308 lines
9.3 KiB
Dart
308 lines
9.3 KiB
Dart
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/// 封面/宣传图裁剪页：固定纵横比交互裁剪 → 等比缩放上限 → JPEG 落盘。
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///
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/// 输入 image_picker 选中的本机路径；输出裁剪后的临时文件路径
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/// （`{tmp}/album_assets/crop_{ms}.jpg`）；取消/失败返回 null。
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/// 封面 16:9（输出宽 ≤1920）、宣传图 3:1（输出宽 ≤2400）由调用方给定。
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///
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/// crop_your_image 2.0.0 为回调式 API：`CropController.crop()` 是 void，
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/// 裁剪结果经 `onCropped` 回调（`CropSuccess.croppedImage` /
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/// `CropFailure.cause`）。像素级 decode/缩放/编码统一放
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/// `Isolate.run`，避免大图卡死主 isolate。
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library;
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import 'dart:io';
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import 'dart:isolate';
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import 'dart:typed_data';
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import 'package:crop_your_image/crop_your_image.dart';
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import 'package:flutter/material.dart';
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import 'package:image/image.dart' as img;
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import '../l10n/app_localizations.dart';
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import '../ui/tokens.dart';
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/// 裁剪页输出目录（应用临时目录下的 album_assets；测试直接可用真实 FS）。
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Directory _cropOutputDir() {
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final dir = Directory(
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'${Directory.systemTemp.path}${Platform.pathSeparator}album_assets',
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);
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dir.createSync(recursive: true);
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return dir;
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}
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/// 裁剪字节 → 可解码格式预检（魔数嗅探；HEIC/GIF 等走不支持提示）。
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///
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/// 包内解析失败（`_parseImageWith` 的 compute 抛错）不会回调页面——
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/// 页面在交给 [Crop] 前先嗅探，拦下注定解析失败的源。
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/// GIF 明确不支持：包内 formatDetector 的兜底分支按 png 解码
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/// （`_ => ImageFormat.png`），decodePng(gif) 必然失败 → onStatusChanged
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/// 永不 ready → 页面挂死在加载态。
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bool _hasSupportedSignature(Uint8List bytes) {
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if (bytes.length < 12) {
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return false;
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}
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final jpeg = bytes[0] == 0xFF && bytes[1] == 0xD8 && bytes[2] == 0xFF;
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final png =
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bytes[0] == 0x89 &&
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bytes[1] == 0x50 &&
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bytes[2] == 0x4E &&
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bytes[3] == 0x47;
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final bmp = bytes[0] == 0x42 && bytes[1] == 0x4D;
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final webp =
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bytes[0] == 0x52 &&
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bytes[1] == 0x49 &&
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bytes[2] == 0x46 &&
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bytes[3] == 0x46 &&
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bytes[8] == 0x57 &&
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bytes[9] == 0x45 &&
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bytes[10] == 0x42 &&
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bytes[11] == 0x50;
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return jpeg || png || bmp || webp;
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}
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/// 裁剪输出编码 + 落盘（只在 isolate 内执行）。
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String _encodeCropToJpeg(Uint8List cropped, int? maxOutputWidth) {
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final decoded = img.decodeImage(cropped);
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if (decoded == null) {
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throw img.ImageException('crop output is not decodable');
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}
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var output = decoded;
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if (maxOutputWidth != null && decoded.width > maxOutputWidth) {
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output = img.copyResize(decoded, width: maxOutputWidth);
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}
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final file = File(
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'${_cropOutputDir().path}${Platform.pathSeparator}'
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'crop_${DateTime.now().millisecondsSinceEpoch}.jpg',
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);
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file.writeAsBytesSync(img.encodeJpg(output, quality: 90));
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return file.path;
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}
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/// 封面/宣传图裁剪页。
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class ImageCropPage extends StatefulWidget {
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const ImageCropPage({
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super.key,
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required this.sourcePath,
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required this.aspectRatio,
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this.maxOutputWidth,
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});
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/// 源图本机路径（image_picker 单选返回）。
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final String sourcePath;
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/// 目标宽高比（宽/高）：封面 16/9、宣传图 3/1。
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final double aspectRatio;
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/// 输出宽度上限（等比缩放；null=保持裁剪原分辨率）。
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final int? maxOutputWidth;
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@override
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State<ImageCropPage> createState() => _ImageCropPageState();
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}
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class _ImageCropPageState extends State<ImageCropPage> {
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final CropController _controller = CropController();
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late final Future<Uint8List> _sourceBytes;
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/// 源读取完成且魔数预检通过（可裁剪）。
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bool _ready = false;
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/// 包内解析完成（CropStatus.ready；完成按钮需等解析完再开放）。
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bool _cropReady = false;
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/// 源读取失败或预检不通过（HEIC 等不支持的格式）。
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bool _unsupported = false;
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/// 编码落盘中（遮罩 + 防重复点击）。
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bool _processing = false;
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@override
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void initState() {
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super.initState();
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_sourceBytes = File(widget.sourcePath).readAsBytes();
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_sourceBytes
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.then((bytes) {
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if (!mounted) {
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return;
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}
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setState(() {
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_ready = _hasSupportedSignature(bytes);
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_unsupported = !_ready;
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});
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})
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.catchError((Object _) {
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if (!mounted) {
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return;
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}
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setState(() => _unsupported = true);
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});
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}
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void _cancel() {
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Navigator.of(context).pop(null);
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}
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void _confirm() {
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if (_processing || !_ready || !_cropReady) {
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return;
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}
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setState(() => _processing = true);
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// crop() 为 void：结果经 onCropped 回调。
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_controller.crop();
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}
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/// 包内状态回调：解析完成（ready）才允许确认，防 crop() 在解析前触发的断言。
