fix: 返回时停止备份和日志操作准备

lib/pages/backup_page.dart

@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'dart:typed_data';
 
 import 'package:file_picker/file_picker.dart';
@@ -26,9 +27,18 @@ class BackupPage extends StatefulWidget {
 
 class _BackupPageState extends State<BackupPage> {
   late final ConfigArchive _archive = widget.runtime.backupArchive;
+  Completer<void>? _cancelled;
+  StreamIterator<Uint8List>? _importStream;
   bool _includeAccount = false;
   bool _busy = false;
   bool _waitingForReload = false;
+  bool get _operationActive {
+    AppLog.instance.trace(
+      "lib/pages/backup_page.dart::_BackupPageState._operationActive.get",
+    );
+    return mounted && _cancelled?.isCompleted == false;
+  }
+
   String? _message;
   String? get _statusMessage {
     AppLog.instance.trace(
@@ -39,6 +49,31 @@ class _BackupPageState extends State<BackupPage> {
         : _message;
   }
 
+  @override
+  void dispose() {
+    AppLog.instance.trace(
+      "lib/pages/backup_page.dart::_BackupPageState.dispose",
+    );
+    _cancelOperation();
+    super.dispose();
+  }
+
+  void _cancelOperation() {
+    AppLog.instance.trace(
+      "lib/pages/backup_page.dart::_BackupPageState._cancelOperation",
+    );
+    final cancelled = _cancelled;
+    if (cancelled != null && !cancelled.isCompleted) cancelled.complete();
+    // Provider cleanup errors cannot be shown after leaving the page.
+    unawaited(
+      _importStream?.cancel().catchError((_) {
+        AppLog.instance.trace(
+          "lib/pages/backup_page.dart::_BackupPageState._cancelOperation.closure#1",
+        );
+      }),
+    );
+  }
+
   Future<bool> _confirm(String title, Widget content, String action) {
     AppLog.instance.trace(
       "lib/pages/backup_page.dart::_BackupPageState._confirm",
@@ -59,6 +94,7 @@ class _BackupPageState extends State<BackupPage> {
       );
 
