I’ve been asked this question on a job interview and I’m wondering what he meant.
The role of hugging and compression properties for any view with intrinsic content size is obvious.
But what about views without intrinsic content size? Do they play a role there?
Kind of an odd question, without some additional context.
However, I suppose you could discuss a couple things...
Some views get an intrinsic content size after-the-fact. A UIImageView, for example... without an image, it has no intrinsic content size. But once you set its .image property, its intrinsic content size will be the size of the image. So, you may want to set the priorities based on what will happen.
You can give a UIView, for example, "Placeholder" intrinsic content size. Changing the hugging/compression priorities will affect that view during design-time.
In both of those cases, you would be "planning ahead" during Storyboard / IB design for what you want at run-time.
EDIT
Here is a (rather long) example:
Here I have a UIView (green) containing a UIStackView set to Fill / Fill / 8. The stack view holds a UIImageView (Scale To Fill) and a UILabel. The image view has NO intrinsic content size, while the label has an intrinsic content size, based on its content.
With the constraints I've set, the stack view is 200 x 240 points.
At run-time, I'm going to set the image to a 200 x 100 png of a cat:
My goal is for the image view to "fit to the image," letting the label expand vertically.
When I set the .image via code (at run-time), the image view "gets" an intrinsic content size (of 200 x 100 in this case). With both the image view and the label having Vertical Content Hugging: 251 (the default), this is the result:
But I want the image to retain its original aspect ratio of 2:1. First thought is to change the image view's Content Mode to Aspect Fit -- but I get this result:
Now my image view is "letter-boxing" the image, showing the red background color.
So, I change the image view's Vertical Content Hugging: 252 (higher priority than the label). The output:
Now I have the run-time output that I want, but at design-time (working in Storyboard / IB), nothing has changed and it may not really be clear what's going to happen.
So, I give the image view a Placeholder intrinsic content size of 200 x 100, and I see this:
Because it's a placeholder, that will have no effect on the run-time output (if I set the image to a 200 x 50 image it will be 200 x 50 at run-time), but it better reflects what I'm expecting.
Of course, there are other ways to accomplish the goal, and this may not be the ideal approach, but it (hopefully) gives an idea of one way that setting Hugging / Compression priorities on elements with no intrinsic content size can be useful / needed.
Related
I am working to have my buttons height and position adapt to screen size changes like the pictures shown above. The buttons themselves will remain clear and only serve as a simple way to handle taps that trigger the segues to different screens. My goal is to make it so that as the image stretches across different screen sizes, I would like the buttons to keep equal height and width and position with the windows. I know that if the windows had properties I could simply make the buttons have an equal size and width to them and be done, but as I mentioned the image is static and it has to stay that way for the time being. I've tried creating constraints for the buttons and that has only proven to be a headache and I don't know if stack views will help me here either, I know this is fairly complex, but I'm ok with that I just need some direction.
UPDATE: In an effort to follow the instructions LGP listed properly I started from step 1. As I mentioned in the comments, I believe it's simply the ratio and the constraints conflicts since when I remove one or two it works fine, but then how do I set the constraints so it fills the entire screen and maintains the ratio of the picture? Also shown are the constraint conflicts for the image view an it isn't showing the aspect ratio of the parent container view either
If you want to do it in interface builder it is not too hard. You should use spacer views and proportional sizes to position the buttons. That way, whatever size your background will have, all the elements will follow.
1. Create a container that has the same proportions as you image. Add a regular UIView and set an Aspect Ratio constraint with a multiplier of 852:568. This is the dimension of your background photo, 852 x 568 pixels, but the actual values don't matter, as long as the aspect ratio is the same. (Don't forget to also tie up the container view to however you want it in your view controller. See the UPDATE below on how to do this.)
2. Place the background image in the container. Add an image view as a child to the container. Set the constraints to touch all four edges of the container. Set the Image property to you image, and set Content Mode to Aspect Fit.
