修复来自 DatePicker 的数百行警告重新布局约束

Question

在 SwiftUI 中使用新的 (iOS 14) DatePicker，它按预期工作并且在模拟器和设备上看起来很好，但是一旦日历弹出，我会在输出窗口中收到几行警告。这是一个有点讨厌！

虽然日志贴在下面，但看似相关的内容似乎是：

    UIDatePicker 0x7fbd66fc49f0 is being laid out below its minimum width of 280. This may not look like expected, especially with larger than normal font sizes.

但是，正如下面的代码所示，我不限制任何小于 300 点的内容。而且，一切都显示正常。

从我的角度来看，两种解决方案中的任何一种都可以正常工作：

• 禁止所有警告，或
• 向代码添加任何修复以消除警告

弹出日期选择器的代码，一旦点击控件就会生成所有警告：

struct MyCustomDatePicker : View {
    var doSomething : (Date) -> ()
    @State var title: String
    @State var ignoreSelStart : Bool
    @State var ignoreSelEnd : Bool
    @State var selectedDate : Date
    @ObservedObject var limits : DateRangeLimits
     
    var body: some View {
        VStack {
            DatePicker(
                "\(title)", selection: $selectedDate,
                in: ((ignoreSelStart ? limits.hardStart : limits.selectedStart)...(ignoreSelEnd ? limits.hardEnd : limits.selectedEnd)), displayedComponents: [.date]
                )
            .onChange(of: selectedDate, perform: { value in
                doSomething(selectedDate)
            })
        }
        .frame(width: 400, height: 100, alignment: .center)
        .background(Color.white)
    }
}

这struct是从这里调用的：

struct FlexChoice : View {     
    @ObservedObject var limits = DateRangeLimits()

    func setStart(d: Date) {
        // stuff
    }
    func setEnd(d: Date) {
        // stuff
    }
 
    var body: some View {
        VStack(spacing: 0) {
            if customDateRangePossible {
                HStack {
                    MyCustomDatePicker(doSomething: self.setStart, title: "Begin ",
                                    ignoreSelStart: true, ignoreSelEnd: false,
                                    selectedDate: limits.selectedStart, limits: limits)
                    MyCustomDatePicker(doSomething: self.setEnd, title: "Finish ",
                                    ignoreSelStart: false, ignoreSelEnd: true,
                                    selectedDate: limits.selectedEnd, limits: limits)
                }       // closes HStack               
            }       // closes "if customDateRangePossible..."           
        }       // closes VStack
    }       // closes body
}       // closes struct

