Could not download rxjava.jar (io.reactivex.rxjava2:rxjava:2.2.3)

 (1)在gradle里面buildscript加上这句

allprojects {
    repositories {
        mavenCentral()
        google()
        jcenter()

        maven { url "https://jitpack.io" }
        maven { url 'https://maven.google.com' }
        maven {
            url 'https://oss.sonatype.org/content/repositories/snapshots'
        }
       
    }
}

(2)同一个文件gradle下面有添加 mavenCentral()

allprojects {
    repositories {
        mavenCentral()
        google()
        jcenter()
      
    }
}