59

I am developing using iOS 6 auto layout

I would like to log a message displaying the frame width of the view.

I can see the textView on the screen.

But I get the width and height as zero, am I missing something ?

NSLog(@"textView    = %p", self.textView);
NSLog(@"height      = %f", self.textView.frame.size.height);
NSLog(@"width       = %f", self.textView.frame.size.width);

textView    = 0x882de00
height      = 0.000000
width       = 0.000000
user1046037
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9 Answers9

156

Actually, above answers are not quite right. I followed them and got zeros again and again.

The trick is to place your frame-dependent code to the viewDidLayoutSubviews method, which

Notifies the view controller that its view just laid out its subviews.

Do not forget that this method is called multiple times and is not the part of ViewController's life cycle, so be careful while using this.

Hope it will be helpful to someone.

Just wanted to add, that for my program without landscape mode NOT using Auto Layout is way much simplier... I tried, though =D

dreamzor
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    From experience, this is the earliest callback after autolayout does its work. I recommend using, for example, a BOOL to catch the first time this is called and do frame dependent logic. It's not very elegant but gets the job done until there's proper callbacks for specific autolayout constraints. – ArkReversed Jul 16 '13 at 11:50
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    @dreamzor, how do I know if it is the last viewDidLayoutSubviews? I found on iOS 7, only one viewDidLayoutSubviews will be called before viewDidAppear, but on iOS 8, I see mutiple viewDidLayoutSubviews before viewDidAppear. This is annoying, because the first viewDidLayoutSubviews will give wrong frame size on iOS 8, so I have to ignore it for first time – Wingzero Apr 02 '15 at 11:07
  • @Wingzero In my project the fifth time is correct, so how can I ignore others? – Elijah_Lam Jun 07 '15 at 14:42
  • @Elijah_Lam I think you can't. it is totally a system behaviour, and you have no control. As long as iOS think the view needs layout, it will trigger it – Wingzero Jun 08 '15 at 01:48
  • @Wingzero What's your solution at last? – Elijah_Lam Jun 08 '15 at 01:55
  • it is work around I guess. I have to put some code that needs frame information to viewDidAppear, or in viewDidLayoutSubViews, I just accept whatever the frame is, though it is a waste. – Wingzero Jun 08 '15 at 02:05
  • It should probably be noted that if you use `[viewDidLayoutSubviews]` to (synchronously) refresh a view, the effects will be visible in a subsequent from-view-controller-Foo-to-view-controller-Bar transition animation, if any. If you wait until `[viewDidAppear:]` with a refresh, it will be "surprise" rendered already post- view controller transition animation. – Gary Jul 26 '16 at 12:42
  • Add `if yourView.bounds != .zero` If your view's bounds is still `nil` when using `viewDidLayoutSubviews`. Your view might not be the first that is laid out. – Anro Swart Jul 03 '19 at 19:43
59

I think auto layout hasn't had the time to layout your views by the time you call this. Auto layout hasn't happened by the time viewDidLoad is called, because it's called just after the views are loaded and it's only after that that the views are placed into the view controller's view hierarchy and eventually laid out (in the view's layoutSubviews method).

Edit: this answer points out why the scenario in the question doesn't work. @dreamzor's answer points out where to place your code in order to solve it.

Community
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Jesper
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  • I tried to log the message in `viewDidLoad`. Which method gets invoked after the auto layout has been completed. The reason I ask is because I want to calculate the width before the user can interact with the textView. So logging the object description might not help bcuz I want to use the width for some other calculation. – user1046037 Sep 21 '12 at 09:03
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    No, `viewDidLoad` happens before auto layout. Auto layout happens lazily after a view has been added to another view (which is shortly after `viewWillAppear` has been called, but probably not reliably before `viewDidAppear`). The only reliable way to know is to know when `layoutSubviews` is finished on the view controller's view. – Jesper Sep 21 '12 at 09:24
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    Why are you trying to get the frame anyway? If you want to do calculations based on it and do layout yourself, you will probably end up battling auto layout. – Jesper Sep 21 '12 at 09:25
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    I was trying to calculate the number of letters that can fit into the UITextView to clip it and give it a "..." kind of look. – user1046037 Sep 21 '12 at 09:31
  • Since you can't do that while someone's entering text, use a `UILabel` with `lineBreakMode` to one of the `NSLineBreakByTruncating...` values and set your constraints so that the label is always the same width, height and position as the text view. – Jesper Sep 21 '12 at 12:12
  • Thanks Jasper, but the only problem with using a UILabel is that when there is a only a single line of text in the UILabel, the text gets displayed at the vertical centre (height / 2) instead of the top of the label. – user1046037 Sep 21 '12 at 17:30
  • Really appreciate your help on this. For completeness, pls can you update your answer to include the "reason the frame width is zero is bcuz viewDidLoad happens before auto layout". So that I can mark it as answered. – user1046037 Sep 21 '12 at 17:33
  • Edited to fit what the problem was and good luck on solving your problem. – Jesper Sep 25 '12 at 07:30
  • Jesper, thanks a lot for your pointers, `viewDidAppear` seems to happen after auto layout. If there is a better approach let me know. – user1046037 Sep 28 '12 at 02:56
35

