react-native run-android报错: Could not resolve com.android.tools.build:gradle:3.1.4

错误输出

* What went wrong:
A problem occurred configuring root project 'LearnRN'.
> Could not resolve all files for configuration ':classpath'.
   > Could not resolve com.android.tools.build:gradle:3.1.4.
     Required by:
         project :
      > Could not resolve com.android.tools.build:gradle:3.1.4.
         > Could not get resource 'https://dl.google.com/dl/android/maven2/com/android/tools/build/gradle/3.1.4/gradle-3.1.4.pom'.
            > Could not GET 'https://dl.google.com/dl/android/maven2/com/android/tools/build/gradle/3.1.4/gradle-3.1.4.pom'.
               > Connect to dl.google.com:443 [dl.google.com/172.217.25.78] failed: Connection timed out: connect

解决

找了很久, 比较多的是修改build.gradle文件中的maven配置, 但是一直没有效果. 怀疑是网络原因,无法访问到墙外网址.

修改Gradle的Maven仓库地址为国内仓库,例如阿里云

buildscript {
    ext {
        buildToolsVersion = "28.0.3"
        minSdkVersion = 16
        compileSdkVersion = 28
        targetSdkVersion = 26
        supportLibVersion = "27.1.1"
    }
    repositories {
        // google()
        // jcenter()
        maven { url "http://maven.aliyun.com/nexus/content/groups/public/" }
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.2'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

修改buildscript属性下仓库地址

allprojects {
    repositories {
        maven {
            // All of React Native (JS, Obj-C sources, Android binaries) is installed from npm
            url "$rootDir/../node_modules/react-native/android"
            url "$rootDir/../node_modules/react-native/android"
        }
    }
}

这边有个坑的地方， Android文档上说，每个maven仓库链接都应该有自己单独的maven标签。所以上面这种写法是不正确的
需要改为:

allprojects {
    repositories {

        maven {
            // All of React Native (JS, Obj-C sources, Android binaries) is installed from npm
            url "$rootDir/../node_modules/react-native/android"  //打包react native程序时，这个仓库地址是一定要保留的，切记
        }
        maven { 
            url "http://maven.aliyun.com/nexus/content/groups/public/" 
        }
    }
}

Could not find com.android.tools.build:gradle:3.1.4

 Could not resolve all files for configuration ':classpath'.
   > Could not find com.android.tools.build:gradle:3.1.4.
     Searched in the following locations:
         http://maven.aliyun.com/nexus/content/groups/public/com/android/tools/build/gradle/3.1.4/gradle-3.1.4.pom
         http://maven.aliyun.com/nexus/content/groups/public/com/android/tools/build/gradle/3.1.4/gradle-3.1.4.jar
         https://repo.maven.apache.org/maven2/com/android/tools/build/gradle/3.1.4/gradle-3.1.4.pom
         https://repo.maven.apache.org/maven2/com/android/tools/build/gradle/3.1.4/gradle-3.1.4.jar

找到SDK目录中build-tools下自己的版本号,修改android/build:gradle配置文件中的buildToolsVersion属性为自己的版本号,注意compileSdkVersion属性也需要修改,例如版本号为28.0.3 那么compileSdkVersion属性为28