title: RecyclerView is displayed as a grey box with it's name in the center. Same for an implemented audio Visualizer view
body: <p><a href="https://i.imgur.com/joEzSaw.png" rel="nofollow noreferrer">Here</a> an image to better show the problem I'm having...
  <img src="https://i.imgur.com/joEzSaw.png" alt=""></p>
  
  <p>Around a week ago I implemented a music Viusalizer from <a href="https://github.com/gauravk95/audio-visualizer-android" rel="nofollow noreferrer">here</a>.
  I noticed that it didn't display correctly as it showed up as a grey window (see image above), but thinking that it wasn't a native plugin, I didn't give it too much thought.</p>
  
  <p>Then two days ago I needed to use a RecyclerView, and when I downloaded it, it had the same 'broken' look (see image above). When I saw that, then I knew there was something wrong with the project or Android Studio.</p>
  
  <p>I've already looked to everything I could find on the internet in the past couple of days and I tried everything, from downgrading the sdk compile version, to updating Android Studio to the latest version, to do "Invalidate Cache / Restart" from the 'File' menu.</p>
  
  <p><a href="https://stackoverflow.com/questions/51723986/recyclerview-preview-showing-grey-screen-with-android-support-v7-widget-recycler">this</a>, <a href="https://stackoverflow.com/questions/47049177/instead-of-preview-android-studio-showing-only-black-screen-with-android-act">this</a>, <a href="https://stackoverflow.com/questions/45105932/android-studio-3-constraint-layout-editor-issue">this</a>, <a href="https://stackoverflow.com/questions/45082619/constraint-layout-not-visible-on-the-layout-file-and-getting-the-error-while-i/45094927#45094927">this</a>, <a href="https://stackoverflow.com/questions/51591251/android-studio-textview-not-showing-in-design-view-layout/51591502#51591502">this</a>, <a href="https://stackoverflow.com/questions/47330684/android-studio-layout-design-view-shows-overlay-after-upgrade-to-v3-0">this</a>, <a href="https://stackoverflow.com/questions/52611446/recycleview-displaying-a-grey-area">this</a> and <a href="https://stackoverflow.com/questions/44588343/android-studio-3-constraint-layout-editor-broken/44592153">this</a> are all the things I found and tried, but so far, none helped...</p>
  
  <p>This is my activity java file</p>
  
  <pre><code>package com.franchini.myapplication;
  
  import android.support.v7.app.AppCompatActivity;
  import android.os.Bundle;
  
  public class MainActivity extends AppCompatActivity {
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
      }
  }
  
  </code></pre>
  
  <p>This is my activity xml file</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      tools:context=".MainActivity"&gt;
  
      &lt;com.gauravk.audiovisualizer.visualizer.BlastVisualizer
          xmlns:custom="http://schemas.android.com/apk/res-auto"
          android:id="@+id/blast"
          android:layout_width="0dp"
          android:layout_height="0dp"
          android:layout_marginBottom="16dp"
          custom:avColor="@color/av_dark_blue"
          custom:avDensity="0.8"
          custom:avSpeed="normal"
          custom:avType="fill"
          custom:layout_constraintBottom_toTopOf="@+id/textView"
          custom:layout_constraintEnd_toEndOf="parent"
          custom:layout_constraintStart_toStartOf="parent"
          custom:layout_constraintTop_toTopOf="parent" /&gt;
  
      &lt;TextView
          android:id="@+id/textView"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Hello World!"
          app:layout_constraintBottom_toBottomOf="parent"
          app:layout_constraintLeft_toLeftOf="parent"
          app:layout_constraintRight_toRightOf="parent"
          app:layout_constraintTop_toTopOf="parent" /&gt;
  
      &lt;android.support.v7.widget.RecyclerView
          android:layout_width="0dp"
          android:layout_height="0dp"
          android:layout_marginTop="16dp"
          app:layout_constraintBottom_toBottomOf="parent"
          app:layout_constraintEnd_toEndOf="parent"
          app:layout_constraintHorizontal_bias="0.0"
          app:layout_constraintStart_toStartOf="parent"
          app:layout_constraintTop_toBottomOf="@+id/textView" /&gt;
  
  &lt;/android.support.constraint.ConstraintLayout&gt;
  </code></pre>
  
  <p>This is my styles xml file</p>
  
  <pre><code>&lt;resources&gt;
  
      &lt;!-- Base application theme. --&gt;
      &lt;style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar"&gt;
          &lt;!-- Customize your theme here. --&gt;
          &lt;item name="colorPrimary"&gt;@color/colorPrimary&lt;/item&gt;
          &lt;item name="colorPrimaryDark"&gt;@color/colorPrimaryDark&lt;/item&gt;
          &lt;item name="colorAccent"&gt;@color/colorAccent&lt;/item&gt;
      &lt;/style&gt;
  
  &lt;/resources&gt;
  </code></pre>
  
  <p>This is my build.gradle (project) file</p>
  
  <pre><code>// Top-level build file where you can add configuration options common to all sub-projects/modules.
  
  buildscript {
      repositories {
          google()
          jcenter()
  
      }
      dependencies {
          classpath 'com.android.tools.build:gradle:3.3.2'
  
          // NOTE: Do not place your application dependencies here; they belong
          // in the individual module build.gradle files
      }
  }
  
  allprojects {
      repositories {
          google()
          jcenter()
  
      }
  }
  
  task clean(type: Delete) {
      delete rootProject.buildDir
  }
  </code></pre>
  
  <p>This is my build.gradle (app) file</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  android {
      compileSdkVersion 28
      defaultConfig {
          applicationId "com.franchini.myapplication"
          minSdkVersion 21
          targetSdkVersion 28
          versionCode 1
          versionName "1.0"
          testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
      }
      buildTypes {
          release {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android-optimize.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'
  
      implementation 'com.gauravk.audiovisualizer:audiovisualizer:0.9.1'
  
      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:recyclerview-v7:28.0.0'
  }
  </code></pre>
  
  <p>Now, this problem seems to appear only on the Editor, because when I test it on Android directly, it works like a charm...</p>
  
  <p>Can anyone help me figure this out? Am I missing something really stupid?</p>
  
  <p>[Edit]: I wanted to point out that I get no errors whatsoever with this problem...</p>