Asynchronous 用于图像散列的颤振计算函数
hii我正在尝试实现计算功能。我正在尝试使用image_picker插件通过摄像头单击图像。然后我尝试获取图像文件的哈希摘要。由于这是一个非常激烈的操作，我试图使用compute函数，但无法做到这一点。 这就是我到目前为止所做的Asynchronous 用于图像散列的颤振计算函数,asynchronous,flutter,strong-typing,Asynchronous,Flutter,Strong Typing,hii我正在尝试实现计算功能。我正在尝试使用image_picker插件通过摄像头单击图像。然后我尝试获取图像文件的哈希摘要。由于这是一个非常激烈的操作，我试图使用compute函数，但无法做到这一点。 这就是我到目前为止所做的 final File picture = await ImagePicker.pickImage( source: ImageSource.camera); setState(() { _imageFile = picture;
final File picture = await ImagePicker.pickImage(
source: ImageSource.camera);
setState(() {
_imageFile = picture;
});
var result = await compute(generateImageHash(), _imageFile);
print(result);
generateImageHash() async{
var image_bytes = _imageFile.readAsBytesSync().toString();
var bytes = utf8.encode(image_bytes); // data being hashed
String digest = sha256.convert(bytes).toString();
print("This is image Digest : $digest");
return digest;
}
Unhandled Exception: type 'Future<dynamic>' is not a subtype of type '(File) => FutureOr<dynamic>'
未处理的异常：类型“Future”不是类型“（文件）=>FutureOr”的子类型
我不熟悉强类型语言，请帮助。谢谢第一期请更改
var result = await compute(generateImageHash(), _imageFile);
相似的 第二个问题请从计算中删除wait关键字
var result = compute(generateImageHash, _imageFile);
Future<String> generateImageHash(File file) async{
Future generateImageHash（文件）异步{
// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'dart:async';
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:image_picker/image_picker.dart';
import 'package:video_player/video_player.dart';
import 'dart:async';
import 'dart:convert';
import 'package:flutter/foundation.dart';
import 'package:crypto/crypto.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Image Picker Demo',
home: MyHomePage(title: 'Image Picker Example'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
Future<String> generateImageHash(File file) async{
var image_bytes = file.readAsBytesSync().toString();
var bytes = utf8.encode(image_bytes); // data being hashed
String digest = sha256.convert(bytes).toString();
print("This is image Digest : $digest");
return digest;
}
class _MyHomePageState extends State<MyHomePage> {
File _imageFile;
dynamic _pickImageError;
bool isVideo = false;
VideoPlayerController _controller;
String _retrieveDataError;
void _onImageButtonPressed(ImageSource source) async {
if (_controller != null) {
_controller.setVolume(0.0);
_controller.removeListener(_onVideoControllerUpdate);
}
if (isVideo) {
ImagePicker.pickVideo(source: source).then((File file) {
if (file != null && mounted) {
setState(() {
_controller = VideoPlayerController.file(file)
..addListener(_onVideoControllerUpdate)
..setVolume(1.0)
..initialize()
..setLooping(true)
..play();
});
}
});
} else {
try {
print("_imageFile start");
_imageFile = await ImagePicker.pickImage(source: source);
print("_imageFile end");
print("compute start");
var result = compute(generateImageHash, _imageFile);
print("compute end");
print(result);
} catch (e) {
_pickImageError = e;
}
setState(() {});
}
}
void _onVideoControllerUpdate() {
setState(() {});
}
@override
void deactivate() {
if (_controller != null) {
_controller.setVolume(0.0);
_controller.removeListener(_onVideoControllerUpdate);
}
super.deactivate();
}
@override
void dispose() {
if (_controller != null) {
_controller.dispose();
}
super.dispose();
}
Widget _previewVideo(VideoPlayerController controller) {
final Text retrieveError = _getRetrieveErrorWidget();
if (retrieveError != null) {
