title: Custom view and change the size of the child views
body: <p>I have a custom view that extends from FrameLayout. I'd like one of the children to have a size equal to the 20% of the total size as shown in the image.</p>
  
  <p>How can I achieve the imageview to always have this size even if the custom view changes its size in runtime?</p>
  
  <p><img src="https://i.stack.imgur.com/Niabn.png" alt="enter image description here"></p>