view and a text view
(stacked in that order). I add the activity indicator programmatically:
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
// add activity indicator and start animation
if _useActivityIndicator == true {
// set constraints
_imageView.addSubview(_activityIndicator)
_activityIndicator.centerXAnchor.constraintEqualToAnchor(_imageView.centerXAnchor).active
= true
_activityIndicator.centerYAnchor.constraintEqualToAnchor(_imageView.centerYAnchor).active
= true
_activityIndicator.startAnimating()
}
}
I get this error:
2015-10-26 22:44:42.971 Historic Sites Navigator[247:13410] Unable to
simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't
want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't
understand, refer to the documentation for the UIView property
translatesAutoresizingMaskIntoConstraints)
(
"<NSAutoresizingMaskLayoutConstraint:0x14dbda90 h=--& v=--&
UIActivityIndicatorView:0x14eb3760.midX == + 10>",
"<NSLayoutConstraint:0x14dce780 H:|-(0)-[UINavigationBar:0x14dd17d0]
(Names: '|':UIView:0x14d88e30 )>",
"<NSLayoutConstraint:0x14d7a200 H:[UINavigationBar:0x14dd17d0]-(0)-|
(Names: '|':UIView:0x14d88e30 )>",
"<NSLayoutConstraint:0x14d7f660 UIStackView:0x14dbcf50.trailing ==
UINavigationBar:0x14dd17d0.trailing>",
"<NSLayoutConstraint:0x14d81a70 UIStackView:0x14dbcf50.leading ==
UINavigationBar:0x14dd17d0.leading>",
"<NSLayoutConstraint:0x14dca540 UIActivityIndicatorView:0x14eb3760.centerX
== UIImageView:0x14dd16c0.centerX>",
"<NSLayoutConstraint:0x14ea41c0 'UISV-canvas-connection'
UIStackView:0x14dbcf50.leading == UIImageView:0x14dd16c0.leading>",
"<NSLayoutConstraint:0x14e75910 'UISV-canvas-connection'
H:[UIImageView:0x14dd16c0]-(0)-| (Names: '|':UIStackView:0x14dbcf50 )>",
"<NSLayoutConstraint:0x14e746c0 'UIView-Encapsulated-Layout-Width'
H:[UIView:0x14d88e30(320)]>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x14dca540 UIActivityIndicatorView:0x14eb3760.centerX ==
UIImageView:0x14dd16c0.centerX>
Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch
this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed
in <UIKit/UIView.h> may also be helpful.
I do not understand how the error is occurring.
On Oct 26, 2015, at 2:02 PM, David Duncan
<[email protected]<mailto:[email protected]>> wrote:
On Oct 25, 2015, at 12:13 PM, Peters, Brandon
<[email protected]<mailto:[email protected]>> wrote:
David,
I tried your suggestion, but the program terminates. I get this in the console:
view did load...
2015-10-25 15:10:57.893 Historic Sites Navigator[766:538109] *** Terminating
app due to uncaught exception 'NSGenericException', reason: 'Unable to activate
constraint with items <UIActivityIndicatorView: 0x145933b0; frame = (0 0; 20
20); hidden = YES; layer = <CALayer: 0x14593220>> and <UIImageView: 0x145966c0;
frame = (0 0; 320 208); autoresize = RM+BM; userInteractionEnabled = NO; layer
= <CALayer: 0x145967a0>> because they have no common ancestor. Does the
constraint reference items in different view hierarchies? That's illegal.’
You need to ensure they have a hierarchy relationship before activating the
constraints – you probably didn’t add one as a subview of the other yet.
*** First throw call stack:
(0x2635c68b 0x37716e17 0x2635c5d1 0x271fa7cd 0xce7d8 0xceeb4 0x2a43821b
0x2a43879f 0x2a755c47 0x2a86185d 0x2a7590b1 0x2a547cff 0x2a547b39 0x2a5476ad
0x2a54724f 0x2a459535 0x2a45942f 0x29cf45a9 0x123ed73 0x1243815 0x2631f9ad
0x2631dea7 0x26271249 0x26271035 0x2f354ad1 0x2a486899 0xc5a44 0x37e62873)
libc++abi.dylib: terminating with uncaught exception of type NSException
I will continue to work on it though. Thanks...
On Oct 25, 2015, at 1:11 PM, David Duncan
<[email protected]<mailto:[email protected]>> wrote:
On Oct 24, 2015, at 8:45 PM, Peters, Brandon <[email protected]> wrote:
Devs,
I have a UIStackView, which holds an image view and a text view. The image view
has an activity indicator view as a subview (I add this programmatically). When
the view initially view loads, I center the activity indicator view within the
image view and starting the animation for the AIV. But, in the process of
waiting for the image to load, if I rotate the image view, the AIV needs to be
re-centered. I added code to listen for the status bar orientation change
notification, and have a method to invoke upon the notification
(UIApplicationDidChangeStatusBarOrientationNotification). In that method, I
attempt to get the bounds of the image view and use that to re-center the AIV
within the image view. But, it seems that the value of the bounds of the image
view is not changing when the device orientation changes. Is there a “reliable"
way to get the updated bounds for a view after the device orientation has
changed? Code ->
Why do all this at all? Just add 2 constraints that tie the center of the
activity indicator to its superview and it will remain centered always.
[_activityIndicator.centerXAnchor
constraintEqualToAnchor:_imageView.centerXAnchor].active = YES;
[_activityIndicator.centerYAnchor
constraintEqualToAnchor:_imageView.centerYAnchor].active = YES;
(or equivalent if you need to support prior to iOS 9).
// start listening for orientation changes
NSNotificationCenter.defaultCenter().addObserver(self, selector:
"orientationDidChange:",
name: UIApplicationDidChangeStatusBarOrientationNotification,
object: nil)
…
func orientationDidChange(notification: NSNotification) {
// get image view bounds
let viewBounds = _imageView.bounds
// recenter the activity indicator
_activityIndicator.center = CGPointMake(CGRectGetMidX(viewBounds),
CGRectGetMidY(viewBounds))
}
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