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lib/pages/epub_reader/page_turn/android_page_turn_session.dart

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+import 'dart:async';
+import 'dart:ui' as ui;
+
+import 'package:flutter/material.dart';
+
+import '../reader_webview.dart';
+
+class AndroidPageTurnSession {
+  late final AnimationController _animController;
+  late Animation<Offset> _slideAnimation;
+  ui.Image? _screenshotData;
+  bool _isAnimating = false;
+  bool _isForwardAnimation = true;
+  int _pageTurnToken = 0;
+
+  AndroidPageTurnSession({
+    required TickerProvider vsync,
+    required Duration duration,
+  }) {
+    _animController = AnimationController(vsync: vsync, duration: duration);
+    _slideAnimation = Tween<Offset>(
+      begin: Offset.zero,
+      end: Offset.zero,
+    ).animate(_animController);
+  }
+
+  void dispose() {
+    _screenshotData?.dispose();
+    _animController.dispose();
+  }
+
+  void _setupTween(bool isNext, bool isVertical) {
+    Tween<Offset> tween;
+    if (isNext) {
+      tween = Tween<Offset>(
+        begin: Offset.zero,
+        end: Offset(isVertical ? 1.0 : -1.0, 0.0),
+      );
+    } else {
+      tween = Tween<Offset>(
+        begin: Offset(isVertical ? 1.0 : -1.0, 0.0),
+        end: Offset.zero,
+      );
+    }
+    _slideAnimation = CurvedAnimation(
+      parent: _animController,
+      curve: Curves.easeOut,
+    ).drive(tween);
+  }
+
+  Future<ui.Image?> _takeScreenshot(
+    ReaderWebViewController webViewController,
+  ) async {
+    ui.Image? screenshot;
+    try {
+      screenshot = await webViewController.takeScreenshot();
+    } catch (e) {
+      debugPrint('Error taking screenshot: $e');
+      screenshot = null;
+    }
+    return screenshot;
+  }
+
+  Future<void> perform({
+    required ReaderWebViewController webViewController,
+    required bool needAnimation,
+    required bool isNext,
+    required bool isVertical,
+    required Future<void> Function(bool) onPerformPageTurn,
+    required void Function(VoidCallback) setState,
+    required bool Function() isMounted,
+  }) async {
+    if (!needAnimation) {
+      await onPerformPageTurn(isNext);
+      return;
+    }
+
+    final int turnToken = ++_pageTurnToken;
+
+    final screenshot = await _takeScreenshot(webViewController);
+
+    // If screenshot fails, just perform the page turn without animation
+    if (screenshot == null) {
+      _screenshotData?.dispose();
+      _screenshotData = null;
+      _animController.reset();
+      await onPerformPageTurn(isNext);
+      return;
+    }
+
+    // If the widget has been unmounted or a new page turn has started, dispose the screenshot and exit
+    if (!isMounted() || turnToken != _pageTurnToken) {
+      screenshot.dispose();
+      return;
+    }
+
+    setState(() {
+      _isForwardAnimation = isNext;
+      _screenshotData?.dispose();
+      _screenshotData = screenshot;
+      _isAnimating = true;
+
+      _setupTween(isNext, isVertical);
+      _animController.reset();
+    });
+
+    // Perform the page turn in parallel with the animation
+    await onPerformPageTurn(isNext);
+
+    // Start the animation
+    if (!isMounted() || turnToken != _pageTurnToken) {
+      return;
+    }
+
+    try {
+      await _animController.forward();
+    } finally {
+      if (turnToken == _pageTurnToken) {
+        final finishedScreenshot = _screenshotData;
+        if (isMounted()) {
+          setState(() {
+            _screenshotData = null;
+            _isAnimating = false;
+          });
+        } else {
+          _screenshotData = null;
+          _isAnimating = false;
+        }
+        finishedScreenshot?.dispose();
+
+        _animController.reset();
+        _isAnimating = false;
+      }
+    }
+  }
+
+  Widget buildAnimatedContainer(
+    BuildContext context,
+    Widget child,
+    Widget Function(ui.Image?) buildScreenshotContainer,
+  ) {
+    return Stack(
+      children: [
+        // Backward animation: show the current page as the background
+        if (_isAnimating && !_isForwardAnimation)
+          Positioned.fill(child: buildScreenshotContainer(_screenshotData)),
+        // Webview page: slide it in from the left for backward animation, or keep it static for forward animation
+        Positioned.fill(
+          child: SlideTransition(
+            position: _isAnimating && !_isForwardAnimation
+                ? _slideAnimation
+                : const AlwaysStoppedAnimation(Offset.zero),
+            child: child,
+          ),
+        ),
+        // Forward animation: slide the current page out to the right
+        if (_isAnimating && _isForwardAnimation)
+          Positioned.fill(
+            child: SlideTransition(
+              position: _slideAnimation,
+              child: buildScreenshotContainer(_screenshotData),
+            ),
+          ),
+      ],
+    );
+  }
+
+  bool get isAnimating => _isAnimating;
+}

lib/pages/epub_reader/page_turn/ios_page_turn_session.dart

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+import 'dart:async';
+import 'dart:io';
+
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+class IOSPageTurnSession {
+  static const MethodChannel _nativePageTurnChannel = MethodChannel(
+    'mooknote/reader_page_turn',
+  );
+
+  int _currentToken = 0;
+  bool _isAnimating = false;
+
+  Future<void> _prepareIOSPageTurn() async {
+    if (!Platform.isIOS) return;
+    try {
+      await _nativePageTurnChannel.invokeMethod<void>('preparePageTurn');
+    } on MissingPluginException {
+      // no-op for configurations without iOS native channel
+    } catch (e) {
+      debugPrint('preparePageTurn failed: $e');
+    }
+  }
+
+  Future<void> _animateIOSPageTurn(bool isNext, bool isVertical) async {
+    if (!Platform.isIOS) return;
+    try {
+      final token = ++_currentToken;
+      _isAnimating = true;
+      await _nativePageTurnChannel.invokeMethod<void>('animatePageTurn', {
+        'isNext': isNext,
+        'isVertical': isVertical,
+      });
+      if (token == _currentToken) {
+        _isAnimating = false;
+        return;
+      }
+    } on MissingPluginException {
+      // no-op for configurations without iOS native channel
+    } catch (e) {
+      debugPrint('animatePageTurn failed: $e');
+    }
+  }
+
+  Future<void> perform({
+    required bool needAnimation,
+    required bool isNext,
+    required bool isVertical,
+    required Future<void> Function(bool) onPerformPageTurn,
+  }) async {
+    if (!needAnimation) {
+      await onPerformPageTurn(isNext);
+      return;
+    }
+
+    await _prepareIOSPageTurn();
+    await onPerformPageTurn(isNext);
+    unawaited(_animateIOSPageTurn(isNext, isVertical));
+  }
+
+  Widget buildAnimatedContainer(BuildContext context, Widget child) {
+    return child;
+  }
+
+  bool get isAnimating => _isAnimating;
+}

lib/pages/epub_reader/page_turn/page_turn.dart

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+export 'android_page_turn_session.dart';
+export 'ios_page_turn_session.dart';