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在开发项目里修改用户头像的功能，涉及到图片选取及裁剪，基本实现步骤如下：

1、pubspec.yaml 添加 image_picker: ^1.0.1  image_cropper: ^4.0.1：

dependencies:image_picker: ^1.0.1image_cropper: ^4.0.1flutter:sdk: flutter

2、AndroidManifest.xml 添加：

<activityandroid:name="com.yalantis.ucrop.UCropActivity"android:screenOrientation="portrait"android:theme="@style/Theme.AppCompat.Light.NoActionBar"/>

3、封装工具类 image_picker_helper.dart ，代码如下：

import 'dart:io';import 'package:flutter/material.dart';
import 'package:image_cropper/image_cropper.dart';
import 'package:image_picker/image_picker.dart';/// @description: 从相册或照相机里选取图片的工具，带裁剪功能
class ImagePickerHelper {BuildContext buildContext;ImagePickerHelper(this.buildContext);void pickImage(ImageSource source, ImagePickerCallback? callback) {ImagePicker().pickImage(source: source).then((image) {if (image == null) return;if (callback == null) return;callback.call(image);}).onError((error, stackTrace) {debugPrint("获取图片失败:$error");});}void cropImage(File originalImage, ImageCropCallback? callback) {Future<CroppedFile?> future = ImageCropper().cropImage(sourcePath: originalImage.path,maxWidth: 100,maxHeight: 100,uiSettings: [AndroidUiSettings(toolbarTitle: '',toolbarColor: Colors.white,statusBarColor: Colors.white,toolbarWidgetColor: Colors.green,initAspectRatio: CropAspectRatioPreset.square,lockAspectRatio: false),IOSUiSettings(title: '',),WebUiSettings(context: buildContext,),],);future.then((value) {debugPrint("_cropImage path:${value == null ? "" : value.path}");if (value == null) return;if (callback == null) return;callback.call(value);}).onError((error, stackTrace) {debugPrint("裁剪图片失败:$error");});}void pickWithCropImage(ImageSource source, ImageCropCallback? callback) {pickImage(source, (xFile) {cropImage(File(xFile.path), callback);});}
}typedef ImagePickerCallback = void Function(XFile xFile);
typedef ImageCropCallback = void Function(CroppedFile croppedFile);

4、使用示例：

//ImageSource.camera 照相机 或 ImageSource.gallery 相册ImagePickerHelper(context).pickWithCropImage(ImageSource.gallery,(croppedFile) {//获取到剪切的文件路径，进行相关的操作debugPrint("croppedFile:${croppedFile.path}");});