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void _onCropStatus(CropStatus status) {
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final ready = status == CropStatus.ready;
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if (ready == _cropReady) {
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return;
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}
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setState(() => _cropReady = ready);
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}
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Future<void> _onCropped(CropResult result) async {
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if (!mounted) {
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return;
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}
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if (result is! CropSuccess) {
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_fail();
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return;
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}
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// 仅捕获可发送值（Uint8List/int），闭包跨 isolate 复制。
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final cropped = result.croppedImage;
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final maxWidth = widget.maxOutputWidth;
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try {
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final outputPath = await Isolate.run(
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() => _encodeCropToJpeg(cropped, maxWidth),
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);
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if (!mounted) {
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return;
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}
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Navigator.of(context).pop(outputPath);
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} on Object {
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if (!mounted) {
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return;
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}
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_fail();
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}
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}
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/// 裁剪/编码失败：解除遮罩 + 提示，不 pop。
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void _fail() {
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setState(() => _processing = false);
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ScaffoldMessenger.of(context).showSnackBar(
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SnackBar(
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content: Text(AppLocalizations.of(context).cropUnsupportedFormat),
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),
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);
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}
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@override
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Widget build(BuildContext context) {
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final l10n = AppLocalizations.of(context);
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// 编码落盘中拦截系统返回/ AppBar 返回（与底部取消禁用一致）。
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return PopScope(
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canPop: !_processing,
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child: Scaffold(
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appBar: AppBar(title: Text(l10n.cropTitle)),
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body: Stack(
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children: [
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Positioned.fill(child: _buildBody(l10n)),
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if (_processing)
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Positioned.fill(
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child: AbsorbPointer(
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child: ColoredBox(
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color: Colors.black54,
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child: Center(
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child: Column(
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mainAxisSize: MainAxisSize.min,
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children: [
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const CircularProgressIndicator(),
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const SizedBox(height: kSpace12),
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Text(
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l10n.cropProcessing,
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style: TextStyle(
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color: Theme.of(context).colorScheme.onPrimary,
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),
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),
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],
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),
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),
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),
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),
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),
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],
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),
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bottomNavigationBar: SafeArea(
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child: Padding(
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padding: const EdgeInsets.fromLTRB(
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kSpace16,
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kSpace8,
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kSpace16,
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kSpace12,
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),
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child: Row(
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children: [
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Expanded(
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child: TextButton(
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onPressed: _processing ? null : _cancel,
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child: Text(l10n.cropCancel),
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),
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),
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const SizedBox(width: kSpace12),
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Expanded(
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child: FilledButton(
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onPressed: (_ready && _cropReady && !_processing)
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? _confirm
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: null,
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child: Text(l10n.cropConfirm),
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),
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),
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],
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),
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),
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),
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),
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);
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}
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Widget _buildBody(AppLocalizations l10n) {
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if (_unsupported) {
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return Center(
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child: Padding(
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padding: const EdgeInsets.all(kSpace16),
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child: Text(
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l10n.cropUnsupportedFormat,
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textAlign: TextAlign.center,
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style: Theme.of(context).textTheme.bodyMedium?.copyWith(
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color: Theme.of(context).colorScheme.onSurfaceVariant,
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),
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),
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),
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);
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}
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return FutureBuilder<Uint8List>(
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future: _sourceBytes,
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builder: (context, snapshot) {
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if (snapshot.connectionState != ConnectionState.done ||
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!snapshot.hasData) {
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return const Center(child: CircularProgressIndicator());
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}
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return Crop(
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image: snapshot.data!,
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controller: _controller,
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onCropped: _onCropped,
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onStatusChanged: _onCropStatus,
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aspectRatio: widget.aspectRatio,
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// 交互模式 + 锁定裁剪框：用户平移/缩放图片适配固定比例框。
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interactive: true,
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fixCropRect: true,
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baseColor: Theme.of(context).colorScheme.surfaceContainerHighest,
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progressIndicator: const CircularProgressIndicator(strokeWidth: 2),
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);
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},
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);
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}
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}
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