I'm developing an app targetting iOS6/7, and I've lost two hours staring at a storyboard, trying to understand why autolayout doesn't do what I want it to do.
Basically, I have a scene containing a scroll view and in it, I want to have a UIIMage anchored at the bottom right. Therefore, I set four constraints for the image:
Width equals
Height equals
Bottom space to superview and
Trailing space to superview
XCode does not complain about the positioning, so I run my app with confidence, only to find that it is not shown in any orientation. It's just nowhere to be found!
I know that to find how autolayout implemented the constraints and did its magic, I have to inspect the view.bounds rect. I checked at the viewDidAppear event, to find its value to be as expected though:
Image pos is: 0.000000,0.000000 106.000000x103.000000
The frame is of course at the actual position in the storyboard which I guess is to be expected.
Here is a screen cap of my Storyboard:
Any ideas?
Update:
Some more info:
If I remove all constraints and run the app, the image view is shown at the bottom right of my view in portrait, but when rotating, as expected, it is not shown.
Update 2:
This all should fall in the dreaded UIScrollView and AutoLayout threads. In the end I reverted to using a UIView, inside of which is a UIScrollView containing all the content I wanted to scroll (so that no text fields are hidden by the keyboard in landscape mode). The image I wanted anchored at the bottom was left at the container UIView and it all worked as intended.
If you want to anchor to bottom right, Programmatic autoresizingMask has been far more consistent for me.
It's slightly opposite of IB so if you want to anchor bottom right, you want the left margin flexible and the top margin flexible
yourView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleTopMargin;
This means that bottom margin, right margin, height and width will all remain the same, keeping it in the lower right of your view.
Related
I am making a note taking app in xcode8 for iOS 10.2. The note is consist of a textfield, textview and imageview. I am adding textview and imageview in separate scrollviews (to provide the facility of zooming and adjusting image). Then I have added both scroll views in a stackview to ensure that imageview and textview stands side by side in a landscape mode. To do that, I have added variation to axis property of stackview( width=any, height= compact and Gamut=any, and set that to the horizontal, as shown in right corner of screenshot to see view hierarchy without any constraints).
I have tried many constraints but, every time it fails to adopt. Let's take an example, I am adjusting size of the scrollviews on the size of content(by setting top,bottom,leading and trailing constraint), the stack view is adjusted to the main view. Now, the only thing that needs to be adjusted is text view and imageview with respect of stack view. But, here is the tricky part If I include a fixed trailing constraint of text view to the stack view; it will work in portrait mode.As soon I turn into landscape mode that constraint will not work(the trailing constraint which have 0 distance from stackview) because the edge will be side to the imageview not to the stackview(because I am putting image and text side by side as explained above) which will make textview larger than required, same goes for imageview's leading constraint to the stack view and vertical distance constraint betweem image view and textview.I think the root of the problem is I have made a variation to the axis of a stack view (in order to get text and image side by side in landscape mode) but, that was necessary part.Can anyone have solution for this? Do you think there can be other problem? Should I choose Intrinsic Size of scrollviews to placeholder option or let it be system default?
Thank you.
So I hope I understand the question and I will try to walk you through what I understand you hope to accomplish. I preface this by saying I just started using UIStackView because of backwards compatibility.
Note. To get the magic of ScrollView with AutoLayout I almost always embed them in another UIView. There are reasons to not but in this case you will see how valuable this is to AutoLayout.
Step 1) Drag your UIStackView and add Top,Bottom,Leading, and Trailing. Now add 2 UIViews and set the UIStackView to Fill Equally. It will now look like the image(Background colors to check your work).
Step 2) Now add a UIScrollView to each of these UIViews. Add Leading,Trailing,Top,and Bottom on each of these.
Step 3) Add a UITextView and UIImageView to the ScrollViews respectively. Now Autolayout is mad at us :( but we will fix that.
Step 4) Drag from the UIImageView to the View that is holding the UIScrollView(First Set of Views we added). See image
-Choose the option to add Equal Widths. See Image
Repeat the same step but add Equal Heights. Now add Top, Bottom, Leading, and Trailing to the ScrollView.
Step 5) Repeat exact Step 4 with UITextView
Your final view hierarchy should look like this.
Now you can rotate your UIStackView and do what you want I think.
And Horizontal
Side by Side Preview
I did add a <= 0.1 equal heights multiplier on the textfield at the top but I don't know if that was necessary.
Enjoy.
In an iOS 8 app, I'm trying to create a screen that has a "parallax header", i.e., an image header that grows as you pull down. I would like to do this using only constraints in Interface Builder, if possible.
