title: Constraint Layout Getting a default top margin for imageview
body: <p>I am trying to create a layout using constraint layout, with an ImageView on top, a button in the ImageView, a TextView below it and then another TextView below it. Following is the xml:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;android.support.v7.widget.CardView
      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"
      android:layout_margin="10dp"
      app:cardElevation="4dp"&gt;
      &lt;RelativeLayout
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:background="@android:color/white"&gt;
          &lt;android.support.constraint.ConstraintLayout
              android:layout_width="match_parent"
              android:layout_height="wrap_content"&gt;
              &lt;ImageView
                  android:id="@+id/news_image1"
                  android:layout_width="0dp"
                  android:layout_height="0dp"
                  app:layout_constraintDimensionRatio="16:9"
                  android:scaleType="centerCrop"
                  android:adjustViewBounds="true"
                  app:layout_constraintTop_toTopOf="parent"
                  android:layout_marginTop="0dp"
                  app:layout_constraintRight_toRightOf="parent"
                  app:layout_constraintLeft_toLeftOf="parent"
                  app:layout_constraintBottom_toTopOf="@+id/news_title1"/&gt;
              &lt;ImageButton
                  android:id="@+id/news_share_button_1"
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
                  android:background="@android:color/transparent"
                  android:src="@drawable/share_button_big"
                  app:layout_constraintBottom_toBottomOf="@+id/news_image1"
                  app:layout_constraintRight_toRightOf="@+id/news_image1"
                  android:layout_marginRight="15dp"
                  android:layout_marginEnd="15dp"/&gt;
              &lt;TextView
                  android:id="@+id/news_title1"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  android:layout_centerHorizontal="true"
                  android:gravity="center_vertical|start"
                  android:layout_alignParentBottom="true"
                  android:lines="3"
                  android:ellipsize="end"
                  app:layout_constraintTop_toBottomOf="@+id/news_image1"
                  app:layout_constraintBottom_toTopOf="@+id/news_read_more1"
                  app:layout_constraintLeft_toLeftOf="parent"
                  app:layout_constraintRight_toRightOf="parent"
                  android:textColor="@color/colorPrimaryText"
                  android:layout_margin="@dimen/news_cell0_textview_margin"
                  android:textSize="12sp"
                  android:typeface="monospace" /&gt;
              &lt;TextView
                  android:id="@+id/news_read_more1"
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
                  android:layout_centerHorizontal="true"
                  android:gravity="center_vertical|start"
                  android:layout_alignParentBottom="true"
                  android:lines="1"
                  android:ellipsize="end"
                  app:layout_constraintTop_toBottomOf="@+id/news_title1"
                  app:layout_constraintBottom_toBottomOf="parent"
                  app:layout_constraintLeft_toLeftOf="parent"
                  android:textColor="@color/read_more_text_color"
                  android:text="@string/news_read_more"
                  android:layout_margin="@dimen/news_cell0_textview_margin"
                  android:textSize="10sp" /&gt;
          &lt;/android.support.constraint.ConstraintLayout&gt;
      &lt;/RelativeLayout&gt;
  &lt;/android.support.v7.widget.CardView&gt;
  </code></pre>
  
  <p>Everything is correct except for a small margin on top of the first ImageView. Whatever I do I cannot get rid of that margin. See the image below.</p>
  
  <p><a href="https://i.stack.imgur.com/qdMV9.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qdMV9.jpg" alt="enter image description here"></a></p>
  
  <p>Please note the margin between the top of the ImageView and the card, that is what is troubling me.</p>