title: app setBackground() error: incompatible types: int cannot be converted to Drawable
body: <p>Working on a very simple app to change color of background upon clicking a button, I am stuck at a bug where the color of background is unable to be changed using MainActivity.java file.</p>
  
  <pre><code>package com.example.audio;
  
  import android.support.v7.app.AppCompatActivity;
  import android.os.Bundle;
  import android.view.View;
  
  public class MainActivity extends AppCompatActivity {
      View view;
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
          view = this.getWindow().getDecorView();
          view.setBackground(R.color.colorAccent);
      }
  }
  </code></pre>
  
  <p>colors.xml</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;resources&gt;
      &lt;color name="colorPrimary"&gt;#008577&lt;/color&gt;
      &lt;color name="colorPrimaryDark"&gt;#00574B&lt;/color&gt;
      &lt;color name="colorAccent"&gt;#D81B60&lt;/color&gt;
  &lt;/resources&gt;
  </code></pre>
  
  <p>activity_main.xml</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;Button
          android:id="@+id/button"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_marginStart="8dp"
          android:layout_marginLeft="8dp"
          android:layout_marginTop="8dp"
          android:layout_marginEnd="8dp"
          android:layout_marginRight="8dp"
          android:layout_marginBottom="8dp"
          android:text="Button"
          app:layout_constraintBottom_toBottomOf="parent"
          app:layout_constraintEnd_toEndOf="parent"
          app:layout_constraintStart_toStartOf="parent"
          app:layout_constraintTop_toTopOf="parent" /&gt;
  &lt;/android.support.constraint.ConstraintLayout&gt;
  </code></pre>
  
  <p>When setting the background in MainActivity.java file, the following error pops up for the line view.setBackground(R.color.colorAccent);</p>
  
  <p>error: incompatible types: int cannot be converted to Drawable</p>
  
  <p>What should I do to resolve this bug?</p>