Here is a nice guide by Pete Hare on how to do such a thing, and I've also had good help at looking at this example project by Bill Carson. However, contrary to these projects, this is not the header to a scrolling area that's taller than the screen, like a Table View; it's just one page. And for some reason, I can't get things to work in my app. I find Scroll Views in Interface Builder rather confusing to begin with. Could anyone walk me through the steps?
Why, certainly! First we'll set up a view controller with a scroll view.
Create an empty View Controller. Give its initial View the Xcode Specific Label Root View so we can tell things apart.
Add a Scroll View. Resize it to fill the view controller, and add constraints for Leading, Trailing, Top and Bottom to equal the superview's corresponding edges. (I do this by control-dragging from Scroll View to View in the Document Outline, hold down the Option and Shift key and then select all four edges, and then Add Constraints.)
Enable Bounce Vertically in the Scroll View's Attribute Inspector.
Add a simple View to the Scroll View and pin its edges to its superview -- the Scroll View -- in the exact same way as we did with the Scroll View to Root View (although this time we don't need to hold Option key when adding constraints). Give the new view the Xcode Specific Label Scrolling Content.
Xcode is not happy, it says Scroll View is missing constraints: "needs constraints for X position or width" and "needs constraints for Y position or height". Let it automatically add missing constraints, it will add constraints for the center of Scrolling Content to the center of Scroll View, in X and Y directions.
By setting a background color to the Scrolling Content, we can now run and confirm that the scroll view with vertical bounce is working as intended. Nice. Now, let's add the header.
Add a nice header image to the project assets, and drag an Image View to the Scrolling Content. Label it Header Image. Select your image asset as the Header Image's image. Drag the corners of the Image View so that it is aligned to the top, left and right edges of your view. Now let's go through the constraints to set on the Image View.
We want the top edge to be fixed to the top of the screen, regardless of how the user is scrolling. So we need it to be pinned to something outside of the Scroll View. You may try fixing it to the Root View's top edge, but unfortunately, that does not work for some reason. What does work is to pin it to the Top Layout Guide. You'll do this easiest by control-dragging in the Document Outline, between the Header Image and the Top Layout Guide and accpet the suggested constant.
The bottom edge of the Header Image needs to be pinned to something inside the Scroll View. Ultimately, we'd like it to be set to a fixed distance from the top of the Scrolling Content -- but Interface Builder won't let us do that. You can only set it to some distance from the bottom of the Scrolling Content, which is not very practical since you will then have to take the height of the device into account. What we instead do is to add another view directly beneath the Header Image, pin that view's top edge to some distance from the Scrolling Content's top edge, and then pin the Header Image's bottom edge to our new view's top edge. This could be a regular View that holds the rest of your user interface below the header. But for this example (and to demonstrate a later point in this guide), we'll use a label. Add a label directly beneath Header Image and give it three constraints: pin it's top edge to the Header Image's bottom edge, it's top edge also to the Scrolling Content's top edge, and it's center X to the Scrolling Content's center X. The distance between the label's top edge and Scrolling Content's top edge will be the height of the image in the non-dragged state. This unfortunately needs to be set to a constant in the storyboard file -- we'll have to update it programmatically. More on that later.
The last part is easy: pin the leading and trailing edges of the Header Image to the leading and trailing edges of the Scrolling Content.
Now, all our constraints are in place! If you run the app, you can see how it's working correctly constraintwise, but the image isn't scaling the way we expect it to. A couple of last tweaks before we're done.
In the Attribute Inspector, under View, set the Mode of the Image View to "Aspect Fill". That gives it the correct parallaxy behavior.
To set the height of the Header Image correctly, we need a little bit of code. First, make an outlet from the constraint between the label's top edge and the Scrolling Content's top edge -- the one we set to a fixed value -- to your View Controller's source file. Call it imageHeightConstraint. Also add an outlet from the Image View called headerImageView. A good place to update the constraint programmatically is in the viewWillLayoutSubviews View Controller delegate method. Here is some code in Objective C:
- (void)viewWillLayoutSubviews {
[super viewWillLayoutSubviews];
CGSize imageSize = self.headerImageView.image.size;
CGFloat heightForWidth = imageSize.height / imageSize.width;
CGRect screenBounds = [UIScreen mainScreen].bounds;
CGFloat screenWidth = CGRectGetWidth(screenBounds);
self.imageHeightConstraint.constant = screenWidth * heightForWidth;
}
Finally, you may notice that when scrolling up, the label -- or whatever content is underneath the header view -- is getting covered by it. This is solved by checking Clip Supbviews on the Image View's Attribute Inspector.
Whew!
(Note: I began writing this as a question and then kept writing while I solved it for myself. I guess it would do well with a little text pruning and some images, but maybe it will help someone...)
