I've two views (Text/Image) where one covers the total width of the screen, the other one is an image which sits in lower right corner of the text view.
Up to now I was not able write layout constraints to have both view right and bottom aligned to each other. Here is what I tried to accomplish it but the statusA1 is incorrect.
NSArray *horizontalA = [NSLayoutConstraint constraintsWithVisualFormat:#"H:|[answerA]|" options:0 metrics:nil views:viewsDict];
NSArray *statusA1 = [NSLayoutConstraint constraintsWithVisualFormat:#"[answerA][statusA]" options:NSLayoutFormatAlignAllBottom | NSLayoutFormatAlignAllRight metrics:0 views:viewsDict];
Set the vertical spacing between two and remove the bottom contraints on both the subviews.
Related
I am new to IOS and I am adding constrain to my added view with using constraintsWithVisualFormat. I already use constraintsWithVisualFormat to have vertical spacing by these following code:-
self.underlineConstraints = [NSLayoutConstraint
constraintsWithVisualFormat:#"V:[view]-80-[underlineView(5)]"
options:NSLayoutFormatAlignAllLeading | NSLayoutFormatAlignAllTrailing
metrics:nil views:views];
Here 5 is height of underlineView and 80 is space between two views but I want to add constrain of width of underlineView 150.
To add width constraints:
[self.view addConstraints: [NSLayoutConstraint
constraintsWithVisualFormat:#"H:[underlineView(150)]"
options: kNilOptions
metrics:nil views:views]];
I'm using auto layout, programmatically. I've got a simple UIViewController with a few controls, including two UIButtons arranged side-by-side. I often group related controls within a UIView, to act as a container, making the arrangement of groups-of-controls a bit easier to manage. You'll see that below with _iapButtonsView, which holds the two buttons and some spacers.
My question. In the following example, I was caught out by what I thought was a valid change to the constraints, that actually resulted in the UIButtons not receiving touch events.
Code extract - constraints in which the buttons do receive touch events:
- (void)viewDidLoad
{
[super viewDidLoad];
...
_buyButton = [ViewCreationHelper createRoundedBorderButtonBold];
[_buyButton addTarget:self action:#selector(buyTap:) forControlEvents:UIControlEventTouchUpInside];
_restoreButton = [ViewCreationHelper createRoundedBorderButton];
[_restoreButton addTarget:self action:#selector(restorePurchaseTap:) forControlEvents:UIControlEventTouchUpInside];
_iapButtonsView = [UIView new];
_iapButtonsView.translatesAutoresizingMaskIntoConstraints = NO;
[contentView addSubview:_iapButtonsView];
...
[_iapButtonsView addSubview:_buyButton];
[_iapButtonsView addSubview:_restoreButton];
// Constraints
NSDictionary* views = NSDictionaryOfVariableBindings(scrollView, contentView, iapDesciption, _iapButtonsView, _buyButton, _restoreButton, spacer1, spacer2, spacer3);
...
constraints = [NSLayoutConstraint
constraintsWithVisualFormat:#"V:|-25-[iapDesciption]-40-[_iapButtonsView]|"
options:0
metrics:nil
views:views];
[contentView addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:#"H:|-20-[_iapButtonsView]-20-|" options:0 metrics:nil views:views];
[contentView addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:#"H:|[spacer1][_buyButton(==120.0)][spacer2(==spacer1)][_restoreButton(==_buyButton)][spacer3(==spacer1)]|" options:NSLayoutFormatAlignAllCenterY metrics:nil views:views];
[_iapButtonsView addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:#"V:|[_buyButton(==80.0)]|" options:0 metrics:nil views:views];
[_iapButtonsView addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:#"V:|[_restoreButton(==80.0)]|" options:0 metrics:nil views:views];
[_iapButtonsView addConstraints:constraints];
...
}
The constraints in question are the vertical constraints for _iapButtonsView. During development (this is an In-App Purchase screen) I had some debug controls at the bottom, which is why I had the trailing | connecting to the superview's bottom edge, like this:
constraintsWithVisualFormat:#"V:|-25-[iapDesciption]-40-[_iapButtonsView][someSpacer][someControls]|"
When I took those debug controls out, I changed those constraints to be:
constraintsWithVisualFormat:#"V:|-25-[iapDesciption]-40-[_iapButtonsView]"
thinking that was more correct: they're anchored from the top, only, the _iapButtonsView gets its size from its subviews (principally, the two buttons), so I shouldn't connect to the bottom edge of the superview...
With that change, the buttons no longer receive touch events. To experiment, I tried explicitly setting the vertical size of _iapButtonsView, but still not connecting to the bottom edge of the superview, e.g.
constraintsWithVisualFormat:#"V:|-25-[iapDesciption]-40-[_iapButtonsView(==80.0)]"
With those constraints, the buttons still do not receive touch events.
