i use autolayout without sb and xib.But i have some problems recently.
i don't understand which view should i use to implement the following two methods
- (void)addConstraint:(NSLayoutConstraint *)constraint
- (void)addConstraints:(NSArray<__kindof NSLayoutConstraint *> *)constraints
for example,i have a super view as following:
_menuView = [[UIScrollView alloc] init];
_menuView.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:_menuView];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|-0-[_menuView]-0-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_menuView)]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|-0-[_menuView(40)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_menuView)]];
and two subViews:view1,view2.When i use autolayout to add constraints to describe view1 and view2,
[WHICHVIEW addConstraint:<#(nonnull NSLayoutConstraint *)#>];
or
[WHICHVIEW addConstraints:<#(nonnull NSArray<__kindof NSLayoutConstraint *> *)#>];
what should WHICHVIEW should be?
Let me put it another way,is WHICHVIEW depend on the relationship between view1 and view2?what if view1 is not the same hierarchy as view2?
WHICHVIEW should be a parent of [all] the items you are trying to constrain. So if you are adding a number of views to a scrollview and trying to constrain them, with respect to themselves and to the scrollview, the scrollview should be WHICHVIEW. If view1 and view2 are not at all in the same hierarchy, then you cannot add a constraint between the two.
Do not use any WHICHVIEW. Do not call addConstraints:. Call NSLayoutConstraint.activateConstraints instead. It has the advantage that it does all that work for you - it adds the constraints to the correct views, automatically.
Related
I know there is are similar topics, but i cant figure out how to do simple thing, for example, set view frame programmatically with Auto Layout constraints. Its pretty easy to do with Storyboard, but when i try to learn about NSLayourConstraint i realise that i'm not understand topic.
Consider that we have UIView and 3 buttons. First button at top have 3 constraints (leading and trailing, and to top of a view). Other 2 buttons centered horizontally with that button and have equal widths. its pretty easy layout, i upload screenshot:
I have read about visual format language, but what i cant understand is - how to create constraint, for example, that relay to top (or trailing-leading)? Like following:
Task look pretty simple but still, i did not found a way how to do that programmatically with NSLayoutConstraint. Could you please provide a solution? Thanks.
Here's a solution (should go in -viewDidLoad). There are a a couple of things to note:
Firstly, VFL doesn't allow you to create all possible types of constraint. In particular, centering needs to be done with the +constraintWithItem: class method on NSLayoutConstraint.
Secondly, as noted in the comments, you could just use hardcoded left and right pad values in the horizontal VFL string to achieve the centering, but this might cause problems if you need to support different device sizes.
Thirdly, the call to -setTranslatesAutoresizingMaskIntoConstraints: is critical. Programmatic Autolayout will completely fail to work if you forget this. Also you need ensure all views are added to their superviews before setting up constraints, otherwise any constraint string referencing a superview will cause a crash
NSArray *names = #[#"button1",#"button2",#"button3"];
NSMutableDictionary *views = [[NSMutableDictionary alloc]init];
for(NSUInteger i=0;i<3;i++) {
UIButton *b = [[UIButton alloc]init];
NSString *name = names[i];
[b setTitle:name forState:UIControlStateNormal];
views[name] = b;
[b setBackgroundColor:[UIColor redColor]];
[b setTranslatesAutoresizingMaskIntoConstraints:false];
[self.view addSubview:b];
}
//List of values to be used in the constraints
NSDictionary *metrics = #{
#"buttonWidth":#150,
#"bHeight":#50, //button height
#"topPad":#100,
#"vPad":#20 //vertical padding
};
//Horizontal VFL string (repeated for all rows).
for (NSString *buttonName in views.allKeys) {
NSString *horizontalConstraintString = [NSString stringWithFormat:#"|-(>=0)-[%#(buttonWidth)]-(>=0)-|",buttonName];
NSArray *horizontalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:horizontalConstraintString options:0 metrics:metrics views:views];
[self.view addConstraints:horizontalConstraints];
//Can't do centering with VFL - have to use constructor instead. You could also hardcode left and right padding in the VFL string above, but this will make it harder to deal with different screen sizes
NSLayoutConstraint *centerConstraint = [NSLayoutConstraint constraintWithItem:self.view attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:views[buttonName] attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0.0];
[self.view addConstraint:centerConstraint];
}
//Vertical VFL (vertical spacing of all buttons)
NSString *verticalConstraintString = #"V:|-topPad-[button1(bHeight)]-vPad-[button2(bHeight)]-vPad-[button3(bHeight)]-(>=0)-|";
NSArray *verticalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:verticalConstraintString options:0 metrics:metrics views:views];
[self.view addConstraints:verticalConstraints];
[self.view layoutIfNeeded];
I'm adding a login view in my tableview. But as you can see on the image below it doesn't look great.
