Connection timed out connect. If you are behind an HTTP proxy, please configure the proxy settings either in IDE or Gradle.

当build项目的时候报错：

Connection timed out connect. If you are behind an HTTP proxy, please configure the proxy settings either in IDE or Gradle.

如图：

然后再往下看，报错信息：

A problem occurred configuring root project 'module'.
> Could not resolve all artifacts for configuration ':classpath'.
   > Could not resolve com.android.tools.build:gradle:3.3.2.
     Required by:
         project :
      > Could not resolve com.android.tools.build:gradle:3.3.2.
         > Could not get resource 'https://maven.google.com/com/android/tools/build/gradle/3.3.2/gradle-3.3.2.pom'.
            > Could not HEAD 'https://maven.google.com/com/android/tools/build/gradle/3.3.2/gradle-3.3.2.pom'.
               > Connect to maven.google.com:443 [maven.google.com/172.217.31.238] failed: Connection timed out: connect

如图：

意思是无法获取和编译maven.google资源，通过网上查找相关资料，说是新版的不需要设置代理和*，在build.gradle里面将maven { url “https://maven.google.com” }改为maven {url ‘https://dl.google.com/dl/android/maven2/’}，如下所示（如果已经*需要把*软件关掉，并保证能上网）：

buildscript {
    repositories {
        ... ...
//        maven { url "https://maven.google.com" }
        maven {url 'https://dl.google.com/dl/android/maven2/'}
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.3.2'
    }
}
allprojects {
    repositories {
        ... ...
//        maven { url "https://maven.google.com" }
        maven {url 'https://dl.google.com/dl/android/maven2/'}
    }
    ... ...
}

Android studio右上角点击Sync Now

然后编译成功！