ios 以编程方式更新高度约束
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Update height constraint programmatically
提问by Tapas Pal
I am new in auto layout. I have done all of my project from xib file, but now I faced a problem where I have to update an view's height programmatically. I have tried below but now working.
我是自动布局的新手。我已经从 xib 文件完成了我的所有项目，但现在我遇到了一个问题，我必须以编程方式更新视图的高度。我在下面尝试过，但现在正在工作。
[[self view] addConstraint:[NSLayoutConstraint constraintWithItem:loginContainer attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0f constant:loginFrame.size.height]];
In console it's shows
在控制台中显示
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)
(
"<NSLayoutConstraint:0x78724530 V:[UIView:0x790cdfb0(170)]>",
"<NSLayoutConstraint:0x787da210 V:[UIView:0x790cdfb0(400)]>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x78724530 V:[UIView:0x790cdfb0(170)]>
Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
回答by Dave Paul
Instead of adding a new constraint, you need to modify the constant on your existing constraint.
您需要修改现有约束上的常量，而不是添加新约束。
Use an IBOutlet to connect to your constraint in Interface Builder:
使用 IBOutlet 连接到 Interface Builder 中的约束：
@property (nonatomic, weak) NSLayoutConstraint *heightConstraint;
Then, when you need to set it programmatically, simply set the constant property on the constraint:
然后，当您需要以编程方式设置它时，只需在约束上设置常量属性：
heightConstraint.constant = 100;
OR
或者
If you can't access the nib in Interface Builder, find the constraint in code:
如果在 Interface Builder 中无法访问笔尖，请在代码中找到约束：
NSLayoutConstraint *heightConstraint;
for (NSLayoutConstraint *constraint in myView.constraints) {
if (constraint.firstAttribute == NSLayoutAttributeHeight) {
heightConstraint = constraint;
break;
}
}
heightConstraint.constant = 100;
And in Swift:
在 Swift 中：
if let constraint = (myView.constraints.filter{self.heightConstraint.constant = 300;
[self.view updateConstraints];
.firstAttribute == .width}.first) {
constraint.constant = 100.0
}
回答by Hamza
To get a reference of your height constraints : Click + Ctrl in the constraint and drag and drop in your class file :
要获取高度约束的参考：在约束中单击 + Ctrl 并拖放到类文件中：
To update constraint value :
更新约束值：
extension UIView {
func updateConstraint(attribute: NSLayoutAttribute, constant: CGFloat) -> Void {
if let constraint = (self.constraints.filter{// to update height constant
testView.updateConstraint(attribute: NSLayoutAttribute.height, constant: 20.0)
// to update width constant
testView.updateConstraint(attribute: NSLayoutAttribute.width, constant: 20.0)
.firstAttribute == attribute}.first) {
constraint.constant = constant
self.layoutIfNeeded()
}
}
}
回答by Krunal
A more flexible way using this swift extension:
使用此 swift 扩展的更灵活的方法：
[[NSBundle mainBundle] loadNibNamed:@"NibView" owner:self options:nil];
How to use this view extension to update constant value of existing constraints:
如何使用此视图扩展更新现有约束的常量值：
nibView.translatesAutoresizingMaskIntoConstraints = NO;
回答by fdiaz
Let's call your view nibView. So, you are trying to load that view in a view controller, so first, in your view controller, you need to load it as you are doing it with:
让我们将您的视图称为nibView。因此，您正在尝试在视图控制器中加载该视图，因此首先，在您的视图控制器中，您需要按照以下方式加载它：
NSLayoutConstraint *heightConstraint = [NSLayoutConstraint constraintWithItem:nibView
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:nil
attribute:NSLayoutAttributeNotAnAttribute
multiplier:1.0
constant:yourValue];
Then you need to tell the nibView that you don't need it to transform the autoresizing masks into constraints by doing
然后你需要告诉 nibView 你不需要它通过执行将自动调整大小掩码转换为约束
[self.view addConstraint:heightConstraint];
Then, you can add your constraints
然后，您可以添加约束
import UIKit
class AnimateHeightConstraintViewController: UIViewController {
var flowHeightConstraint: NSLayoutConstraint?
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .white
view.addSubview(button)
button.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
button.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
button.widthAnchor.constraint(equalToConstant: 100).isActive = true
flowHeightConstraint = button.heightAnchor.constraint(equalToConstant: 30)
flowHeightConstraint?.isActive = true
}
@objc func animateButtonTapped() {
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.5, initialSpringVelocity: 0.5, options: .curveEaseOut, animations: {
self.flowHeightConstraint?.constant = 100
self.view.layoutIfNeeded()
}, completion: nil)
}
lazy var button: UIButton = {
let button = UIButton()
button.translatesAutoresizingMaskIntoConstraints = false
button.backgroundColor = .green
button.addTarget(self, action: #selector(animateButtonTapped), for: .touchUpInside)
return button
}()
}
And finally just add it to your view constraints:
最后将其添加到您的视图约束中：
##代码##You probably would need to add a width constraint also.
您可能还需要添加宽度约束。
回答by moraei
Swift 4.2
斯威夫特 4.2
Using auto layout and animation to increase height of button
使用自动布局和动画来增加按钮的高度
I don't use story board. all things in code.
我不使用故事板。代码中的所有内容。
##代码##and result is like this:
结果是这样的：