警告的第一部分：

2021-01-23 10:06:35.707334-0600 MyAppName[28362:46367754] [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. 
(
    "<_UISystemBaselineConstraint:0x6000011979d0 H:[_UIDatePickerLinkedLabel:0x7fbd66ffda10]-(NSLayoutAnchorConstraintSpace(8))-[UILayoutGuide:0x6000008f4540'']   (active)>",
    "<_UISystemBaselineConstraint:0x600001196f30 H:[UILayoutGuide:0x6000008f4540'']-(>=NSLayoutAnchorConstraintSpace(8))-[_UIDatePickerTouchOutsetButton:0x7fbd66f8e9d0]   (active)>",
    "<NSLayoutConstraint:0x600001197070 _UIDatePickerLinkedLabel:0x7fbd66ffda10.leading == UILayoutGuide:0x6000008f41c0'UIViewLayoutMarginsGuide'.leading   (active)>",
    "<NSLayoutConstraint:0x600001194fa0 H:[_UIDatePickerTouchOutsetButton:0x7fbd66f8e9d0]-(28)-[_UIDatePickerTouchOutsetButton:0x7fbd72922e40]   (active)>",
    "<NSLayoutConstraint:0x600001197340 _UIDatePickerTouchOutsetButton:0x7fbd72922e40.trailing == UILayoutGuide:0x6000008f41c0'UIViewLayoutMarginsGuide'.trailing   (active)>",
    "<NSLayoutConstraint:0x6000011975c0 UILayoutGuide:0x6000008f4540''.width == UIImageView:0x7fbd66f8e800.width   (active)>",
    "<NSLayoutConstraint:0x60000125fca0 _UIDatePickerCalendarContentStackView:0x7fbd66f8ad40.width <= _UIDatePickerCalendarView:0x7fbd66fc49f0.width   (active)>",
    "<NSLayoutConstraint:0x6000011c2f30 H:|-(0)-[_UIDatePickerCalendarView:0x7fbd66fc49f0]   (active, names: '|':UIDatePicker:0x7fbd7298e840 )>",
    "<NSLayoutConstraint:0x6000011c0500 _UIDatePickerCalendarView:0x7fbd66fc49f0.trailing == UIDatePicker:0x7fbd7298e840.trailing   (active)>",
    "<NSLayoutConstraint:0x60000125ee90 H:|-(8)-[UIDatePicker:0x7fbd7298e840]   (active, names: '|':UIView:0x7fbd72d46870 )>",
    "<NSLayoutConstraint:0x6000012573e0 UIDatePicker:0x7fbd7298e840.trailing == UIView:0x7fbd72d46870.trailing - 8   (active)>",
    "<NSLayoutConstraint:0x6000011de120 'UISV-canvas-connection' _UIDatePickerCalendarContentStackView:0x7fbd66f8ad40.leading == _UIDatePickerCalendarHeaderView:0x7fbd66f8aed0.leading   (active)>",
    "<NSLayoutConstraint:0x6000011df390 'UISV-canvas-connection' H:[_UIDatePickerCalendarHeaderView:0x7fbd66f8aed0]-(0)-|   (active, names: '|':_UIDatePickerCalendarContentStackView:0x7fbd66f8ad40 )>",
    "<NSLayoutConstraint:0x6000011cfca0 'UIView-Encapsulated-Layout-Width' UIView:0x7fbd72d46870.width == 0   (active)>",
    "<NSLayoutConstraint:0x60000119cd20 'UIView-leftMargin-guide-constraint' H:|-(8)-[UILayoutGuide:0x6000008f41c0'UIViewLayoutMarginsGuide'](LTR)   (active, names: '|':_UIDatePickerCalendarHeaderView:0x7fbd66f8aed0 )>",
    "<NSLayoutConstraint:0x6000011977a0 'UIView-rightMargin-guide-constraint' H:[UILayoutGuide:0x6000008f41c0'UIViewLayoutMarginsGuide']-(8)-|(LTR)   (active, names: '|':_UIDatePickerCalendarHeaderView:0x7fbd66f8aed0 )>"
)

Will attempt to recover by breaking constraint 
<_UISystemBaselineConstraint:0x600001196f30 H:[UILayoutGuide:0x6000008f4540'']-(>=NSLayoutAnchorConstraintSpace(8))-[_UIDatePickerTouchOutsetButton:0x7fbd66f8e9d0]   (active)>

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.

接下来是多次重复基本相同的警告（减去在每次连续迭代中刚刚打破的约束）。

在数百行警告的最后是以下内容：

2021-01-23 10:06:35.734386-0600 MyAppName[28362:46367754] [DatePicker] UIDatePicker 0x7fbd66fc49f0 is being laid out below its minimum width of 280. This may not look like expected, especially with larger than normal font sizes.
2021-01-23 10:06:35.740477-0600 MyAppName[28362:46367754] [DatePicker] UIDatePicker 0x7fbd66fc49f0 is being laid out below its minimum width of 280. This may not look like expected, especially with larger than normal font sizes.
2021-01-23 10:06:35.752360-0600 MyAppName[28362:46367754] [DatePicker] UIDatePicker 0x7fbd66fc49f0 is being laid out below its minimum width of 280. This may not look like expected, especially with larger than normal font sizes.

有没有办法让 DatePicker 开心并使它不让这些警告充斥输出窗口，无论是通过修复事物还是抑制警告？

Answer 1

如果您使用 GraphicalDatePickerStyle，请尝试：

DatePicker("", ....)
   .datePickerStyle(GraphicalDatePickerStyle())
   .padding()  // this line solves the problem.

我使用 CompactDatePickerStyle ，不幸的是问题仍然存在。