无法导入任何Firebase类

Question

突然之间，我突然无法导入或使用任何Firebase类。类名显示在intellisense中，但是当按Tab键导入时，它会插入完全限定名，并在类名中输入错误。

build.gradle（app）

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 'android-P'
    defaultConfig {
        applicationId "com.opticalgenesis.lbp.dogg"
        minSdkVersion 21
        targetSdkVersion 'P'
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'androidx.appcompat:appcompat:1.0.0-alpha1'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.0'
    implementation 'com.google.firebase:firebase-core:16.0.0'
    implementation 'com.google.firebase:firebase-ml-model-interpreter:16.0.0'
    implementation 'com.google.android.material:material:1.0.0-alpha1'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.1.0-alpha3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.0-alpha3'
}

apply plugin: 'com.google.gms.google-services'

build.gradle（项目）

buildscript {
    ext.kotlin_version = '1.2.41'
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.2.0-alpha16'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath 'com.google.gms:google-services:4.0.1'

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

allprojects {
    repositories {
        google()
        jcenter()
        maven {
            url="https://maven.google.com"
        }
    }
}

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

小片段

 private fun setupModel() {
        val builder = com.google.firebase.ml.custom.model.FirebaseModelDownloadConditions.Builder()
    }

FirebaseModelDownloadConditions并不是唯一没有导入的类，它们都没有。

感谢任何帮助。

感谢。