[英]increase property observer width every time func is called
在我的 swift 代碼中,當我使用 propertyObserver 添加另一個框時,滾動視圖下方的代碼已修復,我無法增加滾動視圖。 每次將新項目添加到計數器時,我希望滾動條的大小增加。 我在下面添加了一個 gif 來顯示問題所在。 您可以看到新空間沒有添加到滾動視圖中。
import UIKit
class PropertyObserverExmple {
var number: Int = 0 {
willSet(newNumber) {
print("About to change to \(newNumber)")
}
didSet(oldNumber) {
print("Just changed from \(oldNumber) to \(self.number)")
}
}
}
var observer = PropertyObserverExmple()
class SwipeableUIScrollView: UIScrollView {
override func touchesShouldCancel(in view: UIView) -> Bool {
if view is UIButton || view is UILabel{
return true
}
return touchesShouldCancel(in: view)
}
}
class ViewController: UIViewController {
var scrollView:SwipeableUIScrollView!
var greenView:UIView!
var addMore:UIButton!
var leadingAnchor: NSLayoutXAxisAnchor!
var counter: Int? {
didSet {
for i in (oldValue ?? 0)..<(counter ?? 0){
let t_button = UIButton.init(frame: CGRect.zero)
t_button.translatesAutoresizingMaskIntoConstraints = false
t_button.backgroundColor = UIColor.blue
scrollView.addSubview(t_button)
NSLayoutConstraint.activate([
t_button.leadingAnchor.constraint(equalTo: leadingAnchor, constant:5.0),
t_button.centerYAnchor.constraint(equalTo: scrollView.centerYAnchor),
t_button.heightAnchor.constraint(equalToConstant: 20),
t_button.widthAnchor.constraint(equalToConstant: 75.0)
])
leadingAnchor = t_button.trailingAnchor
t_button.setTitle("Button \(i)", for: .normal)
}
}
}
var scrollViewHeightConstraint:NSLayoutConstraint!
override func viewDidLoad() {
super.viewDidLoad()
observer.number = 4
scrollView = SwipeableUIScrollView.init(frame: CGRect.zero)
scrollView.translatesAutoresizingMaskIntoConstraints = false
greenView = UIView.init(frame: CGRect.zero)
greenView.translatesAutoresizingMaskIntoConstraints = false
greenView.backgroundColor = UIColor.green
addMore = UIButton.init(frame: CGRect.zero)
addMore.translatesAutoresizingMaskIntoConstraints = false
addMore.backgroundColor = UIColor.orange
addMore.setTitle("add", for: .normal)
self.view.addSubview(scrollView)
self.view.addSubview(greenView)
self.view.addSubview(addMore)
addMore.addTarget(self, action: #selector(increaseC), for: .touchDown)
scrollViewHeightConstraint = NSLayoutConstraint.init(item: scrollView, attribute: .height, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: 50.0)
NSLayoutConstraint.activate([
addMore.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 50.0),
addMore.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: -15.0),
addMore.heightAnchor.constraint(equalToConstant: 25.0),
addMore.widthAnchor.constraint(equalToConstant: 100.0),
scrollView.topAnchor.constraint(equalTo: self.addMore.bottomAnchor, constant: 10.0),
scrollView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor),
scrollView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor),
scrollViewHeightConstraint,
greenView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor),
greenView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor),
greenView.topAnchor.constraint(equalTo: self.scrollView.bottomAnchor),
greenView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor)
])
leadingAnchor = self.scrollView!.leadingAnchor
counter = 10
self.scrollView.trailingAnchor.constraint(equalTo: leadingAnchor).isActive = true
}
@objc func increaseC(){
counter! += 1
}
}
目前還不清楚你想用你的“PropertyObserver”做什么......
但是,有一個更簡單的方法來實現這一點......