3. Add the first spacer view. Add a regular UIView to the container view (see leftmost, white view below) and set the constraints as follows:
height = 1 (not important, I used 10 in the image)
Top space to Superview = 90 (not important)
Leading space to Superview = 0
Width equal to Superview with multiplier dw:cw <- This makes it proportional! dw is the distance from the left edge to the first window/button, and cw is the width of the container. If your container is 375 wide, and your distance to the first button is 105, the multiplier will be 105:375.
4. Add the second space view. This is the vertical spacer, going from top to first button. Set it up similar as the first spacer, except make the height proportional to the containers height, and the width fixed.
5. Add the first button. Constrain its left and top edges to the spacers, then make its width and height proportional to the container.
6. Add the remaining spacers and buttons. They are all the same. Just remember where to make them proportional. All buttons are constraint to the single vertical spacer.
Finally, you should make the spacer views hidden. You can easily try it within your Storyboard by selecting different devices.
I chose to add everything on iPhone 8, but it is not really important. Here is what it looks like when I change to iPad Pro 12.9" and iPhone SE. Note how the buttons are positioned correctly. The spacer move around a little because they have partly fixed distances, but it works fine anyway.
UPDATE: Here is how to constrain the container view in the view controller's view to make the container fill the whole view and still keep its aspect ratio.
First, set the image view's (the one you added in step 2 above) Content Compression Resistance Priority to 200 for both Horizontal and Vertical. This will allow the image to compress rather then expand if it has a choice.
Second, Add the following constraints to you container:
Align Center X to Superview
Align Center Y to Superview
Equal Width to Superview >= 0
Equal Height to Superview >= 0
852:568 Ratio to View <- This you should already have!
Now the container will always center on screen, it will always fill at least the entire screen, but will also allow it to fill beyond in both X and Y.
UPDATE 2: If you want to ignore the photo's aspect ratio, and always fill the screen with the photo, you just add constraints for the container view to each side to its superview. Your container view's constraints should look like this.
In step 2 you will need to set the image's Content Mode to Scale to fill. The rest should be the same.
Use percentage based positions and size. Identify the positions of windows in percentage basis, and create the origin in x and y dimension by multiplying the percentage to the width and height of the screen. I am assuming that you are using ScaleToFill as content mode of the ImageView.
Similarly for calculating size, identify the width and height of the ImageView on percentage basis, and multiply the values in percent with the total width and height of the screen.
For example, to calculate the position of Window one-
Suppose, window1.x in percentage basis is 25% & total image view width is 400 (for example), than window1.x pixel position will be-
window1X = (25 * 400) / 100 = 100
Suppose, window1.y in percentage basis is 25% & total image view height is 300 (for example), than window1.y pixel position will be-
window1Y = (25 * 300) / 100 = 75
Suppose, width is 7% of image views width, than width in pixel will be -
window1Width = (7 * 400) /100 = 28
Suppose, height is 12% of image views height, than height in pixel will be -
window1Height = (12 * 300) /100 = 36
window1.frame = CGRectMake (window1X, window1Y, window1Width, window1Height)
Same approach for other windows, to calculate their positions(size will be same as window 1)
This approach will work across all screen resolutions, since it uses percentage based calculations & ScaleToFill as content mode for image view.
I am a beginner, I am trying to do an autolayout. I am trying to make the label 'HRIS' and 'Please login to continue' to be proportional to the screensize (its superview), I can do it for the login button and the image leaf as the picture above, we can see that the login button and leaf image are proportional.
for the image leaf, I do equal width with 0,1 multiplier to the superview, and then I also add 'aspect ratio' to make it proportional.
but when I apply the same way to the label, it doesn't work, as we can see the label size still the same for iphone 4s and iphone 8, maybe it is because the instrinsict content size (the font size itself) that makes it like that. I tried to apply this way, but it seems the size is still the same
I want to make it little bit smaller for iphone 4s, I also can't modify using size classes since it is in the same class
so what I have to do to make label proportional to the superview (screen size / background) ?
