SwiftUI中使用NSTextView时Find bar无法显示问题求助

核心原因 #

SwiftUI环境下NSTextView的Find Bar无法显示，主要源于视图生命周期时机不匹配和第一响应者设置无效：

• Window关联时机过早：在makeNSView方法中调用textView.window?.makeFirstResponder(textView)时，textView尚未被SwiftUI添加到窗口的视图层级，textView.window为nil，导致第一响应者设置失败。而Find Bar的激活依赖textView成为第一响应者且已关联到窗口。
• Find Bar初始化逻辑未触发：NSTextView的Find Bar由其所在的NSScrollView托管，只有当textView成为第一响应者、窗口存在且usesFindBar/usesFindPanel属性正确设置时，系统才会初始化并显示Find Bar。SwiftUI的视图挂载延迟导致这些条件在初始化阶段未满足，后续也未自动触发检查。
• 菜单命令关联缺失：SwiftUI默认未绑定Find相关的菜单快捷键（如Cmd+F），即使textView准备就绪，也无法通过常规操作唤起Find Bar。

解决方法 #

1. 延迟设置第一响应者 #

将第一响应者的设置延迟到textView被添加到窗口后执行，可通过以下两种方式实现：

方法一：使用延迟异步任务修改makeNSView

func makeNSView(context: Context) -> NSScrollView {
    let scrollView = NSTextView.scrollableTextView()
    guard let textView = scrollView.documentView as? NSTextView else {
        return scrollView
    }
    // 保留原有属性设置
    textView.allowsUndo = true
    textView.usesFindBar = true
    textView.usesFindPanel = false
    textView.isIncrementalSearchingEnabled = true
    textView.isContinuousSpellCheckingEnabled = true
    textView.font = NSFont.monospacedSystemFont(ofSize: 15, weight: .regular)
    textView.textColor = NSColor(Color.onSurface)
    
    // 延迟设置第一响应者，确保textView已挂载到窗口
    DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
        textView.window?.makeFirstResponder(textView)
    }
    
    DispatchQueue.main.async {
        textView.string = text
        textView.delegate = context.coordinator
    }
    return scrollView
}

方法二：监听视图移动到窗口的通知

在Coordinator中添加监听，确保textView进入窗口后立即成为第一响应者：

class Coordinator: NSObject, NSTextViewDelegate {
    var parent: TextView
    
    init(_ parent: TextView) {
        self.parent = parent
        super.init()
        // 监听视图移动到窗口的通知
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(textViewDidMoveToWindow(_:)),
            name: NSView.didMoveToWindowNotification,
            object: nil
        )
    }
    
    @objc private func textViewDidMoveToWindow(_ notification: Notification) {
        guard let textView = notification.object as? NSTextView else { return }
        textView.window?.makeFirstResponder(textView)
    }
    
    // 保留原有代理方法
    func textDidEndEditing(_ notification: Notification) {
        guard let textView = notification.object as? NSTextView else { return }
        parent.text = textView.string
        textView.undoManager?.removeAllActions()
    }
    
    func textDidChange(_ notification: Notification) {
        guard let textView = notification.object as? NSTextView else { return }
        let string = textView.string
        let length = string.count
        let insertionPoint = textView.selectedRange.location
        let low = max(0, insertionPoint - 1)

        if let range = Range(NSRange(location: low, length: 1), in: string) {
            let newChar = string[range]

            if length > 0 && length > parent.text.count, newChar == "\n" {
                parent.text = textView.string
                parent.onAddingNewLine?()
            } else {
                parent.text = textView.string
            }
        } else {
            parent.text = textView.string
        }
    }

    func textViewDidChangeSelection(_ notification: Notification) {
        guard let textView = notification.object as? NSTextView else { return }
        parent.selectedRange = textView.selectedRange
    }
}

2. 绑定Find菜单快捷键 #

在SwiftUI的App结构体中添加Find命令的快捷键绑定，确保用户可通过Cmd+F唤起Find Bar：

@main
struct YourApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
        .commands {
            CommandGroup(replacing: .find) {
                Button("Find") {
                    NSApp.keyWindow?.firstResponder?.showFindBar(nil)
                }
                .keyboardShortcut("f", modifiers: .command)
                
                Button("Find Next") {
                    NSApp.keyWindow?.firstResponder?.performSelector(onMainThread: #selector(NSTextView.findNext(_:)), with: nil, waitUntilDone: false)
                }
                .keyboardShortcut("g", modifiers: .command)
                
                Button("Find Previous") {
                    NSApp.keyWindow?.firstResponder?.performSelector(onMainThread: #selector(NSTextView.findPrevious(_:)), with: nil, waitUntilDone: false)
                }
                .keyboardShortcut("g", modifiers: [.command, .shift])
            }
        }
    }
}

3. 手动触发Find Bar（可选） #

若需要主动触发Find Bar显示，可在合适时机调用textView的showFindBar(_:)方法：

// 示例：在按钮点击事件中触发
textView.showFindBar(nil)

内容的提问来源于stack exchange，提问作者rizwana desai