flutter A problem occurred configuring root project 'fluttertoast'.

flutter打包Android的release包的时候报错，由于之前升级过flutter版本，打包的这个工程又是升级之前创建的，然后在执行flutter build apk的时候报错

* What went wrong:
A problem occurred configuring root project 'fluttertoast'.
> SDK location not found. Define location with sdk.dir in the local.properties file or with an ANDROID_HOME environment variable.

很难受，这种关于安卓配置的问题报错，有点让人摸不着头脑，各种百度，各种谷歌搜索，都没有能好到比较好的解决方案，可是包还是要打啊，要不然，不是白开发了，于是创建了一个更新后的flutter工程，比较了一下build.gradle这个文件，发现里面版本号是有差异的，
更新对应version到最新

    ext.kotlin_version = '1.3.50'
    dependencies {
        classpath 'com.android.tools.build:gradle:3.5.0'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }

如果出现 Minimum supported Gradle version

   > Minimum supported Gradle version is 5.4.1. Current version is 4.4.1. If using the gradle wrapper, try editing the distributionUrl in /Users/chenhao/tiny/Git/flutter/xxs/android/gradle/wrapper/gradle-wrapper.properties to gradle-5.4.1-all.zip

出现上述问题，则需要找到 android/gradle/wrapper/gradle-wrapper.properties这个文件,并且把distributionUrl更新成 distributionUrl=https://services.gradle.org/distributions/gradle-5.4.1-all.zip
gradle-5.4.1-all.zip上面提示对应的名字

如果卡在Running Gradle task 'assembleRelease'... 可以修改

      // google()
        // jcenter()
        maven{ url 'https://maven.aliyun.com/repository/google' }
        maven{ url 'https://maven.aliyun.com/repository/jcenter' }
        maven{url 'http://maven.aliyun.com/nexus/content/groups/public'}

执行 flutter build apk

Running Gradle task 'assembleRelease'...                                
Running Gradle task 'assembleRelease'... Done                       9.2s
✓ Built build/app/outputs/apk/release/app-release.apk (21.4MB).

备忘

export PATH=/Users/chenhao/flutter/bin:$PATH
export PATH=/usr/local/opt/openssl/bin:$PATH
export PATH=/usr/local/opt/libxml2/bin:$PATH
export PATH="$PATH":"$HOME/flutter/.pub-cache/bin"

export DART_HOME=/Users/chenhao/flutter/bin/cache/dart-sdk/bin
export PATH=${DART_HOME}:${PATH}

export PATH="$PATH":"$HOME/.pub-cache/bin"

export PUB_HOSTED_URL=https://pub.flutter-io.cn
export FLUTTER_STORAGE_BASE_URL=https://storage.flutter-io.cn

问题解决，处理这个问题，花费了好几个小时，由于之前主要从事iOS相关app开发，对应安卓上面遇到的问题，会比较懵逼，好在功夫不负有心人，总算解决了，这里记录下，希望以后再遇到类似的可以回去查看