fix(player): 固定评论输入浮层位置避免收键盘跳动

lib/pages/player/widgets/comment_composer_sheet.dart

@@ -20,6 +20,8 @@ const double _sheetRadius = 20;
 const double _inputRadius = 12;
 const double _postButtonHeight = 32;
 const int _maxCommentLength = 300;
+const Duration _keyboardSettleDelay = Duration(milliseconds: 80);
+const double _maxKeyboardInsetRatio = 0.6;
 
 /// 独立评论输入弹窗，复用原评论控制器的发布与列表更新能力。
 class CommentComposerSheet extends StatefulWidget {
@@ -44,11 +46,13 @@ class _CommentComposerSheetState extends State<CommentComposerSheet> {
   final _input = TextEditingController();
   final _inputFocus = FocusNode();
   final _keyboardInset = KeyboardInsetNotifier.instance;
+  Timer? _keyboardSettleTimer;
   double _pinnedKeyboardInset = 0;
   int _insetBaseline = 0;
   bool _pinnedInitialized = false;
   bool _insetReady = false;
   bool _useChannelInset = false;
+  bool _keyboardVisible = false;
 
   @override
   void initState() {
@@ -62,9 +66,12 @@ class _CommentComposerSheetState extends State<CommentComposerSheet> {
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
-    if (_pinnedInitialized) return;
-    _pinnedInitialized = true;
-    _pinnedKeyboardInset = MediaQuery.viewInsetsOf(context).bottom;
+    if (!_pinnedInitialized) {
+      _pinnedInitialized = true;
+      _pinnedKeyboardInset =
+          _normalizeKeyboardInset(MediaQuery.viewInsetsOf(context).bottom) ?? 0;
+    }
+    _trackKeyboardInset(_keyboardHeight(context));
   }
 
   Future<void> _prepareInput() async {
@@ -89,6 +96,7 @@ class _CommentComposerSheetState extends State<CommentComposerSheet> {
     _input.removeListener(_onInputChanged);
     _keyboardInset.removeListener(_onKeyboardInsetChanged);
     widget.controller.removeListener(_onControllerChanged);
+    _keyboardSettleTimer?.cancel();
     _inputFocus.unfocus();
     _input.dispose();
     _inputFocus.dispose();
@@ -108,7 +116,7 @@ class _CommentComposerSheetState extends State<CommentComposerSheet> {
     if (_keyboardInset.value != _insetBaseline) {
       _useChannelInset = true;
     }
-    setState(() {});
+    _trackKeyboardInset(_keyboardHeight(context));
   }
 
   double _keyboardHeight(BuildContext context) {
@@ -119,6 +127,38 @@ class _CommentComposerSheetState extends State<CommentComposerSheet> {
     return math.max(viewInset, channelInset);
   }
 
+  double? _normalizeKeyboardInset(double inset) {
+    final maxInset = MediaQuery.sizeOf(context).height * _maxKeyboardInsetRatio;
+    if (!inset.isFinite || inset > maxInset) return null;
+    return math.max(0, inset).roundToDouble();
+  }
+
+  void _trackKeyboardInset(double inset) {
+    final visible = inset > 0;
+    if (visible == _keyboardVisible) return;
+    _keyboardVisible = visible;
+    _keyboardSettleTimer?.cancel();
+    _keyboardSettleTimer = null;
+    if (!visible) return;
+    _keyboardSettleTimer = Timer(
+      _keyboardSettleDelay,
+      _captureSettledKeyboardInset,
+    );
+  }
+
+  void _captureSettledKeyboardInset() {
+    _keyboardSettleTimer = null;
+    if (!mounted) return;
+    final inset = _keyboardHeight(context);
+    if (inset <= 0) {
+      _keyboardVisible = false;
+      return;
+    }
+    final next = _normalizeKeyboardInset(inset);
+    if (next == null || next == _pinnedKeyboardInset) return;
+    setState(() => _pinnedKeyboardInset = next);
+  }
+
   Future<void> _submit() async {
     if (widget.controller.submitting) return;
     final text = _input.text.trim();
@@ -148,8 +188,6 @@ class _CommentComposerSheetState extends State<CommentComposerSheet> {
 
   @override
   Widget build(BuildContext context) {
-    final currentKeyboardInset = _keyboardHeight(context);
-    _pinnedKeyboardInset = math.max(_pinnedKeyboardInset, currentKeyboardInset);
     final l10n = AppLocalizations.of(context)!;
     final signedIn = context.watch<AuthController>().isSignedIn;
     final hasContent = _input.text.trim().isNotEmpty;