无法导入 com.google.android.gms:play-services-ads:17.1.1

apply plugin: 'com.android.application'
   android {
   compileSdkVersion 28

   defaultConfig {
      applicationId "com.kaiboon0216gmail.homeownerstarterkit"
      minSdkVersion 21
      targetSdkVersion 28
      versionCode 1
      versionName "1.0"
      testInstrumentationRunner 
      "android.support.test.runner.AndroidJUnitRunner"
    } 
    buildTypes {
       release {
          minifyEnabled false
          proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
       }
    }
}


dependencies {
   implementation fileTree(dir: 'libs', include: ['*.jar'])
   implementation 'com.android.support:appcompat-v7:28.0.0'
   implementation 'com.android.support.constraint:constraint-layout:1.1.3'
   testImplementation 'junit:junit:4.12'
   androidTestImplementation 'com.android.support.test:runner:1.0.2'
   androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
   implementation 'com.android.support:cardview-v7:28.0.0'
   implementation 'com.google.android.gms:play-services-ads:17.1.1'
}

这些是我的代码.我正在使用 Admob 在我的应用中显示广告.当我添加此代码时:"'com.google.android.gms:play-services-ads:17.1.1'" 和同步，我的应用程序崩溃了.

<meta-data
            android:name="com.google.android.gms.ads.APPLICATION_ID"
            android:value="ca-app-pub-111100000000~1111111"/>