You can do it by setting both proportional width of the label and allow it to scale down the point size.
Set the label width to proportional width like this. It is just a regular same width constraint that you edit.
Then allow your label to scale down the point size like this. This is a property of your label.
Set different font size using variations...
Simply set up a constraint for your label's width to be equal the view's width with your desired multiplier. In my example I used a multiplier of 0.5:
I have 4 views and I want them to occupy 40 %,15%,15%,20% and I want 2 % space among them and 2% space to top and bottom layout.
I am confused on what constraint to use and how to use ?
like can aspect ratio be used for this like that ?
If I could set it in px I can do easily ,but its percetage there it gets tricky
Is it possible if i set it in px it will get translated to percentage according to screen size
Regards,
Appu
You can use the Equal constraint and set the percentages in the multiplier.
Assuming you have 1 view controller and 1 view in it, control + click (or right click) and drag from view to view controller, and choose equal (width | height).
After that, go to the size inspector on the right side and click edit on the constraint you just added and change your multiplier.
Unrelated:
Aspect ratio is when you want to constrain the size of a view to a certain ratio (W:H). 1:1 would mean width is equal to height. 1:3 means height is 3 times your width.
Size classes is when you want to use different designs for different devices sizes. Read more on size classes here
I am trying to create this layout, but I am struggeling so badly that I have no words left for it. I have tried for three days but yet I can't create the layout.
I am trying to have the three imageviews in the middle scale if the height of the view changes, but they are not behaving correct. I have successfully manage to get the ratios correct though, but the images either goes behind the blue button, or the blue button suddenly looses its height or the text disappears.
Isn't it possible to have three image views in the middle that take whatever height is left after the title and text + blue button have been laid out and then properly show them with correct ratios?
You can try multiple approaches here:
Size Classes:
Lay out the views for each possible size (probably the easiest but the least flexible
Use Constraints with different priorities:
You can set a max-height for the image views by adding a constraint for the height and then setting its relationship to equal or less than. This allows the image to scale up until a maximum size is reached.
Then add a second constraint between the bottom box and the images. Set the priority of this constraint to 750. This makes the image grow in height, when the bottom view moves down.
Then add another constraint which sets the aspect ratio of the image. If you use the mode of the view to Aspect Fit, the image will now always be scaled up to fit the image view.
To make all images scale proportionally, add constraints for equal width and equal height between them, then set the factor to match the proportions between these images.
The last step is now to vertically align the images properly as you showed in the pictures. To do that, add constraints between the images, which align them by their vertical centers, bottoms, baselines or tops.
I have a UILabel which autoresizes along with its parent view. The label has AdjustsFontSizeToWidth turned on and has a minimum text size of 0 - so basically it tries to fit all the text into whatever size the UILabel is.
The problem I am having is that vertically the text gets cut off. So yes, the label is adjusting its font size to the width of the label but the text is too tall for the label and thus some of the text is getting cut off.
Is there anyway to work around this so that all of the text, the full height and full width are shown?
I attach an image to show what I mean. The red box is the parent view, the purple box is the UILabel.
Thanks for your help.
What you are adjusting automatically is the Width and not the Height. The Height is something you'll have to adjust manually based on the maximum font size you will use. If the maximum (assigned initial) font size fits in height, so will the smaller one's do, after they are automatically adjusted
I suspect that Lefteris is right, that minimum text size focuses on font size for the width of the control. Note, though, if you want it to resize the font to fit, you want a non-zero minFontSize. See minimizeFontSize notes. Also check out the various NSString UIKit Additions that can be used to get the size of the control necessary to fit your text, and programmatically adjust the size (i.e. the frame) your UILabel accordingly.
In my case there was a bogus vertical centering of a view under the labels being clipped and squashed. That somehow took priority over compression resistance priority of 1000 for the labels. No warning on console about conflict though. But the view debugger was of some help.