title: Animating fragments transition
body: <p>I've implemented a layout like this:</p>
  
  <p><img src="https://i.stack.imgur.com/OsysI.png" alt="enter image description here"></p>
  
  <p>whit this configuration:</p>
  
  <pre><code>Fragment A: weight 1
  Fragment B: weight 3
  </code></pre>
  
  <p>Now I want that a third fragment (Fragment C) is added in my layout, as shown in the below image:</p>
  
  <p><img src="https://i.stack.imgur.com/Wiw2m.jpg" alt="enter image description here"></p>
  
  <p>I would that the width of screen is divided in this way:</p>
  
  <pre><code>Fragment A: weight 1
  Fragment B: weight 2
  Fragment C: weight 1
  </code></pre>
  
  <p>So that the Fragment B loses a portion of his width, while the width of Fragment A remains the same.</p>
  
  <p>I want also that this operation is made with an animation. While the fragment B is appearing the fragment C loses portion of his width.</p>
  
  <p>How can I achieve this?</p>