1.操作步骤

在项目根目录下，用 cmd 或者 powershell 运行：

.\android\gradlew
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会输出以下内容：

Starting a Gradle Daemon, 1 incompatible and 2 stopped Daemons could not be reused, use --status for details

> Task :help

Welcome to Gradle 4.10.2.

To run a build, run gradlew <task> ...

To see a list of available tasks, run gradlew tasks

To see a list of command-line options, run gradlew --help

To see more detail about a task, run gradlew help --task <task>

For troubleshooting, visit https://help.gradle.org

BUILD SUCCESSFUL in 3s
actionable task: 1 executed
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然后再重新运行项目即可。

2.经过上面的步骤之后，如果还是不行，则是因为墙的问题了

打开 项目目录/android/build.gradle，替换成阿里的源：

buildscript {
    repositories {
         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' }
//       google()        
//       jcenter()        
    }

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

allprojects {
    repositories {
        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' }
//        google()
//        jcenter()
    }
}

rootProject.buildDir = '../build'
subprojects {
    project.buildDir = "${rootProject.buildDir}/${project.name}"
}
subprojects {
    project.evaluationDependsOn(':app')
}

task clean(type: Delete) {
    delete rootProject.buildDir
}
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