What am I not understanding?
(Edit: I removed the duplicated [contentView addSubview:_iapButtonsView]; in the code, above, per suggestion from daddy warbucks)
One issue, you've called this two times:
[contentView addSubview:_iapButtonsView];
Not sure if this helps, but it could be an issue.
Also, you don't have to use "(==80.0)", just use "(80.0)", or even "(80)" not sure if this helps, but hey, it could, right?
Here is my structure of views for this detail view (blogging application, I want to view the entire post which has dynamic height inside of a scrollview):
UIView
-UIScrollView
-SinglePostView (custom view)
-Title
-Subtitle
-Content
Normally to add a 'single post view' to a UIView I simply instantiate it, feed it my Post object and then add a single constraint that pins the width of the singlePostView to the superview, at which point things get laid out nicely. However when I try to add it to a scroll view, it doesn't show up nor does it scroll.
UIScrollView *scrollView = [[UIScrollView alloc] init];
[self.view addSubview:scrollView];
NOBSinglePostView *singlePost = [[NOBSinglePostView alloc] initWithPost:self.post];
[scrollView addSubview:singlePost];
singlePost.translatesAutoresizingMaskIntoConstraints = NO;
scrollView.translatesAutoresizingMaskIntoConstraints = NO;
NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings(scrollView,singlePost);
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[scrollView]|" options:0 metrics: 0 views:viewsDictionary]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[scrollView]|" options:0 metrics: 0 views:viewsDictionary]];
[scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[singlePost]|" options:0 metrics: 0 views:viewsDictionary]];
In the structure you are presenting, using AutoLayout, the contentSize of your UIScrollView is driven by the intrinsicContentSize of its subviews, here your SinglePostView.
The problem is, SinglePostView being a subclass of UIView, its intrinsicContentSize is always CGSizeZero when considered by itself. What you need to do is make the intrinsicContentSize of your SinglePostView depend on the intrinsicContentSize of its subviews.
Then, because the subviews of your SinglePostView are UILabels, and because a UILabel's intrinsicContentSize is the smallest size it needs to display its content, your SinglePostView's intrinsicContentSize will be equal to the sum of its subviews intrinsicContentSizes, that is the total size needed to display the content of all three of your labels.
Here is how to do it.
Step 1: Removing all automatically set constraints
First, as you partially did, you need to remove all constraints automatically set by the system.
Assuming you don't have any constraints set in your storyboard or XIB (or you don't even have one of these), just do:
scrollView.translatesAutoresizingMaskIntoConstraints = NO;
singlePost.translatesAutoresizingMaskIntoConstraints = NO;
titleLabel.translatesAutoresizingMaskIntoConstraints = NO;
subtitleLabel.translatesAutoresizingMaskIntoConstraints = NO;
contentLabel.translatesAutoresizingMaskIntoConstraints = NO;
Now you have a clear slate and you can start setting your own constraints.
Step 2: Constraining the scrollView
First, let's create, as you did, the views references dictionary for AutoLayout to use:
NSDictionary *views = NSDictionaryOfVariableBindings(scrollView, singlePost, titleLabel, subtitleLabel, contentLabel);
Then, also as you already did, let's constrain the scroll view to be the size of its superview:
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|-0-[scrollView]-0-|" options:0 metrics:0 views:views]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|-0-[scrollView]-0-|" options:0 metrics:0 views:views]];
Step 3: Constraining the SinglePostView to push the scrollView's contentSize
For this step to be clear, you have to understand that every constraints set between a UIScrollView and its subviews will actually change the contentSize of the UIScrollView, not its actual bounds. For Example, if you constrain a UIImageView to the borders of its parent UIScrollView and then put an image twice the size of the UIScrollView inside the UIImageView, your image won't get shrunk, its the UIImageView that will take the size of its image and become scrollable inside the UIScrollView.
So here is what you have to set here:
[scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|-0-[singlePost]-0-|" options:0 metrics:0 views:views]];
[scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|-0-[singlePost]-0-|" options:0 metrics:0 views:views]];
[scrollView addConstraint:[NSLayoutConstraint constraintWithItem:singlePost
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:scrollView
attribute:NSLayoutAttributeWidth
multiplier:1.0f
constant:0.0f]];
First two constraints are pretty obvious. The third one, however, is here because, for your UILabels to display their content properly and still be readable, you will probably want them to be multilined and the scrolling to be vertical, not horizontal. That's why you set your SinglePostView's width to be the same as your scrollView's. This way, you prevent your scrollView's contentSize.width to be anything more than its bounds.width.
Step 4: Constraining your UILabels to "push" the bounds of your SinglePostView
Fourth and final step, you now need to set constraints on your SinglePostView's subviews, so that it gets an intrinsicContentSize from them.
