为了方便手机和电脑之间的传输数据，同时考虑下一步局域网内电脑传输方便性，从网上发现了开源软件localsend，该软件是基于flutter开发的，历时大半天才编译成功，记录一下学习过程。
1、localsend软件
LocalSend 是一款免费、开源、跨平台的局域网文件互传工具，无需互联网，无需外部服务器。即开即用，支持 Windows、macOS、Linux，以及 iOS、Android。
LocalSend 在 GitHub 开源，你完全可以自己编译客户端，然后在内网使用。下载地址如下：
GitHub - localsend/localsend: An open-source cross-platform alternative to AirDrop
2、flutter简介
flutter是谷歌的移动UI框架，“只要一套代码库，即可构建、测试和发布适用于移动、Web、桌面和嵌入式平台的精美应用”，从闲鱼到淘宝，从QQ到微信，从京东到百度，从美团到抖音，BAT等一线互联网大厂在全面拥抱Flutter。2020 短短一年里，Flutter在GitHub 和 StackOverflow已经赶超React Native成为开发者首选跨平台框架。
flutter具有以下特性：
- 具有跨平台开发特性，支持IOS、Android、Web三端。
- 热重载特性大大提高了开发效率
- 自绘UI引擎和编译成原生代码的方式，使得系统的运行时的高性能成为了可能
- 使用Dart语言，目前已经支持同时编译成Web端代码
3、搭建flutter开发环境
详见https://flutter.cn/community/china：在中国网络环境下使用 Flutter - Flutter 中文文档 - Flutter 中文开发者网站 - Flutter
在Windows上要安装并运行Flutter要满足以下最低要求:
操作系统: Windows 7 SP1或更新版本
磁盘空间: 400 MB (不包括IDE/tools的磁盘空间）.
工具: Flutter 依赖下面这些命令行工具：
Windows PowerShell 5.0 Windows 10已经预装了这个工具；
Git for Windows 2.x确保Windows电脑下载并安装了Git工具；
以清华镜像为例
3.1设置环境变量
PUB_HOSTED_URL=https://mirrors.tuna.tsinghua.edu.cn/dart-pub
FLUTTER_STORAGE_BASE_URL=https://mirrors.tuna.tsinghua.edu.cn/flutter
3.2下载SDK
Flutter SDK 归档列表 - Flutter 中文文档 - Flutter 中文开发者网站 - Flutter 下载稳定版本SDK，最开始我下载了最新的3.16.3（后来发现给自己挖了一个大坑）。
将安装包zip解压到你想安装Flutter SDK的路径（如：C:\src\flutter；注意，不要将flutter安装到需要一些高权限的路径如C:\Program Files\）。
设置Path环境变量：
3.3获取依赖
利用CMD窗口进入下载好的localsend源程序路径下执行：
E:\Software\localsend-1.13.1\localsend-1.13.1\app>flutter pub get
当配置好环境变量后，手动或自动执行 flutter pub get 后会使用无法正常下载依赖包，时间长了会出现下面的错误Got TLS error trying to find package xxx
解决方案：
利用360浏览器打开Index of /dart-pub/ | 清华大学开源软件镜像站 | Tsinghua Open Source Mirror
右键属性：
导出flutter_pub.der证书文件，然后利用openssl转化成pem文件
E:\flutter>openssl x509 -inform der -in flutter_pub.der -out flutter_pub.pem
说明：https://www.sslshopper.com/certificate-decoder.html可以查看pem文件是否正确，结果如下：
Certificate Information:
Common Name: tuna.tsinghua.edu.cn
Subject Alternative Names: *.tuna.tsinghua.edu.cn, tuna.tsinghua.edu.cn
Organization:
Organization Unit:
Locality:
State:
Country:
Valid From: December 7, 2023
Valid To: March 6, 2024
Issuer: R3, Let's Encrypt
Key Size: 2048 bit
Serial Number: 0360c873c42e84d581f57896df6c2921c5c1
接着配置环境变量
DART_VM_OPTIONS=--root-certs-file=E:\flutter\flutter_pub.pem
再次执行命令，成功下载依赖。
3.4安装VS2022
由于要在windows下编译flutter程序，需要打开系统的开发者模式，执行命令start ms-settings:developers
对于 Windows 桌面开发而言，除了 Flutter SDK 以外你还需要以下内容：
Visual Studio 2022 或 Visual Studio 2022 生成工具 在选择安装 Visual Studio 时或只安装生成工具的时候，你需要选择「使用 C++ 的桌面开发」，包括其所有默认组件，以安装必要的 C++ 工具链和 Windows SDK 的头文件。
下载Visual Studio，下载地址：https://visualstudio.microsoft.com/zh-hans/downloads/
运行安装程序后，选择 使用 C++ 进行桌面开发工作负载，包括其所有默认组件
基本上是说，如果您想为 Windows 开发 Flutter 应用程序，则需要安装Visual Studio 2022，在安装 Visual Studio 2022 时，您需要下载：Desktop development with C++
3.5 flutter doctor检查
运行flutter doctor检查
E:\flutter>flutter doctor
Flutter assets will be downloaded from https://mirrors.tuna.tsinghua.edu.cn/flutter. Make sure you trust this source!
Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 3.13.9, on Microsoft Windows [版本 10.0.19045.3693], locale zh-CN)
[√] Windows Version (Installed version of Windows is version 10 or higher)
[X] Android toolchain - develop for Android devices
X Unable to locate Android SDK.
Install Android Studio from: https://developer.android.com/studio/index.html
On first launch it will assist you in installing the Android SDK components.
(or visit https://flutter.dev/docs/get-started/install/windows#android-setup for detailed instructions).
If the Android SDK has been installed to a custom location, please use
`flutter config --android-sdk` to update to that location.
[X] Chrome - develop for the web (Cannot find Chrome executable at .\Google\Chrome\Application\chrome.exe)
! Cannot find Chrome. Try setting CHROME_EXECUTABLE to a Chrome executable.
[√] Visual Studio - develop Windows apps (Visual Studio Community 2022 17.8.3)
[!] Android Studio (not installed)
[√] Connected device (2 available)
[√] Network resources
! Doctor found issues in 3 categories.
此时就完成了flutter环境的构建。
4、localsend软件编译
在E:\Software\localsend-1.13.1\localsend-1.13.1\app路径下执行：
flutter build windows
最开始由于我下载的3.16.3版本的flutter，编译报错：
/C:/Users/Administrator/AppData/Local/Pub/Cache/hosted/mirrors.tuna.tsinghua.edu.cn%2547dart-pub%2547/photo_manager-2.8.1/lib/src/internal/image_provider.dart(71,5): error G5FE39F1E: Type 'DecoderCallback' not found. [E:\Software\localsend-1.13.1\localsend-1.13.1\app\build\windows\x64\flutter\flutter_assemble.vcxproj]
/C:/Users/Administrator/AppData/Local/Pub/Cache/hosted/mirrors.tuna.tsinghua.edu.cn%2547dart-pub%2547/photo_manager-2.8.1/lib/src/internal/image_provider.dart(96,5): error G5FE39F1E: Type 'DecoderCallback' not found. [E:\Software\localsend-1.13.1\localsend-1.13.1\app\build\windows\x64\flutter\flutter_assemble.vcxproj]
/C:/Users/Administrator/AppData/Local/Pub/Cache/hosted/mirrors.tuna.tsinghua.edu.cn%2547dart-pub%2547/photo_manager-2.8.1/lib/src/internal/image_provider.dart(71,5): error G93EAFBA7: 'DecoderCallback' isn't a type. [E:\Software\localsend-1.13.1\localsend-1.13.1\app\build\windows\x64\flutter\flutter_assemble.vcxproj]
/C:/Users/Administrator/AppData/Local/Pub/Cache/hosted/mirrors.tuna.tsinghua.edu.cn%2547dart-pub%2547/photo_manager-2.8.1/lib/src/internal/image_provider.dart(96,5): error G93EAFBA7: 'DecoderCallback' isn't a type. [E:\Software\localsend-1.13.1\localsend-1.13.1\app\build\windows\x64\flutter\flutter_assemble.vcxproj]
e:\Program Files\Microsoft Visual Studio\2022\Community\MSBuild\Microsoft\VC\v170\Microsoft.CppCommon.targets(254,5): error MSB8066: E:\Software\localsend-1.13.1\localsend-1.13.1\app\build\windows\x64\CMakeFiles\3e2763436f533117eea22937f39400f3\flutter_windows.dll.rule;E:\Software\localsend-1.13.1\localsend-1.13.1\app\build\windows\x64\CMakeFiles\2a8a145387b0dca97778dabe97f93418\flutter_assemble.rule; [E:\Software\localsend-1.13.1\localsend-1.13.1\app\build\windows\x64\flutter\flutter_assemble.vcxproj]
耽误了很多时间，重新下载3.13.9版本的flutter解决问题。
E:\Software\localsend-1.13.1\localsend-1.13.1\app>flutter build windows
Flutter assets will be downloaded from https://mirrors.tuna.tsinghua.edu.cn/flutter. Make sure you trust this source!
Building Windows application... 126.7s
√ Built build\windows\runner\Release\localsend_app.exe (0.2MB).