I am using auto layout for both the tableview and the loginview.
For the loginview I have the constraints showed on the image below, but what's strange(to me) is that these constraints seem to be valid for both the Green View and its superview (the black). Because, when I change it for one of them, it changes for the other as well.
Note: The loginview has separate a controller, but the controller is not presented. The loginview is just added to the tableview.
Any suggestions?
From what I can see in this image, there are 4(!) views you need to account for.
1.) the superview
2.) the UITableview
3.) the black view
4.) the login-view (blue-green?)
It looks like the constraints for (4) are set correctly in relation to (3)
To me, I'd examine the constraints for (3) in relation to (1).
In other words make sure the leading/trailing top/bottom constraints are all 0 or to margin in relation to the superview, and you should be good to go.
Here is a quick example on how you could implement this. This assumes you are using view controller containment, which you should be.
child is your signIn view and self is the Table view controller
// Add login view to my view
[self addChildViewController:child];
child.view.frame = self.view.bounds;
[self.view addSubview:child.view];
[child didMoveToParentViewController:self];
// Add constraints
NSDictionary * views = #{#"view" : child.view, #"super" : self.view};
NSArray * hConstraints = [NSLayoutConstraint constraintsWithVisualFormat:#"H:|-[view]-|" options:0 metrics:nil views:views];
NSArray * vConstraints = [NSLayoutConstraint constraintsWithVisualFormat:#"V:|-[view]-|" options:0 metrics:nil views:views];
[self.view addConstraints: [hConstraints arrayByAddingObjectsFromArray:vConstraints]];
When I'm doing the initial setup of a UIView's subviews, if I initialise a UIView:
//Listing A
UIView *redBox = [[UIView alloc] init];
[redBox setBackgroundColor:[UIColor redColor]];
[self.view addSubview:redBox];
[redBox setTranslatesAutoresizingMaskIntoConstraints:NO];
And I want to programmatically apply Auto Layout constraints to it:
//Listing B
NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:#"H:|-[redBox(100)]" options:0 metrics:nil views:#{#"redBox": redBox}];
[self.view addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:#"V:|-[redBox(100)]" options:0 metrics:nil views:#{#"redBox": redBox}];
[self.view addConstraints:constraints];
Where should Listing B go?
Should it always immediately follow Listing A?
Or, if we're in a UIView subclass, should it go into:
updateConstraints
initWithFrame or
layoutSubviews ?
Similarly, if we're in a UIViewController subclass, and I place Listing A in viewDidLoad, should Listing B immediately follow it or should it go into:
initWithNibName:bundle:
viewWillLayoutSubviews or
updateViewConstraints ?
I often put it all in a method (or series of methods) called setUpConstraints or something like this.
Then I call that method from viewDidLoad.
If you're doing it in a UIView then I call my setupConstraints method from the init methods and awakeFromNib.
Having said that the method updateViewConstraints is already provided for you for this purpose so you could call your setupConstraints method from there.
viewDidLoad is the best place to apply the custom layout because it will not conflict with xib constraint at initialisation!
I'm fairly new to iOS programming and probably don't understand the view hierarchy as well as I should and thus am failing to successfully get two labels within a custom table cell class I have created to autoresize properly. Namely the "translatesAutoresizingMaskIntoConstraints" property has me a little confused.
I am not using storyboards for this part of the code: I have a TableViewController where I create my own tableView in viewDidLoad. In cellForRowAtIndexPath I init my own TableViewCell implementation.
The problem I'm having is that when I set "setTranslatesAutoresizingMaskIntoConstraints" to NO for the table view and the UILabels I create then add my constraints, I get the following error:
"Terminating app due to uncaught exception `'NSInternalInconsistencyException',` reason: 'Auto Layout still required after executing `-layoutSubviews`. UITableView's implementation of `-layoutSubviews` needs to call super.'"