return retrieveError;
}
if (controller == null) {
return const Text(
'You have not yet picked a video',
textAlign: TextAlign.center,
);
} else if (controller.value.initialized) {
return Padding(
padding: const EdgeInsets.all(10.0),
child: AspectRatioVideo(controller),
);
} else {
return const Text(
'Error Loading Video',
textAlign: TextAlign.center,
);
}
}
Widget _previewImage() {
final Text retrieveError = _getRetrieveErrorWidget();
if (retrieveError != null) {
return retrieveError;
}
if (_imageFile != null) {
return Image.file(_imageFile);
} else if (_pickImageError != null) {
return Text(
'Pick image error: $_pickImageError',
textAlign: TextAlign.center,
);
} else {
return const Text(
'You have not yet picked an image.',
textAlign: TextAlign.center,
);
}
}
Future<void> retrieveLostData() async {
final LostDataResponse response = await ImagePicker.retrieveLostData();
if (response.isEmpty) {
return;
}
if (response.file != null) {
setState(() {
if (response.type == RetrieveType.video) {
isVideo = true;
_controller = VideoPlayerController.file(response.file)
..addListener(_onVideoControllerUpdate)
..setVolume(1.0)
..initialize()
..setLooping(true)
..play();
} else {
isVideo = false;
_imageFile = response.file;
}
});
} else {
_retrieveDataError = response.exception.code;
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Platform.isAndroid
? FutureBuilder<void>(
future: retrieveLostData(),
builder: (BuildContext context, AsyncSnapshot<void> snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
case ConnectionState.waiting:
return const Text(
'You have not yet picked an image.',
textAlign: TextAlign.center,
);
case ConnectionState.done:
return isVideo
? _previewVideo(_controller)
: _previewImage();
default:
if (snapshot.hasError) {
return Text(
'Pick image/video error: ${snapshot.error}}',
textAlign: TextAlign.center,
);
} else {
return const Text(
'You have not yet picked an image.',
textAlign: TextAlign.center,
);
}
}
},
)
: (isVideo ? _previewVideo(_controller) : _previewImage()),
),
floatingActionButton: Column(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
FloatingActionButton(
onPressed: () {
isVideo = false;
_onImageButtonPressed(ImageSource.gallery);
},
heroTag: 'image0',
tooltip: 'Pick Image from gallery',
child: const Icon(Icons.photo_library),
),
Padding(
padding: const EdgeInsets.only(top: 16.0),
child: FloatingActionButton(
onPressed: () {
isVideo = false;
_onImageButtonPressed(ImageSource.camera);
},
heroTag: 'image1',
tooltip: 'Take a Photo',
child: const Icon(Icons.camera_alt),
),
),
Padding(
padding: const EdgeInsets.only(top: 16.0),
child: FloatingActionButton(
backgroundColor: Colors.red,
onPressed: () {
isVideo = true;
_onImageButtonPressed(ImageSource.gallery);
},
heroTag: 'video0',
tooltip: 'Pick Video from gallery',
child: const Icon(Icons.video_library),
),
),
Padding(
padding: const EdgeInsets.only(top: 16.0),
child: FloatingActionButton(
backgroundColor: Colors.red,
onPressed: () {
isVideo = true;
_onImageButtonPressed(ImageSource.camera);
},
heroTag: 'video1',
tooltip: 'Take a Video',
child: const Icon(Icons.videocam),
),
),
],
),
);
}
Text _getRetrieveErrorWidget() {
if (_retrieveDataError != null) {
final Text result = Text(_retrieveDataError);
_retrieveDataError = null;
return result;
}
return null;
}
}
class AspectRatioVideo extends StatefulWidget {
AspectRatioVideo(this.controller);
final VideoPlayerController controller;
@override