Include in your viewDidLoad()

self.view.setNeedsLayout()
self.view.layoutIfNeeded()

Before accessing yourview.frame.size.width

diegosantiviago
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31

Solution

  • Place that code in viewDidAppear

Reason

  • viewDidLoad happens before autolayout is completed. So the position is not yet set by autolayout that was specified in xib
  • viewDidAppear happens after autolayout is completed.
user1046037
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    I placed the code in viewDidAppear and yet still, my view's frame NSLog shows zeros. – dreamzor Jan 03 '13 at 19:43
  • Actually viewDidAppear is called before viewDidLayoutSubviews as for iOS 6.0 so dreamzor is right. – vedrano Feb 21 '13 at 09:16
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    In iOS 6, based on my testing, I used navigation controller in the 2nd controller, the `viewDidLayoutSubviews` was called before `viewDidAppear` but in `viewDidLayoutSubviews` the subview's frame width remains to be zero. Only in `viewDidAppear`, the subview's frame width seems to have the correct value. – user1046037 Feb 21 '13 at 13:03
13

Actually I managed to force the layout update before my code within the viewDidLoad:

override func viewDidLoad() {
        super.viewDidLoad()

        println("bounds before \(self.previewContainer.bounds)");
        //on iPhone 6 plus -> prints bounds before (0.0,0.0,320.0,320.0)

        self.view.setNeedsLayout()
        self.view.layoutIfNeeded()

        println("bounds after \(self.previewContainer.bounds)");
        //on iPhone 6 plus -> prints bounds after (0.0,0.0,414.0,414.0)

        //Size dependent code works here
        self.create()
    }

UPDATE: This doesn't seem to work anymore

Francescu
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10

This is really strange feature. But I found:

If you want to get frame without using layoutsubviews method, Use this one:

dispatch_async(dispatch_get_main_queue(), ^{
        NSLog(@"View frame: %@", NSStringFromCGRect(view.frame));
    });

This is really strange!!!

SamSol
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7

None of the above answers worked completely for me, except viewDidLoad but that has the side effect of not displaying what I want until after the view has animated in, which looks poor.

viewDidLayoutSubviews should be the correct place to run code that relies on the autolayout being complete, but as others have pointed out it is called multiple times in recent iOS versions and you can't know which is the final call.

So I resolved this with a small hack. In my storyboard, mySubview should be smaller than its containing self.view. But when viewDidLayoutSubviews is first called, mySubview still has a width of 600, whereas self.view seems to be set correctly (this is an iPhone project). So all I have to do is monitor subsequent calls and check the relative widths. Once mySubview is smaller than self.view I can be sure it has been laid out correctly.

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()

    if self.mySubview.bounds.size.width < self.view.bounds.size.width {

        // mySubview's width became less than the view's width, so it is
        // safe to assume it is now laid out correctly...

    }
}

This has the advantage of not relying on hard-coded numbers, so it can work on all iPhone form factors, for example. Of course it may not be a panacea in all cases or on all devices, but there are probably many ingenious ways to do similar checks of relative sizes.

And no, we shouldn't have to do this, but until Apple gives us some more reliable callbacks, we're all stuck with it.

Echelon
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3

You can only find out the size after the first layout pass. Or Just call below method then after you got actual width of you view.

[yourView layoutIfNeeded];
Bhavesh Patel
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0

I agree with the solution of "user1046037"

If you are using both atuoLayout guides, and code at the same time, you would better to put frame(or NSlayoutConstraints) programming into "ViewDidAppear", especially when you are designing UI for multiple devices.

Based on my tests, iOS14 will take autoLayouts from screen(default iPhone 11 Pro Max) before "ViewDidLoad", and update it in "ViewDidAppear".

For people who are not familiar with view cycle, its "load view from storyboard" -> "ViewDidLoad" -> "ViewWillAppear" -> "ViewDidAppear".