啓動 flutter項目時報Could not find com.android.tools.build:gradle:3.2.1.

Error running Gradle:
ProcessException: Process "D:\Android\APP path\flutter_app2\flutter_app2\android\gradlew.bat" exited abnormally:

> Configure project :app

Project evaluation failed including an error in afterEvaluate {}. Run with --stacktrace for details of the afterEvaluate {} error.

FAILURE: Build failed with an exception.

* Where:
Build file 'D:\Android\APP path\flutter_app2\flutter_app2\android\app\build.gradle' line: 25

* What went wrong:
A problem occurred evaluating project ':app'.
> Could not resolve all artifacts for configuration 'classpath'.
   > Could not find com.android.tools.build:gradle:3.2.1.
     Searched in the following locations:
       - https://maven.aliyun.com/repository/jcenter/com/android/tools/build/gradle/3.2.1/gradle-3.2.1.pom
       - https://maven.aliyun.com/repository/jcenter/com/android/tools/build/gradle/3.2.1/gradle-3.2.1.jar
       - http://maven.aliyun.com/nexus/content/groups/public/com/android/tools/build/gradle/3.2.1/gradle-3.2.1.pom
       - http://maven.aliyun.com/nexus/content/groups/public/com/android/tools/build/gradle/3.2.1/gradle-3.2.1.jar
     Required by:
         unspecified:unspecified:unspecified

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full
insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 3s
Picked up _JAVA_OPTIONS: -Djava.NET.preferIPv4Stack=true
  Command: D:\Android\APP path\flutter_app2\flutter_app2\android\gradlew.bat app:properties

Please review your Gradle project setup in the android/ folder.

大致意思是說：運行Gradle時出錯，導致構建flutter構建失敗

原因是因爲獲取不到 com.android.tools.build:gradle:3.2.1

原因一：

獲取不到的原因一般是因爲在中國沒辦法訪問谷歌資源（有外網，翻牆等的除外），此時的解決辦法是 改用阿里的鏡像。

分兩步：

• 第一步：修改掉項目下的 android目錄下的 build.gradle 文件，把 google() 和 jcenter()這兩行去掉。
  並在下面添加阿里的鏈接 （注意：有兩處修改）

  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' }
  

  如下：

  buildscript {
      repositories {
  //        google()
  //        jcenter()
  		// 添加
          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' }
      }
  
      dependencies {
          classpath 'com.android.tools.build:gradle:3.2.1'
      }
  }
  
  allprojects {
      repositories {
  //        google()
  //        jcenter()
  //        maven {
  //            url 'https://google.bintray.com/exoplayer/'
  //        }
  		// 添加
          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' }
      }
  }
  
  rootProject.buildDir = '../build'
  subprojects {
      project.buildDir = "${rootProject.buildDir}/${project.name}"
  }
  subprojects {
      project.evaluationDependsOn(':app')
  }
  
  task clean(type: Delete) {
      delete rootProject.buildDir
  }
  
  

• 第二步：修改 Flutter SDK 包下的 flutter.gradle 文件
  路徑根據你的sdk存放位置，例如我的是D:\SDK\Flutter\packages\flutter_tools\gradle\flutter.gradle
  同樣將 google()和 jcenter() 修改爲阿里的鏈接

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

  如下：

  buildscript {
      repositories {
          //google()
          //jcenter()
          // 添加
  		maven { url 'https://maven.aliyun.com/repository/jcenter' }
  		maven { url 'http://maven.aliyun.com/nexus/content/groups/public' }
      }
      dependencies {
          classpath 'com.android.tools.build:gradle:3.2.1'
      }
  }
  

至此，在國內沒辦法訪問谷歌資源的問題就解決了

然而，我的問題並沒解決

仔細看報錯信息後，發現找不到以下資源地址

    -  https://maven.aliyun.com/repository/jcenter/com/android/tools/build/gradle/3.2.1/gradle-3.2.1.pom
    -  https://maven.aliyun.com/repository/jcenter/com/android/tools/build/gradle/3.2.1/gradle-3.2.1.jar
    -  http://maven.aliyun.com/nexus/content/groups/public/com/android/tools/build/gradle/3.2.1/gradle-3.2.1.pom
    -  http://maven.aliyun.com/nexus/content/groups/public/com/android/tools/build/gradle/3.2.1/gradle-3.2.1.jar

看到這裏說明阿里鏈接是配置上了的，之所以找不到是因爲gradle-3.2.1這個3.2.1版本太高了，應該是最新的

阿里連接中的gradle最高版本好像才3.1.2，所以獲取不到

所以，解決辦法是將項目下的android目錄下的build.gradle文件和flutter SDK包下的flutter.gradle文件中的gradle版本改爲阿里鏡像中存在的版本

	dependencies {
        classpath 'com.android.tools.build:gradle:3.1.2'
    }

來自於 https://blog.csdn.net/qq_33684444/article/details/86656301