AspectRatioVideoState createState() => AspectRatioVideoState();
}
class AspectRatioVideoState extends State<AspectRatioVideo> {
VideoPlayerController get controller => widget.controller;
bool initialized = false;
void _onVideoControllerUpdate() {
if (!mounted) {
return;
}
if (initialized != controller.value.initialized) {
initialized = controller.value.initialized;
setState(() {});
}
}
@override
void initState() {
super.initState();
controller.addListener(_onVideoControllerUpdate);
}
@override
Widget build(BuildContext context) {
if (initialized) {
return Center(
child: AspectRatio(
aspectRatio: controller.value?.aspectRatio,
child: VideoPlayer(controller),
),
);
} else {
return Container();
}
}
}
//Chromium作者版权所有。保留所有权利。
//此源代码的使用受BSD样式许可证的约束，该许可证可以
//在许可证文件中找到。
导入“dart:async”；
导入“dart:io”；
进口“包装：颤振/材料.省道”；
导入“包：image_picker/image_picker.dart”；
导入“package:video_player/video_player.dart”；
导入“dart:async”；
导入“dart:convert”；
进口“包装：颤振/基础.dart”；
导入“包：crypto/crypto.dart”；
void main（）{
runApp（MyApp（））；
}
类MyApp扩展了无状态小部件{
@凌驾
小部件构建（构建上下文）{
返回材料PP(
标题：“图像选择器演示”，
主页：MyHomePage（标题：“图像选择器示例”），
);
}
}
类MyHomePage扩展StatefulWidget{
MyHomePage（{Key，this.title}）：超级（Key:Key）；
最后的字符串标题；
@凌驾
_MyHomePageState createState（）=>\u MyHomePageState（）；
}
Future generateImageHash（文件）异步{
var image_bytes=file.readAsBytesSync（）.toString（）；
var bytes=utf8.encode（图像字节）；//正在散列的数据
字符串摘要=sha256.convert（字节）.toString（）；
打印（“这是图像摘要：$Digest”）；
返回摘要；
}
类_MyHomePageState扩展状态{
文件imageFile；
动态误差；
bool isVideo=false；
视频播放控制器\u控制器；
字符串_retrieveDataError；
void _onImageButtonPressed（图像源）异步{
如果（_controller！=null）{
_控制器。设置音量（0.0）；
_控制器。removeListener（\u onVideoControllerUpdate）；
}
如果（isVideo）{
pickVideo（源代码：source）.then（（文件）{
if（文件！=null&&mounted）{
设置状态（）{
_控制器=VideoPlayerController.file（文件）
..addListener（视频控制器更新）
..设置音量（1.0）
…初始化（）
..设置循环（真）
…玩（）；
});
}
});
}否则{
试一试{
打印（“_imagefilestart”）；
_imageFile=await ImagePicker.pickImage（源：源）；
打印（“_imagefileend”）；
打印（“计算开始”）；
var result=compute（generateImageHash，_imageFile）；
打印（“计算结束”）；
打印（结果）；
}捕获（e）{
_pickImageError=e；
}
setState（（）{}）；
}
}
void _onVideoControllerUpdate（）{
setState（（）{}）；
}
@凌驾
无效停用（）{
如果（_controller！=null）{
_控制器。设置音量（0.0）；
_控制器。removeListener（\u onVideoControllerUpdate）；
}
super.deactivate（）；
}
@凌驾
无效处置（）{
如果（_controller！=null）{
_controller.dispose（）；
}
super.dispose（）；
}
小部件预览视频（视频播放器控制器）{
最终文本检索错误=_getRetrieveErrorWidget（）；
如果（retrieveError！=null）{
返回检索错误；
}
如果（控制器==null）{
返回常量文本(
“您尚未选择视频”，
textAlign:textAlign.center，
);
}else if（controller.value.initialized）{
返回填充(
填充：常数边集全部（10.0），
子项：AspectRatioVideo（控制器），
);
}否则{
返回常量文本(
“加载视频时出错”，
textAlign:textAlign.center，
);
}
}
小部件_previewImage（）{
最终文本检索错误=_getRetrieveErrorWidget（）；
如果（retrieveError！=null）{
返回检索错误；
}
如果（_imageFile！=null）{
返回Image.file（_imageFile）；
}else if（_pickImageError！=null）{
返回文本(
'拾取图像错误：$\u pickImageError'，
textAlign:textAlign.center，
);
}否则{
返回常量文本(
“您尚未选择图像。”，
textAlign:textAlign.center，
);
}
}
未来的检索速度数据（）异步{
最终LostDataResponse响应=等待ImagePicker.retrieveLostData（）；
if（response.isEmpty）{
返回；
}
if（response.file！=null）{
设置状态（）{
if（response.type==RetrieveType.video）{
isVideo=true；
_controller=VideoPlayerController.file（response.file）
..addListener（视频控制器更新）
..设置音量（1.0）
…初始化（）
..设置循环（真）
…玩（）；
}否则{
isVideo=false；
_imageFile=response.file；
}
});
}否则{
_retrieveDataError=response.exception.code；
}
}
@凌驾
小部件构建（构建上下文）{
返回脚手架(
appBar:appBar(
标题：文本（widget.title），
),
正文：中(
子：Platform.isAndroid
？未来建设者(
future:retrieveLostData（），