UIStackView
作為滾動視圖的子視圖Content Layout Guide
這是一個簡單的例子:
class PropertyObserverExmple {
var number: Int = 0 {
willSet(newNumber) {
print("About to change to \(newNumber)")
}
didSet(oldNumber) {
print("Just changed from \(oldNumber) to \(self.number)")
}
}
}
var observer = PropertyObserverExmple()
class SwipeableUIScrollView: UIScrollView {
override func touchesShouldCancel(in view: UIView) -> Bool {
if view is UIButton || view is UILabel{
return true
}
return touchesShouldCancel(in: view)
}
}
class ScrollButtonsViewController: UIViewController {
// this will hold the buttons
var stackView: UIStackView!
var scrollView:SwipeableUIScrollView!
var greenView:UIView!
var addMore:UIButton!
var leadingAnchor: NSLayoutXAxisAnchor!
var counter: Int? {
didSet {
for i in (oldValue ?? 0)..<(counter ?? 0) {
let t_button = UIButton()
t_button.translatesAutoresizingMaskIntoConstraints = false
t_button.backgroundColor = UIColor.blue
// add it to the stack view, not the scroll view
//scrollView.addSubview(t_button)
stackView.addArrangedSubview(t_button)
NSLayoutConstraint.activate([
t_button.heightAnchor.constraint(equalToConstant: 20),
t_button.widthAnchor.constraint(equalToConstant: 75.0)
])
t_button.setTitle("Button \(i)", for: .normal)
}
}
}
var scrollViewHeightConstraint:NSLayoutConstraint!
override func viewDidLoad() {
super.viewDidLoad()
observer.number = 4
scrollView = SwipeableUIScrollView.init(frame: CGRect.zero)
scrollView.translatesAutoresizingMaskIntoConstraints = false
greenView = UIView.init(frame: CGRect.zero)
greenView.translatesAutoresizingMaskIntoConstraints = false
greenView.backgroundColor = UIColor.green
addMore = UIButton.init(frame: CGRect.zero)
addMore.translatesAutoresizingMaskIntoConstraints = false
addMore.backgroundColor = UIColor.orange
addMore.setTitle("add", for: .normal)
addMore.setTitleColor(.white, for: .normal)
addMore.setTitleColor(.black, for: .highlighted)
self.view.addSubview(scrollView)
self.view.addSubview(greenView)
self.view.addSubview(addMore)
addMore.addTarget(self, action: #selector(increaseC), for: .touchDown)
// respect safe area
let g = view.safeAreaLayoutGuide
scrollViewHeightConstraint = scrollView.heightAnchor.constraint(equalToConstant: 50.0)
NSLayoutConstraint.activate([
addMore.topAnchor.constraint(equalTo: g.topAnchor, constant: 50.0),
addMore.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -15.0),
addMore.heightAnchor.constraint(equalToConstant: 25.0),
addMore.widthAnchor.constraint(equalToConstant: 100.0),
scrollView.topAnchor.constraint(equalTo: self.addMore.bottomAnchor, constant: 10.0),
scrollView.leadingAnchor.constraint(equalTo: g.leadingAnchor),
scrollView.trailingAnchor.constraint(equalTo: g.trailingAnchor),
scrollViewHeightConstraint,
greenView.leadingAnchor.constraint(equalTo: g.leadingAnchor),
greenView.trailingAnchor.constraint(equalTo: g.trailingAnchor),
greenView.topAnchor.constraint(equalTo: self.scrollView.bottomAnchor),
greenView.bottomAnchor.constraint(equalTo: g.bottomAnchor)
])
stackView = UIStackView()
stackView.axis = .horizontal // the default, but just for clarity
stackView.distribution = .fill // the default, but just for clarity
stackView.alignment = .center
stackView.spacing = 5
stackView.translatesAutoresizingMaskIntoConstraints = false
// add the stack view to the scroll view
scrollView.addSubview(stackView)
// constrain the stack view
// this will ALSO define the "scrollable" area
NSLayoutConstraint.activate([
// constrain stack view to scroll view's Content Layout Guide
stackView.topAnchor.constraint(equalTo: scrollView.contentLayoutGuide.topAnchor),
stackView.leadingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.leadingAnchor),
stackView.trailingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.trailingAnchor),
stackView.bottomAnchor.constraint(equalTo: scrollView.contentLayoutGuide.bottomAnchor),
// constrain stack view height to scroll view's Frame Layout Guide
stackView.heightAnchor.constraint(equalTo: scrollView.frameLayoutGuide.heightAnchor),
])
counter = 10
}
@objc func increaseC(){
counter! += 1
}
}
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