修复输入动画边框被裁剪问题

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

LearnEnglish/LearnEnglish/Views/SpellingInputView.swift

@@ -5,6 +5,7 @@ final class SpellingInputView: UIView, UITextFieldDelegate {
 
     private let hiddenField = UITextField()
     private let stack = UIStackView()
+    private let scrollView = UIScrollView()
 
     private var chars: [String] = []
     private var blankPositions: [Int] = []
@@ -20,18 +21,31 @@ final class SpellingInputView: UIView, UITextFieldDelegate {
 
     override init(frame: CGRect) {
         super.init(frame: frame)
+
+        scrollView.showsHorizontalScrollIndicator = false
+        scrollView.showsVerticalScrollIndicator = false
+        scrollView.clipsToBounds = false
+        addSubview(scrollView)
+        scrollView.translatesAutoresizingMaskIntoConstraints = false
+        NSLayoutConstraint.activate([
+            scrollView.topAnchor.constraint(equalTo: topAnchor),
+            scrollView.bottomAnchor.constraint(equalTo: bottomAnchor),
+            scrollView.leadingAnchor.constraint(equalTo: leadingAnchor),
+            scrollView.trailingAnchor.constraint(equalTo: trailingAnchor)
+        ])
+
         stack.axis = .horizontal
         stack.spacing = 6
         stack.alignment = .center
         stack.isUserInteractionEnabled = true
-        addSubview(stack)
+        scrollView.addSubview(stack)
         stack.translatesAutoresizingMaskIntoConstraints = false
         NSLayoutConstraint.activate([
-            stack.topAnchor.constraint(equalTo: topAnchor),
-            stack.bottomAnchor.constraint(equalTo: bottomAnchor),
-            stack.centerXAnchor.constraint(equalTo: centerXAnchor),
-            stack.leadingAnchor.constraint(greaterThanOrEqualTo: leadingAnchor),
-            stack.trailingAnchor.constraint(lessThanOrEqualTo: trailingAnchor)
+            stack.topAnchor.constraint(equalTo: scrollView.contentLayoutGuide.topAnchor),
+            stack.bottomAnchor.constraint(equalTo: scrollView.contentLayoutGuide.bottomAnchor),
+            stack.leadingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.leadingAnchor),
+            stack.trailingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.trailingAnchor),
+            stack.heightAnchor.constraint(equalTo: scrollView.frameLayoutGuide.heightAnchor)
         ])
 
         hiddenField.delegate = self
@@ -126,17 +140,9 @@ final class SpellingInputView: UIView, UITextFieldDelegate {
 
     private func rebuildBoxes() {
         stack.arrangedSubviews.forEach { $0.removeFromSuperview() }
-        let count = CGFloat(max(chars.count, 1))
-        let available = (window?.screen.bounds.width ?? 390) - 32
-        var spacing: CGFloat = 6
-        var boxWidth = (available - spacing * (count - 1)) / count
-        if boxWidth < 16 {
-            spacing = 3
-            boxWidth = (available - spacing * (count - 1)) / count
-        }
-        boxWidth = min(36, boxWidth)
-        stack.spacing = spacing
-        let fontSize = min(22, max(12, boxWidth * 0.62))
+        let boxWidth: CGFloat = 32
+        let fontSize: CGFloat = 20
+        stack.spacing = 6
         boxViews = chars.enumerated().map { index, ch in
             let box = makeBox(fontSize: fontSize)
             box.tag = index
@@ -153,6 +159,22 @@ final class SpellingInputView: UIView, UITextFieldDelegate {
             return box
         }
         refreshBoxes()
+        DispatchQueue.main.async { [weak self] in
+            self?.updateAlignment()
+        }
+    }
+
+    private func updateAlignment() {
+        let totalWidth = CGFloat(chars.count) * 32 + CGFloat(max(chars.count - 1, 0)) * 6
+        let available = scrollView.bounds.width
+        if totalWidth <= available {
+            let inset = max(0, (available - totalWidth) / 2)
+            scrollView.contentInset = UIEdgeInsets(top: 0, left: inset, bottom: 0, right: inset)
+            scrollView.isScrollEnabled = false
+        } else {
+            scrollView.contentInset = .zero
+            scrollView.isScrollEnabled = true
+        }
     }
 
     @objc private func boxTapped(_ gesture: UITapGestureRecognizer) {