我有一个自定义 UIView,我使用此函数在 View Controller 中实例化它,displayTimer 是 View Controller 的 iVar:
func changeViewModeTo(mode: String){
if mode == "settings" {
addSettingsModeConstraints()
animatedLayoutIfNeeded(removeView: true)
}
if mode == "timer" {
displayedTimer = TimerView.init()
displayedTimer.frame = CGRect(x: (self.view.bounds.size.width)/2 - 50, y: (self.view.bounds.size.height)/2 - 80, width: 100, height: 160)
let colors = timer.getColorScheme()
displayedTimer.setColorScheme(colorLight: colors["lightColor"]!, colorDark: colors["darkColor"]!)
displayedTimer.setTimeRemainingLabel(timer.duration)
displayedTimer.setCountDownBarFromPercentage(1.0)
displayedTimer.layer.zPosition = 100 //make sure the timer view sits on top of the settings panel
displayedTimer.timerLabel.hidden = false
displayedTimer.translatesAutoresizingMaskIntoConstraints = false
let pinchGestureRecogniser = UIPinchGestureRecognizer(target: self, action: #selector(self.pinchDetected(_:)))
displayedTimer.addGestureRecognizer(pinchGestureRecogniser)
self.view.addSubview(displayedTimer)
addTimerModeConstraints()
animatedLayoutIfNeeded(removeView: false)
}
}
如果模式设置为计时器,那么它会创建 UIView 的子类并为其设置实例变量,添加约束以使其全屏,然后调用动画的layoutIfNeeded()。如果设置的模式是settings,那么它会停用timerConstraints,添加新的约束来缩小 View ,调用动画layoutIfNeeded,然后从superView中删除 View 。
func animatedLayoutIfNeeded(removeView removeView: Bool){
UIView.animateWithDuration(0.2, delay: 0, options: [UIViewAnimationOptions.CurveEaseIn] , animations: {
self.view.layoutIfNeeded()
}) { (true) in
if removeView == true {
self.displayedTimer.removeFromSuperview()
}
}
}
使用这些方法添加和删除约束(settingsConstraints和timerConstraints是 View Controller 的iVar):
//MARK: - Layout Constraints
func addSettingsModeConstraints() {
let views = ["timerView": displayedTimer]
let timerHorizontalConstraints = NSLayoutConstraint.constraintsWithVisualFormat(
"H:|-75-[timerView]-75-|",
options: [],
metrics: nil,
views: views)
settingsConstraints += timerHorizontalConstraints
let timerVerticalConstraints = NSLayoutConstraint.constraintsWithVisualFormat(
"V:|-105-[timerView]-85-|",
options: [],
metrics: nil,
views: views)
settingsConstraints += timerVerticalConstraints
NSLayoutConstraint.deactivateConstraints(timerConstraints)
NSLayoutConstraint.activateConstraints(settingsConstraints)
}
func addTimerModeConstraints() {
let views = ["timerView": displayedTimer]
let timerHorizontalConstraints = NSLayoutConstraint.constraintsWithVisualFormat(
"H:|-0-[timerView]-0-|",
options: [],
metrics: nil,
views: views)
timerConstraints += timerHorizontalConstraints
let timerVerticalConstraints = NSLayoutConstraint.constraintsWithVisualFormat(
"V:|-0-[timerView]-0-|",
options: [],
metrics: nil,
views: views)
timerConstraints += timerVerticalConstraints
NSLayoutConstraint.activateConstraints(timerConstraints)
}
changeViewModeTo 从捏合手势识别器调用(负捏合设置一种模式,正捏合设置另一种模式)。
我第一次捏合时, View 就会创建并全屏显示。然后我反向捏合, View 就会缩小并被删除。然后,当我再次捏捏以启动应用程序崩溃的过程时,没有控制台错误,但代码行上有红色错误: NSLayoutConstraint.activateConstraints(timerConstraints)
我猜测删除 subview 会导致对 NSConstraints 的引用消失?
任何想法都会很棒,因为我无法弄清楚。
最佳答案
事实证明这是一个简单的修复,在重新创建和激活它们之前对 settingsConstraints
和 timerConstraints
调用 removeAll()
即可解决问题.
关于ios - 第二次加载 UIView 后 NSConstraints 使应用程序崩溃,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38640782/