title: RecyclerView cannot be found
body: <p>I just started to try to use the RecyclerView. I added some lines into the build.grandle but I always get many error messages telling me:
  ' error: cannot find symbol'
  ' error: package androidx.recyclerview.widget does not exist'
  and I do not understand why I am getting these error messages. Here you see the code of my grandle:</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  android {
      compileSdkVersion 27
      defaultConfig {
          applicationId "com.example.td.barapp"
          minSdkVersion 15
          targetSdkVersion 27
          versionCode 1
          versionName "1.0"
          testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
          viewBinding {
              enabled = true
          }
  
      }
      buildTypes {
          release {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
          }
      }
  }
  
  dependencies {
      implementation fileTree(dir: 'libs', include: ['*.jar'])
      implementation 'com.android.support:appcompat-v7:27.1.1'
      implementation 'com.android.support.constraint:constraint-layout:1.1.3'
      implementation 'com.android.support:design:27.1.1'
      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:support-v4:27.1.1'
      implementation 'com.android.support:recyclerview-v7:27.0.0'
      implementation 'com.android.support:cardview-v7:27.0.0'
  }
  </code></pre>
  
  <p>I'd appreciate every comment and would be quite thankful. </p>
  
  <p>Update: I think I have a problem with AndroidX. I migrated to it by using Refactor-->Migrate to AndroidX in Android studio but I do not know how I should change my posted grandle.build file. At the moment in my grandle file I have some libararies like " implementation 'com.android.support:design:27.1.1' and I get the warning and error message: "This support library should not use a different version (27) than the compileSdkVersion (28) " But when I use " implementation 'com.android.support:appcompat-v7:28.0'" I also get an error message :"All com.android.support libraries must use the exact same version specification (mixing versions can lead to runtime crashes). Found versions 27.1.1, 27.0.0. Examples include com.android.support:animated-vector-drawable..</p>
  
  <p>Here you see a screenshot of the marked lines in the Build grandle file:<a href="https://i.stack.imgur.com/rzOLt.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rzOLt.png" alt="Screenshot Android Studio of the build grandle file"></a> How do I have to change these lines in order to use AndroidX? I'd be happy for your help because I am stuck on that problem. </p>