If I comment out the setTranslatesAutoresizingMaskIntoConstraints lines, my app runs however I get the following warning about the constraints:
"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)"
Essentially what I want to do is to enter code here have the two labels flush against each other and for them to resize based on orientation/device (I will be setting a background colour on them so want them to look 'continuous')
Can anyone help me out and explain what I am missing? Thanks in advance.
My code for adding the labels is:
self.nameLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 200.0f, 30.0f)];
self.nameLabel.textColor = [UIColor redColor];
self.nameLabel.font = [UIFont fontWithName:#"Helvetica Neue" size:12.0f];
self.nameLabel.backgroundColor = [UIColor brownColor];
[self.nameLabel setText:#"Test"];
// [self.nameLabel setTranslatesAutoresizingMaskIntoConstraints:NO];
[self.contentView addSubview:self.nameLabel];
...
NSDictionary *viewsDictionary =
NSDictionaryOfVariableBindings(nameLabel, summaryLabel);
NSArray *constraints =
[NSLayoutConstraint constraintsWithVisualFormat:#"|-[nameLabel][summaryLabel]-|"
options:0
metrics:nil
views:viewsDictionary];
I'm fairly new to ios programming and probably don't understand the
view hierarchy as well as I should and thus am failing to successfully
get two labels within a custom table cell class I have created to
autoresize properly. Namely the
"setTranslatesAutoresizingMaskIntoConstraints" property has me a
little confused.
Well, translatesAutoresizingMaskIntoConstraints is a property that is created by Apple to make the transition from Autoresizing (Spring and Struts) to Autolayout easier. Say, you had some AutoresizingMasks for your view and you just switched Autolayout ON without setting any constraints. Then your existing AutoresizingMasks will get converted into constraints which will hold the view in place. So, by default translatesAutoresizingMaskIntoConstraints property is set to be YES. However, when you start adding constraints, in 90% cases they will conflict with the constraints that got created by converting your AutoresizingMasks. So, it is better to turn it off by setting view.translatesAutoresizingMaskIntoConstraints = NO
In your code, the following might have been creating the problems:
The setting of Frame
You should not set frames to objects which you will be adding constraints to. It's a paradigm shift. When you think in Autolayout way, frames are but effects of setting right constraints who combinedly determine the frame of the view in question.
So, please remove the frame setting.
self.nameLabel = [[UILabel alloc] init]; will suffice.
Setting proper constraints
Your Code:
NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings(nameLabel, summaryLabel);
NSArray *constraints =
[NSLayoutConstraint constraintsWithVisualFormat:#"|-[nameLabel][summaryLabel]-|"
options:0
metrics:nil
views:viewsDictionary];
NameLabel
Now, the above constraints tells us the nameLabel should be horizontally (as you have not mentioned H: or V:) spaced "standard" distance (20px) from container, adjacent to the summaryLabel.
But what about its Y position and Width and Height?
So we need more constraints.
summaryLabel
Same is applicable for summaryLabel.
So, lets define them properly:
NSDictionary *viewsDictionary =
NSDictionaryOfVariableBindings(nameLabel, summaryLabel);
NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:#"H:|-[nameLabel(100)][summaryLabel]-|" options:0 metrics:nil views:viewsDictionary];
NSArray *constraints1 = [NSLayoutConstraint constraintsWithVisualFormat:#"V:|-[nameLabel(30)]" options:0 metrics:nil views:viewsDictionary];
NSArray *constraints2 = [NSLayoutConstraint constraintsWithVisualFormat:#"V:|-[summaryLabel]" options:0 metrics:nil views:viewsDictionary];
NSArray *constraints3 = [NSLayoutConstraint constraintsWithVisualFormat:#"V:[nameLabel(==summaryLabel)]" options:0 metrics:nil views:viewsDictionary];
[self.view addConstraints:constraints];
[self.view addConstraints:constraints1];
[self.view addConstraints:constraints2];
[self.view addConstraints:constraints3];
Now your views will look fine.
At any point of time, to check if your views are missing any constraints, pause the debugger and type the following in the console
po [[UIWindow keyWindow] _autolayoutTrace]
it will show which of your views are having AMBIGUOUS LAYOUT
Also, remember in Storyboard/IB if the constraints are showing as "orange" colour, you need more constraints to define the objects position. Once you have added all necessary constraints, the constraints colours turn to "blue"
First, are you adding constraints to self.contentView after creation?
