记一次升级Flutter SDK失败的光辉历史
提示：本文内容颇为复杂，涉及到的疑难杂症也颇多。
一切源于一个简单的指令：flutter upgrade，然后开启了崩溃的黑色3小时。
刚打开项目，看到控制台的编译log提示Flutter SDK可以更新，行吧，那就更新吧，想着应该也是一个很简单的事情，因为我Android Studio也是经常更新的。
ok，编译结束，Terminal中直接执行flutter upgrade，因为之前也在官方文档中看到过升级 Flutter的介绍，内容不多，以为不复杂呢，结果这一执行直接掉进了无底的深渊。。
对插件下手
执行之后显示如下：
D:\FlutterProjects\wanandroid_flutter>flutter upgrade
Checking Dart SDK version...
Downloading Dart SDK from Flutter engine 52c7a1e849a170be4b2b2fe34142ca2c0a6fea1f...
Downloading the Dart SDK using the BITS service failed, retrying with WebRequest...
Invoke-WebRequest : 请求被中止: 未能创建 SSL/TLS 安全通道。
所在位置 D:\flutter\flutter_windows_v1.2.1-stable\flutter\bin\internal\update_dart_sdk.ps1:62 字符: 5
+ Invoke-WebRequest -Uri $dartSdkUrl -OutFile $dartSdkZip
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-WebRequest]，WebException
+ FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeWebRequestCommand
Error: Unable to update Dart SDK. Retrying...
网上搜了一会，根本没结果，但是我此刻也依然没当回事，并开启了一些骚操作。。
上面看到要升级Dart的sdk，因为dart的sdk是包含在flutter中的，在as在装flutter插件的时候还提示要装dart插件，
所以我直接从插件plugin下手了。
- 卸载dart插件然后重启，卸载flutter插件然后重启。
- 安装dart插件然后重启，安装flutter插件然后重启。
但是编译还是跑不起来，报什么错忘了，继续骚操作。。
对SDK下手
既然插件不行，行吧，那就直接手动升级sdk吧，此刻心态依然乐观，说来也是心大。
然后跑去github看了一下版本
纳尼，一天一个版本？？？ 这也太假了吧，我只要正式版就行啊。
然后又跑去官网看看：
嗯，这还差不多，我上个版本就是 1.2.1的，最新1.5.4的，那行吧，下载下来
- 解压
- 删掉1.2.1的版本
- 改环境变量
- 重启AS
emmmm 还是不行，且文件全部报错，开始有一点慌了。。
然后想起来项目中的路径可能还没改呢，然后在设置中把flutter sdk路径改成1.5.4的，感觉应该可以了
改好之后，满怀着期待重新编译，依然不行，此刻心态已经有点崩了，现在是退不能退 进不能进了。
尝试一下invalidate and restart，emmm 也不行
报错如下：
Warning! This package referenced a Flutter repository via the .packages file that is no longer available. The repository from which the 'flutter' tool is currently executing will be used instead.
running Flutter tool: D:\flutter\flutter_windows_v1.5.4-hotfix.2-stable\flutter
previous reference : D:\flutter\flutter_windows_v1.2.1-stable\flutter
This can happen if you deleted or moved your copy of the Flutter repository, or if it was on a volume that is no longer mounted or has been mounted at a different location. Please check your system path to verify that you are running the expected version (run 'flutter --version' to see which flutter is on your path).
嗯，我也知道两次版本不对，可是在哪改、怎么改呢。
对项目配置下手
我开始在项目中找有没有编译时类似build产生的文件，最后在根目录的.package文件中发现还是1.2.1的版本的
# Generated by pub on 2019-05-28 10:50:34.749388.
async:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/async-2.0.8/lib/
boolean_selector:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/boolean_selector-1.0.4/lib/
charcode:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/charcode-1.1.2/lib/
collection:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/collection-1.14.11/lib/
cookie_jar:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/cookie_jar-1.0.0/lib/
cupertino_icons:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/cupertino_icons-0.1.2/lib/
dio:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/dio-2.1.3/lib/
flutter:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/packages/flutter/lib/
flutter_page_indicator:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/flutter_page_indicator-0.0.3/lib/
flutter_swiper:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/flutter_swiper-1.1.6/lib/
flutter_test:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/packages/flutter_test/lib/
flutter_webview_plugin:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/flutter_webview_plugin-0.3.5/lib/
fluttertoast:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/fluttertoast-3.0.4/lib/
matcher:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/matcher-0.12.3+1/lib/
meta:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/meta-1.1.6/lib/
path:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/path-1.6.2/lib/
pedantic:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/pedantic-1.4.0/lib/
quiver:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/quiver-2.0.1/lib/
sky_engine:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/bin/cache/pkg/sky_engine/lib/
source_span:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/source_span-1.5.4/lib/
stack_trace:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/stack_trace-1.9.3/lib/
stream_channel:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/stream_channel-1.6.8/lib/
string_scanner:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/string_scanner-1.0.4/lib/
term_glyph:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/term_glyph-1.1.0/lib/
test_api:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/test_api-0.2.2/lib/
transformer_page_view:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/transformer_page_view-0.1.6/lib/
typed_data:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/typed_data-1.1.6/lib/
vector_math:file:///D:/flutter/flutter_windows_v1.2.1-stable/flutter/.pub-cache/hosted/dart-pub.mirrors.sjtug.sjtu.edu.cn%2547/vector_math-2.0.8/lib/
wanandroid_flutter:lib/
文件备份一下然后直接删掉，看看会不会编译生成，结果没有
那行吧，直接把路径替换了
天呐，依然不行，搞这个的时间早都超出预算了，心态已经崩了，只能硬着头皮上了。
只能在项目设置中尝试了。
打开Project Structure，果然他丫的还是有问题，但是看到了黎明的曙光。
- 1，还是上面的问题。
- 2，果然还是有一个路径没有改
- 3，kotlin的直接忽略
先改掉2的路径问题
把1.2.1的版本路径换成1.5.4的路径即可。
但是1要fix的话提示我全部移除，那行吧，试试。
编译一下还是不行，此刻已然是生无可恋了。
因为之前打开了pubspec.yaml文件查看是不是有配置什么的没改，然后随手点了下packages get，结果OK了！！！
复盘
因为是手动升级的flutter SDK，所以项目中除了自带的库以外还有第三方的库，都还是原来的路径，在把全部路径修改完之后，需要packages get 重新下载到新版本的路径中去才能引用。
之前也尝试过packages upgrade，但是等了半天没反应，也没在任务管理中看到下载，所以就没当回事。。
这种小事就不提了。。
期间也遇到
Waiting for another flutter command to release the startup lock...
解决办法：
- 打开任务管理器，结束掉
Android Studio和Dart.exe - 删除
flutter\bin\cache目录下的lockfile文件，然后重启AS即可
本文旨为flutter upgrade 升级flutter失败之后手动升级的记录，没准你一下就成功了。。
心累。。
Flutter 环境配置：https://blog.csdn.net/yechaoa/article/details/89150852
官方文档：https://flutter.dev/