Here is how you do it (simplest implementation, no margins, one label after the other vertically):
[singlePost addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|-0-[titleLabel]-0-|" options:0 metrics:0 views:views]];
[singlePost addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|-0-[subtitleLabel]-0-|" options:0 metrics:0 views:views]];
[singlePost addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|-0-[contentLabel]-0-|" options:0 metrics:0 views:views]];
[singlePost addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|-0-[titleLabel]-0-[subtitleLabel]-[contentLabel]-0-|" options:0 metrics:0 views:views]];
And with that you should be done.
One last advice, you should definitely look into UIStoryboard to do these kinds of things. It's a lot simpler and more visual.
Hope this helps,
P.S.: If you want, I can take some time and push a project using both UIStoryboard and the Visual Format Language on Github. Just tell me if you would need one.
Good luck.
in auto layout
frame of scrollview is decided by constraints between scrollview and superview of scrollview.
contentSize of scrollview is decided by constraints between scrollview and subview of scrollview.
you should set the size of singlePostView. ScrollView calculate contentSize from it. (you need to add size constraints explicitly)
CGFloat heightOfSinglePostView = calculate..
[scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[singlePost(heightOfSinglePostView)]|" options:0 metrics: 0 views:viewsDictionary]];
I've got a UIView with a UILabel subview that has constraints defined like so:
constraints = [NSLayoutConstraint constraintsWithVisualFormat:#"H:|-10-[_messageLabel]-50-|" options:0 metrics:nil views:views];
[self addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:#"V:|-0-[_messageLabel]-0-|" options:0 metrics:nil views:views];
[self addConstraints:constraints];
In certain instances, the label is not big enough to show all the text, so it is truncated.
When I adjust the size of the UIView within an animation block, the label animates its change in size as appropriate. However, the re-drawing of the text within it kind of 'jumps' -- and fair enough, i wouldn't expect the label to animate a change in the internal drawing of its text.
Anyway, what I'd like to do is fade out this label and perhaps fade in a second to avoid this jerkiness.
My question: Is there a good callback on UIView as to when it will respond to an auto layout change? or is that simply done in layoutSubviews?
I want an iPad layout that that has two panels side by side, to fill the width of the screen and both are as tall as the screen. My attempts have led to as follows
self.view addConstraints:
#"|[_sidePanel(300)]-1.0-[_mainPanel]|"
#"V:|[_sidePanel]|"
#"V:|[_mainPanel]|"
Inside __sidePanel_ I'm trying to create more constraints on child views.
Note the _sidePanel view is a UIScrollView.
I want to stack 2 views on top of one another in the side panel.
So I add the following constraints to__sidePanel_.
_sidePanelView addConstraints:
#"|[_top(300)]|"
#"|[_bottom(300)]|"
#"V:|[_top]-5.0-[_bottom]|"
It seems I need to specify the width for these two views in order to avoid ambiguity.
But I want the bottom view to fill the remaining space of __sidePanel_.
If I just pin __bottom_ to the bottom of __top_ (which gets a defined height at some point based on its contents) and to the bottom of its parent __sidePanel_, the __sidePanel_ and __bottom_ are both ambiguous; which makes sense i guess since the constraints are awfully similar (and which doesn't get avoided by adding the constraint for __bottom_ to the __sidePanel_ view as opposed to the topmost self.view).
If I hardcode a height for __bottom_, i resolve ambiguity but I don't want a defined height; i want it to fill remaining space in __sidePanel_.
Any suggestions on what I could try to resolve ambiguity but still achieve what I'm after?
You need to specify a height for either top or bottom -- it sounds like top gets a defined height at some point, but you need set a defined height for it initially, which you can change later.
Also, there's no need to specify the widths (300) for either top or bottom, since you've pinned them to the sides of sidePanel, which itself has a defined width. so these constraints worked fine with no ambiguity:
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"|[_sidePanel(300)]-1.0-[_mainPanel]|" options:0 metrics:nil views:viewsDict]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[_sidePanel]|" options:0 metrics:nil views:viewsDict]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[_mainPanel]|" options:0 metrics:nil views:viewsDict]];
[_sidePanelView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"|[_top]|" options:0 metrics:nil views:viewsDict]];
[_sidePanelView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"|[_bottom]|" options:0 metrics:nil views:viewsDict]];
[_sidePanelView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[_top]-5.0-[_bottom]|" options:0 metrics:nil views:viewsDict]];
self.topHeightCon = [NSLayoutConstraint constraintWithItem:self.top attribute:NSLayoutAttributeHeight relatedBy:0 toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:300];
[self.top addConstraint:self.topHeightCon];
Later, when you calculate the actual height for top, you can use self.topHeightCon.constant = (some value) to adjust its height.
In my case it came down to the fact that the view I was trying to have subviews constrain to its bounds was a UIScrollView, which wasn't happening. I since changed it to a UIView and voila my constraints work. And there you have it.