Second, maybe your constraint set is insufficient for autolayout and it creates own constraints based on autoresizing mask. Try to add vertical constraints and width constraints for labels.
I made a few UIScrollView's in different views, they all worked without Autolayout.
I turned Autolayout on, because it was better for my app.
But since then, there's a big problem with my UIScrollView's:
No one is scrolling, they don't work.
Here's my code for a UIScrollView:
.m:
-(viewDidLoad) {
scrollerHome.contentSize = CGSizeMake(320, 1000);
scrollerHome.scrollEnabled = YES;
[self.view addSubview:scrollerHome];
scrollerHome.showsHorizontalScrollIndicator = false;
scrollerHome.showsVerticalScrollIndicator = false;
[super viewDidLoad];
}
.h:
#interface ViewController : UIViewController{
IBOutlet UIScrollView *scrollerHome;
}
Do I have to add some code because I turned on Autolayout?
You should call [super viewDidLoad] before doing anything !
In autolayout, you do not set the contentSize manually. Autolayout works slightly differently with scrollviews, whereby the contentSize of the scroll view is dictated by the constraints of the scrollview's subviews.
If you're trying to force the contentSize to some large size (for example, you're implementing some infinite scroller), you can just add a subview of the appropriate size, e.g.:
UIView *containerView = [[UIView alloc] init];
containerView.translatesAutoresizingMaskIntoConstraints = NO;
[self.scrollView addSubview:containerView];
NSDictionary *views = NSDictionaryOfVariableBindings(containerView);
[self.scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[containerView]|" options:0 metrics:nil views:views]];
[self.scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[containerView(1000)]|" options:0 metrics:nil views:views]];
But if you were trying to set the contentSize in anticipation of adding subviews, you generally don't have to do anything, such as the above snippet. Just add your subviews, provide their constraints, and autolayout will adjust the scroll view's contentSize automatically.
As mentioned above, with autolayout, you can just add the subviews to your scrollview (with their constraints), and the contentSize will be calculated automatically for you.
There is a trick here, though. You sometimes you want to size a subview based upon the dimensions of the screen. But the usual technique of using the | symbols won't work. For example, for an imageview1 inside a scrollview, the usual #"H:|[imageview1]|" won't set the imageview1 to be the width of the screen, but rather it will define the scroll view's contentSize to match the width of imageview1, but it says nothing about what the width of that image view should be!
So, it's useful to capture a reference to the scroll view's superview. That way, you can use something like #"H:|[imageview1(==superview)]|", which not only says "make the scroll view's contentSize equal to the width of imageview1", but also "define the width of imageview1 to be equal to the width of the scroll view's superview."
Thus, for example, to add three images in a paging scroll view, you might do something like:
UIImageView *imageview1 = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"_DSC0004.jpg"]];
imageview1.contentMode = UIViewContentModeScaleAspectFit;
imageview1.translatesAutoresizingMaskIntoConstraints = NO;
[self.scrollView addSubview:imageview1];
UIImageView *imageview2 = ... // configured similar to imageview1
UIImageView *imageview3 = ... // configured similar to imageview1
UIView *superview = self.scrollView.superview;
NSDictionary *views = NSDictionaryOfVariableBindings(imageview1, imageview2, imageview3, superview);
// not only define the image view's relation with their immediate scroll view,
// but also explicitly set the size in relation to the superview, too!
[superview addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[imageview1(==superview)][imageview2(==superview)][imageview3(==superview)]|" options:0 metrics:nil views:views]];
[superview addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[imageview1(==superview)]|" options:0 metrics:nil views:views]];
[superview addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[imageview2(==superview)]|" options:0 metrics:nil views:views]];
[superview addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[imageview3(==superview)]|" options:0 metrics:nil views:views]];
self.scrollView.pagingEnabled = YES;
From the Apple iOS 6.0 release notes:
"In general, Auto Layout considers the top, left, bottom, and right edges of a view to be the visible edges. That is, if you pin a view to the left edge of its superview, you’re really pinning it to the minimum x-value of the superview’s bounds. Changing the bounds origin of the superview does not change the position of the view.
The UIScrollView class scrolls its content by changing the origin of its bounds. To make this work with Auto Layout, the top, left, bottom, and right edges within a scroll view now mean the edges of its content view."
You can find the full notes here and find the answer to your question in the section that I quoted from. They give code examples on how to use UIScrollView in a mixed Auto Layout environment.