       if (_busy || !mounted) return;
+      final cancelled = _cancelled = Completer<void>();
       setState(() {
         AppLog.instance.trace(
           "lib/pages/backup_page.dart::_BackupPageState._run.closure#1.closure#1",
@@ -71,6 +107,7 @@ class _BackupPageState extends State<BackupPage> {
       try {
         await action();
       } catch (error, stack) {
+        if (cancelled.isCompleted) return;
         final expected =
             error is ConfigArchiveException ||
             error is FormatException ||
@@ -126,6 +163,8 @@ class _BackupPageState extends State<BackupPage> {
           };
         });
       } finally {
+        if (!cancelled.isCompleted) cancelled.complete();
+        _cancelled = null;
         if (mounted)
           setState(() {
             AppLog.instance.trace(
@@ -154,17 +193,20 @@ class _BackupPageState extends State<BackupPage> {
             '仍要导出',
           ))
         return;
-      if (!mounted) return;
-      final bytes = await _archive.export(includeAccount: includeAccount);
-      if (!mounted) return;
+      if (!_operationActive) return;
+      final bytes = await _archive.export(
+        includeAccount: includeAccount,
+        cancelled: _cancelled?.future,
+      );
+      if (!_operationActive) return;
       final date = DateTime.now().toIso8601String().substring(0, 10);
       final saved = await FilePicker.saveFile(
         fileName: 'XMPlus-$date${includeAccount ? '-含账号' : ''}.zip',
         bytes: Uint8List.fromList(bytes),
         mimeType: 'application/zip',
         dialogTitle: '保存备份',
       );
-      if (saved != null && mounted)
+      if (saved != null && _operationActive)
         setState(() {
           AppLog.instance.trace(
             "lib/pages/backup_page.dart::_BackupPageState._export.closure#1.closure#1",
@@ -188,21 +230,34 @@ class _BackupPageState extends State<BackupPage> {
         type: FileType.custom,
         allowedExtensions: ['zip'],
       );
-      if (file == null || !mounted) return;
+      if (file == null || !_operationActive) return;
       final length = await file.length();
+      if (!_operationActive) return;
       if (length != null && length > ConfigArchive.maxBytes) {
         throw const ConfigArchiveException('备份超过 64 MiB');
       }
       // A bounded stream also handles providers which do not report file length.
       final bytes = BytesBuilder(copy: false);
-      await for (final chunk in file.readAsByteStream()) {
-        if (bytes.length + chunk.length > ConfigArchive.maxBytes) {
-          throw const ConfigArchiveException('备份超过 64 MiB');
+      final stream = _importStream = StreamIterator(file.readAsByteStream());
+      try {
+        while (await stream.moveNext()) {
+          if (!_operationActive) return;
+          final chunk = stream.current;
+          if (bytes.length + chunk.length > ConfigArchive.maxBytes) {
+            throw const ConfigArchiveException('备份超过 64 MiB');
+          }
+          bytes.add(chunk);
         }
-        bytes.add(chunk);
+      } finally {
+        _importStream = null;
+        await stream.cancel();
       }
-      final draft = await _archive.inspect(bytes.takeBytes());
-      if (!mounted) return;
+      if (!_operationActive) return;
+      final draft = await _archive.inspect(
+        bytes.takeBytes(),
+        cancelled: _cancelled?.future,
+      );
+      if (!_operationActive) return;
       final replacements = <String, String>{};
       for (final oldRoot in draft.missingDirectories) {
         if (!await _confirm(
@@ -211,11 +266,11 @@ class _BackupPageState extends State<BackupPage> {
           '选择目录',
         ))
           return;
-        if (!mounted) return;
+        if (!_operationActive) return;
         final selected = await FilePicker.getDirectoryPath(
           dialogTitle: '选择新的下载目录',
         );
-        if (selected == null || !mounted) return;
+        if (selected == null || !_operationActive) return;
         replacements[oldRoot] = selected;
       }
       final accepted = await _confirm(
@@ -236,7 +291,7 @@ class _BackupPageState extends State<BackupPage> {
         ),
         '确认恢复',
       );
-      if (!accepted || !mounted) return;
+      if (!accepted || !_operationActive) return;
       try {
         await widget.runtime.restoreBackup(draft, relocatedRoots: replacements);
       } catch (_) {
@@ -266,14 +321,22 @@ class _BackupPageState extends State<BackupPage> {
   @override
   Widget build(BuildContext context) {
     AppLog.instance.trace("lib/pages/backup_page.dart::_BackupPageState.build");
-    return ListenableBuilder(
-      listenable: widget.runtime,
-      builder: (context, _) {
+    return PopScope(
+      onPopInvokedWithResult: (didPop, _) {
         AppLog.instance.trace(
           "lib/pages/backup_page.dart::_BackupPageState.build.closure#1",
         );
-        return _content(context);
+        if (didPop) _cancelOperation();
       },
+      child: ListenableBuilder(
+        listenable: widget.runtime,
+        builder: (context, _) {
+          AppLog.instance.trace(
+            "lib/pages/backup_page.dart::_BackupPageState.build.closure#2",
+          );
+          return _content(context);
+        },
+      ),
     );
   }
 

lib/pages/developer_settings_page.dart

@@ -30,6 +30,14 @@ class _DeveloperSettingsPageState extends State<DeveloperSettingsPage> {
   String? _selected;
   String? _error;
   bool _busy = false;
+  bool _leaving = false;
+
+  bool _canContinueExport() {
+    AppLog.instance.trace(
+      "lib/pages/developer_settings_page.dart::_DeveloperSettingsPageState._canContinueExport",
+    );
+    return mounted && !_leaving;
+  }
 
