Flutter图片裁剪插件 native_image_cropper_android 的使用

native_image_cropper_android 是一个用于 Android 平台的图片裁剪插件，它是 native_image_cropper 插件的一部分。该插件提供了在 Android 设备上进行高效图片裁剪的功能。

使用说明

这个插件是被认可的（endorsed），这意味着你可以直接使用 native_image_cropper 插件，并且当你这样做时，native_image_cropper_android 会自动包含在你的应用中。

示例代码

以下是一个完整的示例 demo，展示了如何使用 native_image_cropper_android 插件来裁剪图片：

import 'dart:async';
import 'dart:typed_data';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:native_image_cropper_android/native_image_cropper_android.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  static const String imageName = 'sail-boat.png';

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  final _nativeImageCropperAndroidPlugin = NativeImageCropperAndroid();
  ImageFormat _format = ImageFormat.jpg;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Native Image Cropper Android Example'),
        ),
        body: FutureBuilder<Uint8List>(
          future: _getBytes(),
          builder: (context, snapshot) {
            if (snapshot.hasData) {
              final bytes = snapshot.data!;
              return Column(
                children: [
                  Image(
                    image: MemoryImage(bytes),
                  ),
                  const SizedBox(height: 20),
                  Row(
                    mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                    children: [
                      DropdownButton<ImageFormat>(
                        value: _format,
                        items: const [
                          DropdownMenuItem(value: ImageFormat.jpg, child: Text('JPG')),
                          DropdownMenuItem(value: ImageFormat.png, child: Text('PNG')),
                        ],
                        onChanged: (value) => setState(() => _format = value!),
                      ),
                      ElevatedButton(
                        onPressed: () => _crop(
                          context: context,
                          bytes: bytes,
                          method: _nativeImageCropperAndroidPlugin.cropRect,
                        ),
                        child: const Icon(Icons.crop),
                      ),
                      ElevatedButton(
                        onPressed: () => _crop(
                          context: context,
                          bytes: bytes,
                          method: _nativeImageCropperAndroidPlugin.cropOval,
                        ),
                        child: const Icon(Icons.crop),
                      ),
                    ],
                  ),
                ],
              );
            }
            return const Center(child: CircularProgressIndicator());
          },
        ),
      ),
    );
  }

  Future<void> _crop({
    required BuildContext context,
    required Uint8List bytes,
    required Future<Uint8List> Function({
      required Uint8List bytes,
      required int x,
      required int y,
      required int width,
      required int height,
      required ImageFormat format,
    }) method,
  }) async {
    final croppedBytes = await method(
      bytes: bytes,
      x: 0,
      y: 0,
      width: 2999,
      height: 1999,
      format: _format,
    );

    if (context.mounted) {
      Navigator.push<void>(
        context,
        MaterialPageRoute<ResultPage>(
          builder: (context) => ResultPage(
            bytes: croppedBytes,
            format: _format,
          ),
        ),
      );
    }
  }

  Future<Uint8List> _getBytes() async {
    final byteData = await rootBundle.load('assets/${MyApp.imageName}');
    return byteData.buffer.asUint8List();
  }
}

class ResultPage extends StatelessWidget {
  final Uint8List bytes;
  final ImageFormat format;

  const ResultPage({required this.bytes, required this.format, super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Cropped Image - ${format.name.toUpperCase()}'),
      ),
      body: Center(
        child: Image.memory(bytes),
      ),
    );
  }
}

注意事项

1. 导入资源：确保在 pubspec.yaml 文件中正确配置了资源文件路径：

   assets:
     - assets/sail-boat.png
   

2. 插件安装：在 pubspec.yaml 中添加 native_image_cropper 依赖：

   dependencies:
     flutter:
       sdk: flutter
     native_image_cropper: ^版本号
   

3. 权限设置：确保在 Android 端的 AndroidManifest.xml 文件中声明了读写存储权限：

   <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
   <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>