全新SwiftUI项目中TextField触发[LayoutConstraints]错误的解决办法

我创建了一个全新的纯SwiftUI项目，未添加任何自定义样式，仅实现了包含TextField和SecureField的基础视图：

struct ContentView: View {
    @State private var email = ""
    @State private var password = ""
    
    var body: some View {
        VStack {
            TextField("Email", text: $email)
            SecureField("Password", text: $password)
        }
    }
}

运行后出现了布局约束冲突警告：

2023-04-27 09:43:13.444617+0400 Test[16580:1186362] [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. 
(
    "<NSLayoutConstraint:0x282228320 'accessoryView.bottom' _UIRemoteKeyboardPlaceholderView:0x11d1105c0.bottom == _UIKBCompatInputView:0x11be0f3b0.top   (active)>",
    "<NSLayoutConstraint:0x282229900 'assistantHeight' SystemInputAssistantView.height == 45   (active, names: SystemInputAssistantView:0x11d205d00 )>",
    "<NSLayoutConstraint:0x2822216d0 'assistantView.bottom' SystemInputAssistantView.bottom == _UIKBCompatInputView:0x11be0f3b0.top   (active, names: SystemInputAssistantView:0x11d205d00 )>",
    "<NSLayoutConstraint:0x282221680 'assistantView.top' V:[_UIRemoteKeyboardPlaceholderView:0x11d1105c0]-(0)-[SystemInputAssistantView]   (active, names: SystemInputAssistantView:0x11d205d00 )>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x282221680 'assistantView.top' V:[_UIRemoteKeyboardPlaceholderView:0x11d1105c0]-(0)-[SystemInputAssistantView]   (active, names: SystemInputAssistantView:0x11d205d00 )>

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.

尽管功能不受影响，但希望彻底消除该警告。

方法1：为容器添加内边距或明确布局 #

给VStack添加内边距并设置最小高度，让视图拥有足够的布局空间，避免键盘弹出时的约束挤压：

struct ContentView: View {
    @State private var email = ""
    @State private var password = ""
    
    var body: some View {
        VStack {
            TextField("Email", text: $email)
            SecureField("Password", text: $password)
        }
        .padding()
        .frame(minHeight: UIScreen.main.bounds.height)
    }
}

方法2：用ScrollView包裹输入视图 #

ScrollView会在键盘弹出时自动调整内容布局，从根本上避免约束冲突：

struct ContentView: View {
    @State private var email = ""
    @State private var password = ""
    
    var body: some View {
        ScrollView {
            VStack {
                TextField("Email", text: $email)
                SecureField("Password", text: $password)
            }
            .padding()
        }
    }
}

方法3：升级Xcode/iOS版本 #

该警告大概率是特定iOS版本（如iOS 16.x早期版本）的系统bug，升级到最新的Xcode和iOS版本通常能解决这类底层布局问题。

方法4：禁用键盘辅助视图（极端方案） #

如果上述方法无效，可以通过UIKit扩展禁用键盘的辅助输入栏（换行、表情按钮等），从根源上消除相关约束：

extension UITextField {
    override open func didMoveToWindow() {
        super.didMoveToWindow()
        inputAssistantItem.trailingBarButtonGroups = []
        inputAssistantItem.leadingBarButtonGroups = []
    }
}

extension UITextView {
    override open func didMoveToWindow() {
        super.didMoveToWindow()
        inputAssistantItem.trailingBarButtonGroups = []
        inputAssistantItem.leadingBarButtonGroups = []
    }
}

内容的提问来源于stack exchange，提问作者Pro Girl