   @override
   void initState() {
@@ -202,7 +210,7 @@ class _DeveloperSettingsPageState extends State<DeveloperSettingsPage> {
         "lib/pages/developer_settings_page.dart::_DeveloperSettingsPageState._export.closure#1",
       );
 
-      if (_busy) return;
+      if (_busy || !_canContinueExport()) return;
       final session = _sessions.where((session) {
         AppLog.instance.trace(
           "lib/pages/developer_settings_page.dart::_DeveloperSettingsPageState._export.closure#1.closure#1",
@@ -221,19 +229,25 @@ class _DeveloperSettingsPageState extends State<DeveloperSettingsPage> {
       try {
         if (clipboard) {
           final snapshot = await _log.snapshot(session.fileName);
+          if (!_canContinueExport()) return;
           if (!snapshot.canCopyToClipboard(android: Platform.isAndroid)) {
             throw StateError('日志过大，无法完整复制，请导出到文件');
           }
           final text = await snapshot.readForClipboard(
             android: Platform.isAndroid,
           );
+          if (!_canContinueExport()) return;
           await Clipboard.setData(ClipboardData(text: text));
-          if (mounted) _message('日志已复制');
+          if (_canContinueExport()) _message('日志已复制');
         } else {
-          final destination = await exportLogSession(session);
-          if (destination != null && mounted) _message('日志已导出');
+          final destination = await exportLogSession(
+            session,
+            canStart: _canContinueExport,
+          );
+          if (destination != null && _canContinueExport()) _message('日志已导出');
         }
       } catch (error, stack) {
+        if (!_canContinueExport()) return;
         if (!_log.errorWasRecorded(error)) {
           _log.write(
             AppLogLevel.warning,
@@ -301,7 +315,7 @@ class _DeveloperSettingsPageState extends State<DeveloperSettingsPage> {
       "lib/pages/developer_settings_page.dart::_DeveloperSettingsPageState.build",
     );
 
-    return ListenableBuilder(
+    final content = ListenableBuilder(
       listenable: widget.runtime,
       builder: (context, _) {
         AppLog.instance.trace(
@@ -515,5 +529,14 @@ class _DeveloperSettingsPageState extends State<DeveloperSettingsPage> {
         );
       },
     );
+    return PopScope(
+      child: content,
+      onPopInvokedWithResult: (didPop, _) {
+        AppLog.instance.trace(
+          "lib/pages/developer_settings_page.dart::_DeveloperSettingsPageState.build.closure#2",
+        );
+        if (didPop) _leaving = true;
+      },
+    );
   }
 }

lib/services/log_export.dart

@@ -8,16 +8,19 @@ import 'android_platform.dart';
 import 'app_log.dart';
 
 /// Exports only a session returned by the logger, never an arbitrary path.
-/// A null result means the user cancelled the platform save dialog.
-Future<Uri?> exportLogSession(LogSession session) {
+/// A null result means the caller or the platform save dialog cancelled.
+/// [canStart] gates preparation; an opened save dialog can still finish.
+Future<Uri?> exportLogSession(LogSession session, {bool Function()? canStart}) {
   AppLog.instance.trace("lib/services/log_export.dart::exportLogSession");
   return AppLog.instance.runWithErrorScope(() async {
     AppLog.instance.trace(
       "lib/services/log_export.dart::exportLogSession.closure#1",
     );
 
+    if (canStart?.call() == false) return null;
     final log = AppLog.instance;
     final sessions = await log.sessions();
+    if (canStart?.call() == false) return null;
     if (!sessions.any((candidate) {
       AppLog.instance.trace(
         "lib/services/log_export.dart::exportLogSession.closure#1.closure#1",
@@ -35,6 +38,7 @@ Future<Uri?> exportLogSession(LogSession session) {
       throw ArgumentError.value(name, 'fileName', '日志文件名无效');
     }
     final snapshot = await log.snapshot(name);
+    if (canStart?.call() == false) return null;
     if (Platform.isAndroid) {
       return AndroidPlatform.exportLogSnapshot(snapshot, name);
     }