My problem is slightly different from other's 'Swift UIScrollView' problems when using auto layout:
Problem:
Unlike others, when I run my app, it scrolls. My problem is that the scroll cuts off the bottom 20-30% of the content. I can pull to see the buttons did build and are down there, but when I let it go the scroll snaps back to a false bottom which cuts off my content!!! I've been trying, for days, to fix it to scroll the entire height but it continues to cut off!!
Description of app:
I used auto layout to layout 6 buttons and labels. Each button a rectangular image, with a label directly beneath it. (sorry, the site won't let me post pictures!)
I have my views arranged like this:
MainView > ScrollView > ContentView > Buttons & Labels
I have my contentView pinned to my ScrollView and my ScrollView pinned to my MainView. My buttons and labels all have constraints that are building correctly, to create a list that looks like:
Rectangular button
Label beneath it
Spacing
Rectangular button
Label beneath it
Spacing
Etc.
Can anyone tell me why I can't scroll the full length of the view?
Your description of how your items are constrained is vague, so I'm going to list all of the constraints you need to make this work. Then you can compare what you have to what you need and adjust accordingly.
Your ScrollView should be pinned on all 4 sides to the MainView. (This isn't absolutely necessary. You can constrain your ScrollView however you want, but make sure it can grow as the device and/or orientation changes).
Your ContentView should be pinned on all 4 sides to the ScrollView with offsets of 0.
Since you want your ScrollView to scroll vertically only, constrain the width of the ContentView to the width of the ScrollView using an Equal Widths constraint. To do this, in the Document Outline view, Control-drag from your ContentView to your ScrollView and select Equal Widths from the pop up.
The height of ContentView will be set by the sum total height of everything in it. In order for this to work, your topmost button needs to be pinned to the top of the ContentView, all of your buttons and labels should be pinned to their nearest neighbors, and the bottommost label should be pinned to the bottom of the ContentView. In addition, all of your buttons and labels should have constraints for their widths and heights. I would suggest setting an explicit width constraint and explicit height constraint for your buttons and centering them horizontally in the ContentView. For your labels, set an explicit height constraint and pin the left and right edges to the ContentView.
If you have these constraints and no other ones, your ContentView will be properly sized.
Using contentView, like you said, usually fixes the issue. So chances are you need to take a second look at your contraints. Maybe try this solution in a clean/new project to see that it works. (it does work). My guess would be that some of your constraints conflict each other.
Otherwise I think it would be a good idea to setContentSize of your scrollView in your viewDidLoad.
Another hack would be to place 2 UI objects with their alphas set to zero on the right top corner and left bottom corner. This would hint scrollView to set its contentSize.
I have a viewController, which is configured for the iPhone5 screen size. In red rectangle is the view.
To make this view show properly in iPhone4 - I used auto layout. But when I specify constrains such as: leading edge, trailing edge, bottom space and top space (in top space I even made constraint's priority to LOW ) - the view still goes partially down the screen as if my constraints don't work.
BUT if instead of top space constraint I specify view's heigh and delete top space constraint - everything works perfectly.
Does anyone can explain it please? Thank you.
Thats because when you set up the top space constraint it will move the view by the constant you provided. iPhone 4 and iPhone 5 screen height is different but the constant remains the same so obviously it will behave differently. One way to troubleshoot your interfaces is to switching between iPhone4 and iPhone 5 on storyboard device on storyboard (first button from left to right on the bottom right corner of interface builder).
Auto-layout is all about experience in my opinion. I struggled alot with it until i learned. If you want your view to be attached to the bottom of the screen you should set the BOTTOM SPACE to 0 and specify the view's height like you did or adjust constraints for it's subviews so that the height is set dinamically according to the views inside.
So all I'm trying to do is put an imageview at the foot of the screen. Before iOS6 autolayout I could just hit the bottom "I" and it would hold it to the bottom and push it up if the screen got short (i.e. if the screen size went from 568 to 480 points tall). But now I have been trying to add a bottom spacing to Superview at 0 but I can't seem to do anything to get rid of the the top spacing constraint to stop messing me up. If I convert the top spacing to a user constraint and then delete it then (thinking that the vertical constraint would be handled by the bottom spacing) but it auto re-creates that contraint... any ideas?
Update It seems it was due to the fact that I was having it be a subview of a scrollview (was going to use it for scrolling horizontally, not vertically). Anyone know why it wont let me do that? Seems like you should still be able to constraint to the bottom of a scroll view.
It could be that the Button's constraints are somehow wrong. Having the height, width, bottom distance and horizontal centering should be enough to define its position. Try deleting the button and centering the image view on the super view instead, and see if tha allows you to delete that top constraint.