title: How to center a ImageView vertically in its parent?
body: <p>My layout design is a TextView with long text and a ImageView to the right of the TextView. I want to center the ImageView in its parent vertically, so I used android:layout_centerVertical="true", but it turned out that the ImageView was aligned to the bottom of its parent. If I don't use layout_centerVertical property, the ImageView will be aligned to the top of its parent. How can I solve this problem? Thanks.</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  
  &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="fill_parent" android:layout_height="wrap_content"
      android:background="#000000"&gt;
      &lt;ImageView android:id="@+id/t3" android:layout_width="wrap_content"
          android:layout_height="wrap_content" android:src="@drawable/arrow_right"
          android:layout_alignParentRight="true" android:background="#ff0000"
          android:layout_centerVertical="true" android:scaleType="centerInside" /&gt;
      &lt;TextView android:layout_width="fill_parent"
          android:layout_height="wrap_content"
          android:text="This a very very very very very very very very very very very very very very very very long sentence"
          android:textColor="#231ACC" android:layout_toLeftOf="@id/t3" /&gt;
  &lt;/RelativeLayout&gt;
  </code></pre>