flutter A problem occurred configuring root project 'fluttertoast'.

flutter打包Android的release包的時候報錯，由於之前升級過flutter版本，打包的這個工程又是升級之前創建的，然后在執行flutter build apk的時候報錯

* 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.

很難受，這種關於安卓配置的問題報錯，有點讓人摸不着頭腦，各種百度，各種谷歌搜索，都沒有能好到比較好的解決方案，可是包還是要打啊，要不然，不是白開發了，於是創建了一個更新后的flutter工程，比較了一下build.gradle這個文件，發現里面版本號是有差異的，
更新對應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"
    }

如果出現 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

出現上述問題，則需要找到 android/gradle/wrapper/gradle-wrapper.properties這個文件,並且把distributionUrl更新成 distributionUrl=https\://services.gradle.org/distributions/gradle-5.4.1-all.zip
gradle-5.4.1-all.zip上面提示對應的名字

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'}

執行 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).

備忘

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

問題解決，處理這個問題，花費了好幾個小時，由於之前主要從事iOS相關app開發，對應安卓上面遇到的問題，會比較懵逼，好在功夫不負有心人，總算解決了，這里記錄下，希望以后再遇到類似的可以回去查看