无法同时满足约束 iOS
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【中文标题】无法同时满足约束 iOS【英文标题】:Unable to simultaneously satisfy constraints iOS 【发布时间】:2020-04-01 16:46:37 【问题描述】:我有一个限制在视图底部的按钮。 该按钮最初是隐藏的,直到点击表格视图中的项目。 表格有一个搜索控制器,当点击它时,我希望使按钮移动,使其始终位于键盘上方。
@objc func keyboardWillShow(notification: NSNotification)
if let keyboardHeight = (notification.userInfo?[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue.height
startAssessmentBtn.snp.makeConstraints make in
make.bottom.equalTo(-keyboardHeight)
let userInfo = notification.userInfo! as [AnyHashable: Any]
let animationDuration = userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as! NSNumber
let animationCurve = userInfo[UIResponder.keyboardAnimationCurveUserInfoKey] as! NSNumber
UIView.setAnimationCurve(UIView.AnimationCurve(rawValue: animationCurve.intValue)!)
UIView.animate(withDuration: animationDuration.doubleValue)
self.tableView.setBottomInset(to: keyboardHeight)
self.view.layoutIfNeeded()
@objc func keyboardDidHide(notification: NSNotification)
if let keyboardHeight = (notification.userInfo?[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue
let userInfo = notification.userInfo! as [AnyHashable: Any]
let animationDuration = userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as! NSNumber
let animationCurve = userInfo[UIResponder.keyboardAnimationCurveUserInfoKey] as! NSNumber
startAssessmentBtn.snp.makeConstraints make in
make.bottom.equalTo(0)
//make.bottom.equalToSuperview()//.offset(+keyboardHeight)
UIView.setAnimationCurve(UIView.AnimationCurve(rawValue: animationCurve.intValue)!)
UIView.animate(withDuration: animationDuration.doubleValue)
self.tableView.setBottomInset(to: 0.0)
self.startAssessmentBtn.setNeedsLayout()
self.startAssessmentBtn.layoutIfNeeded()
self.view.layoutIfNeeded()
使用上面的代码,我可以在第一次打开键盘时让按钮出现在键盘上方。但是当键盘关闭时,按钮不会返回到屏幕底部。我收到以下约束错误:
2020-04-01 17:38:42.629598+0100 AuditComply 2.0[4550:3372130] [LayoutConstraints] 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.
(
"<SnapKit.LayoutConstraint:0x2830057a0@AssetTreeViewController.swift#126 UIButton:0x121deacd0.bottom == UIView:0x121deb100.bottom - 320.0>",
"<SnapKit.LayoutConstraint:0x283005620@AssetTreeViewController.swift#149 UIButton:0x121deacd0.bottom == UIView:0x121deb100.bottom>"
)
Will attempt to recover by breaking constraint
<SnapKit.LayoutConstraint:0x283005620@AssetTreeViewController.swift#149 UIButton:0x121deacd0.bottom == UIView:0x121deb100.bottom>
Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKitCore/UIView.h> may also be helpful.
因此,keyboardWillShow 的约束似乎覆盖了keyboardDidHide 的约束。我已经尝试更改约束的优先级,但这也不起作用。
【问题讨论】:
在你分配新的约束之前,你应该删除它之前的。 【参考方案1】:很明显,您正在使用 SnapKit。 makeConstraints
为现有约束添加约束。
要更新现有约束,您应该使用updateConstraints
,但您应该锚定到同一点,
例如:.equalToSuperview().inset(0)
和 .equalToSuperview().inset(keyboardHeight)
如果没有锚定到同一点的选项,您应该清除以前的约束并创建一些新的约束。您可以使用 .remakeConstraints
同时执行此操作,但您应该添加所有其他约束,例如前导、尾随、顶部
【讨论】:
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