错误:包Rx.ANDROID.调度程序不存在

这是我的毕业档案

主梯度文件

buildscript {

    repositories {
        jcenter()
        google()
        maven { url 'http://repo1.maven.org/maven2' }
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.3.2'
        classpath "com.fernandocejas.frodo:frodo-plugin:0.8.1"
        classpath 'com.frogermcs.androiddevmetrics:androiddevmetrics-plugin:0.4'
        classpath 'com.google.gms:google-services:4.2.0'
    }
} 

allprojects {
    repositories {
        jcenter()
    }
}
repositories {
    maven { url 'http://repo1.maven.org/maven2' }
    jcenter()
}

应用程序渐变文件

compileSdkVersion 28
    buildToolsVersion '28.0.3'

   defaultConfig {
        applicationId "com.xxx.xxx"
        minSdkVersion 21
        targetSdkVersion 27
        versionCode 187
        versionName "1.0.5"
        multiDexEnabled true
        vectorDrawables.useSupportLibrary = true
    }

dependencies {
  implementation 'io.reactivex.rxjava2:rxandroid:2.1.1'
    implementation 'io.reactivex.rxjava2:rxjava:2.2.7'
implementation group: 'com.squareup.retrofit2', name: 'adapter-rxjava2', version: '2.2.0'
    implementation 'com.android.support:multidex:1.0.2'
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support:support-v13:28.0.0'
    implementation 'com.android.support:appcompat-v7:28.0.0'
implementation 'com.android.support:design:28.0.0'
    implementation 'com.android.support:cardview-v7:28.0.0'
    implementation 'com.android.support:recyclerview-v7:28.0.0'

   implementation 'com.squareup.retrofit2:retrofit:2.1.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.1.0'
    implementation 'com.squareup.retrofit2:adapter-rxjava:2.1.0'

}

我的示例用法

//Here is the error

import io.reactivex.android.schedulers.AndroidSchedulers;
compositeSubscription.add(publishRelay.asObservable().observeOn(AndroidSchedulers.mainThread()).subscribe(iView -> {

    }

我在网上看了一眼,但什么都不管用。

有人能告诉我可能出了什么问题吗。

右