title: BottomSheetDialogFragment is not showing up
body: <p>I've followed <a href="https://medium.com/@kosta.palash/using-bottomsheetdialogfragment-with-material-design-guideline-f9814c39b9fc" rel="noreferrer">this tutorial</a> to implement BottomSheetDiaogFragment in my android application.</p>
  
  <p>this is my bottom sheet layout (bottom_sheet.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"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"&gt;
  
  &lt;RadioGroup
      android:layout_width="0dp"
      android:layout_height="wrap_content"
      android:layout_marginStart="16dp"
      android:layout_marginTop="16dp"
      android:layout_marginEnd="16dp"
      android:layout_marginBottom="16dp"
      app:layout_constraintBottom_toBottomOf="parent"
      app:layout_constraintEnd_toEndOf="parent"
      app:layout_constraintStart_toStartOf="parent"
      app:layout_constraintTop_toTopOf="parent"&gt;
  
      &lt;RadioButton
          android:id="@+id/rb1"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_marginBottom="8dp"
          android:layout_weight="1"
          android:text="@string/rb1" /&gt;
  
      &lt;RadioButton
          android:id="@+id/rb2"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_marginBottom="8dp"
          android:layout_weight="1"
          android:text="@string/rb2" /&gt;
  
  &lt;/RadioGroup&gt;
  &lt;/android.support.constraint.ConstraintLayout&gt;
  </code></pre>
  
  <p>BottomSheetDialogFragment class:</p>
  
  <pre><code>class BottomSheetTaskRepeat : BottomSheetDialogFragment() {
  
      override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
          return inflater.inflate(R.layout.bottom_sheet, container, false)
      }
  }
  </code></pre>
  
  <p>activity:</p>
  
  <pre><code>private val bottomSheetTaskRepeat = BottomSheetTaskRepeat()
  
  override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
  
      bottomSheetTaskRepeat.show(supportFragmentManager, "my_bottom_sheet")
  }
  </code></pre>
  
  <p>The problem is that the bottom sheet is not showing up! Any help is appreciated.</p>