生成器：（BuildContext上下文，异步快照）{
交换机（快照.连接状态）
// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'dart:async';
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:image_picker/image_picker.dart';
import 'package:video_player/video_player.dart';
import 'dart:async';
import 'dart:convert';
import 'package:flutter/foundation.dart';
import 'package:crypto/crypto.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Image Picker Demo',
home: MyHomePage(title: 'Image Picker Example'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
Future<String> generateImageHash(File file) async{
var image_bytes = file.readAsBytesSync().toString();
var bytes = utf8.encode(image_bytes); // data being hashed
String digest = sha256.convert(bytes).toString();
print("This is image Digest : $digest");
return digest;
}
class _MyHomePageState extends State<MyHomePage> {
File _imageFile;
dynamic _pickImageError;
bool isVideo = false;
VideoPlayerController _controller;
String _retrieveDataError;
void _onImageButtonPressed(ImageSource source) async {
if (_controller != null) {
_controller.setVolume(0.0);
_controller.removeListener(_onVideoControllerUpdate);
}
if (isVideo) {
ImagePicker.pickVideo(source: source).then((File file) {
if (file != null && mounted) {
setState(() {
_controller = VideoPlayerController.file(file)
..addListener(_onVideoControllerUpdate)
..setVolume(1.0)
..initialize()
..setLooping(true)
..play();
});
}
});
} else {
try {
print("_imageFile start");
_imageFile = await ImagePicker.pickImage(source: source);
print("_imageFile end");
print("compute start");
var result = compute(generateImageHash, _imageFile);
print("compute end");
print(result);
} catch (e) {
_pickImageError = e;
}
setState(() {});
}
}
void _onVideoControllerUpdate() {
setState(() {});
}
@override
void deactivate() {
if (_controller != null) {
_controller.setVolume(0.0);
_controller.removeListener(_onVideoControllerUpdate);
}
super.deactivate();
}
@override
void dispose() {
if (_controller != null) {
_controller.dispose();
}
super.dispose();
}
Widget _previewVideo(VideoPlayerController controller) {
final Text retrieveError = _getRetrieveErrorWidget();
if (retrieveError != null) {
return retrieveError;
}
if (controller == null) {
return const Text(
'You have not yet picked a video',
textAlign: TextAlign.center,
);
} else if (controller.value.initialized) {
return Padding(
padding: const EdgeInsets.all(10.0),
child: AspectRatioVideo(controller),
);
} else {
return const Text(
'Error Loading Video',
textAlign: TextAlign.center,
);
}
}
Widget _previewImage() {
final Text retrieveError = _getRetrieveErrorWidget();
if (retrieveError != null) {
return retrieveError;
}
if (_imageFile != null) {
return Image.file(_imageFile);
} else if (_pickImageError != null) {
return Text(
'Pick image error: $_pickImageError',
textAlign: TextAlign.center,
);
} else {
return const Text(
'You have not yet picked an image.',
textAlign: TextAlign.center,
);
}
}
Future<void> retrieveLostData() async {
final LostDataResponse response = await ImagePicker.retrieveLostData();
if (response.isEmpty) {
return;
}
if (response.file != null) {
setState(() {
if (response.type == RetrieveType.video) {
isVideo = true;
_controller = VideoPlayerController.file(response.file)
..addListener(_onVideoControllerUpdate)
..setVolume(1.0)
..initialize()
..setLooping(true)
..play();
} else {
isVideo = false;
_imageFile = response.file;
}
});
} else {
