当我放入admob依赖项时如何修复Gradle依赖项

Question

当我将Google AdMob依赖项com.google.android.gms:play-services-ads:18.1.1放在Gradle文件中时， com.android.support:appcompat-v7:28.0.0中的错误。那么我该如何解决呢？ 请帮帮我。这是该错误的屏幕截图。

build.gradle具有以下依赖性。

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support:design:28.0.0'
    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:recyclerview-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    implementation 'com.facebook.fresco:fresco:1.13.0'
    implementation 'com.facebook.fresco:webpsupport:1.13.0'
    implementation 'com.facebook.fresco:animated-webp:1.13.0'
    implementation 'com.facebook.fresco:animated-base:1.13.0'

    implementation 'com.google.android.gms:play-services-ads:18.1.1'
}