无法为 org.gradle.api.Project 类型的根项目 'Socialize' 获取未知 属性 'appCompatVersion'

Could not get unknown property 'appCompatVersion' for root project 'Socialize' of type org.gradle.api.Project

这是我的依赖项build.gradle:app:

implementation "androidx.appcompat:appcompat:$rootProject.appCompatVersion"

implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
api "org.jetbrains.kotlinx:kotlinx-coroutines-core:$rootProject.coroutines"
api "org.jetbrains.kotlinx:kotlinx-coroutines-android:$rootProject.coroutines"

// UI
implementation "androidx.constraintlayout:constraintlayout:$rootProject.constraintLayoutVersion"
implementation "com.google.android.material:material:$rootProject.materialVersion"

/* coroutines support for firebase operations */
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-play-services:1.1.1'


// Import the BoM for the Firebase platform
implementation platform('com.google.firebase:firebase-bom:26.1.0')
implementation 'com.google.firebase:firebase-firestore'
implementation 'com.google.firebase:firebase-auth-ktx'
implementation 'com.firebaseui:firebase-ui-firestore:6.4.0'

implementation 'com.google.android.gms:play-services-auth:19.0.0'

implementation 'com.github.bumptech.glide:glide:4.11.0'
annotationProcessor 'com.github.bumptech.glide:compiler:4.11.0'

// Testing
testImplementation "junit:junit:$rootProject.junitVersion"
androidTestImplementation "androidx.arch.core:core-testing:$rootProject.coreTestingVersion"
androidTestImplementation ("androidx.test.espresso:espresso-core:$rootProject.espressoVersion", {
    exclude group: 'com.android.support', module: 'support-annotations'
})
androidTestImplementation "androidx.test.ext:junit:$rootProject.androidxJunitVersion"

这是 build.gradle:app 的 android 代码:

compileSdkVersion 30
buildToolsVersion "30.0.2"

defaultConfig {
    applicationId "com.example.socialize"
    minSdkVersion 21
    targetSdkVersion 30
    versionCode 1
    versionName "1.0"

    testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}

buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
    }
}

我正在尝试同步 gradle 项目文件,错误是:

Could not get unknown property 'appCompatVersion' for root project 'Socialize' of type 
org.gradle.api.Project.
Open File

当我点击打开文件时,它提示我回到上面列出的第一行依赖文件

我向其中添加了 firebase,还需要添加 Kotlin 协程文件。 我从 here making this app.

粘贴了这段代码

尝试通过将此代码添加到我的 build.gradle

来解决此问题
ext {
appCompatVersion = '1.2.0'
constraintLayoutVersion = '2.0.2'
coreTestingVersion = '2.1.0'
coroutines = '1.3.9'
lifecycleVersion = '2.2.0'
materialVersion = '1.2.1'
// testing
junitVersion = '4.13.1'
espressoVersion = '3.1.0'
androidxJunitVersion = '1.1.2'
}

基本上,这为我们在 build.gradle:app 中使用的实现提供了版本名称,其中我们使用了 $rootProject.appCompatVersion

$rootProject 包含上述代码中定义的版本的变量。