_retrieveDataError = response.exception.code;
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Platform.isAndroid
? FutureBuilder<void>(
future: retrieveLostData(),
builder: (BuildContext context, AsyncSnapshot<void> snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
case ConnectionState.waiting:
return const Text(
'You have not yet picked an image.',
textAlign: TextAlign.center,
);
case ConnectionState.done:
return isVideo
? _previewVideo(_controller)
: _previewImage();
default:
if (snapshot.hasError) {
return Text(
'Pick image/video error: ${snapshot.error}}',
textAlign: TextAlign.center,
);
} else {
return const Text(
'You have not yet picked an image.',
textAlign: TextAlign.center,
);
}
}
},
)
: (isVideo ? _previewVideo(_controller) : _previewImage()),
),
floatingActionButton: Column(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
FloatingActionButton(
onPressed: () {
isVideo = false;
_onImageButtonPressed(ImageSource.gallery);
},
heroTag: 'image0',
tooltip: 'Pick Image from gallery',
child: const Icon(Icons.photo_library),
),
Padding(
padding: const EdgeInsets.only(top: 16.0),
child: FloatingActionButton(
onPressed: () {
isVideo = false;
_onImageButtonPressed(ImageSource.camera);
},
heroTag: 'image1',
tooltip: 'Take a Photo',
child: const Icon(Icons.camera_alt),
),
),
Padding(
padding: const EdgeInsets.only(top: 16.0),
child: FloatingActionButton(
backgroundColor: Colors.red,
onPressed: () {
isVideo = true;
_onImageButtonPressed(ImageSource.gallery);
},
heroTag: 'video0',
tooltip: 'Pick Video from gallery',
child: const Icon(Icons.video_library),
),
),
Padding(
padding: const EdgeInsets.only(top: 16.0),
child: FloatingActionButton(
backgroundColor: Colors.red,
onPressed: () {
isVideo = true;
_onImageButtonPressed(ImageSource.camera);
},
heroTag: 'video1',
tooltip: 'Take a Video',
child: const Icon(Icons.videocam),
),
),
],
),
);
}
Text _getRetrieveErrorWidget() {
if (_retrieveDataError != null) {
final Text result = Text(_retrieveDataError);
_retrieveDataError = null;
return result;
}
return null;
}
}
class AspectRatioVideo extends StatefulWidget {
AspectRatioVideo(this.controller);
final VideoPlayerController controller;
@override
AspectRatioVideoState createState() => AspectRatioVideoState();
}
class AspectRatioVideoState extends State<AspectRatioVideo> {
VideoPlayerController get controller => widget.controller;
bool initialized = false;
void _onVideoControllerUpdate() {
if (!mounted) {
return;
}
if (initialized != controller.value.initialized) {
initialized = controller.value.initialized;
setState(() {});
}
}
@override
void initState() {
super.initState();
controller.addListener(_onVideoControllerUpdate);
}
@override
Widget build(BuildContext context) {
if (initialized) {
return Center(
child: AspectRatio(
aspectRatio: controller.value?.aspectRatio,
child: VideoPlayer(controller),
),
);
} else {
return Container();
}
}
}
static generateImageHash(String fileBytes){
print('fileBytes = $fileBytes');
var bytes = utf8.encode(fileBytes); // data being hashed
String digest = sha256.convert(bytes).toString();
print("This is image Digest : $digest");
return digest;
}
var imageBytes = image.readAsBytesSync().toString();
var result = await compute(generateImageHash, imageBytes);
Future<String> generateImageHash(File file) async{
Digest digest = await sha256.bind(file).openRead()).first;
print("This is image Digest : ${digest.toString()}");
return digest.toString();
}