title: Flutter change Slider round Button with an Icon or something else
body: <p>I want to display Icon to set the Slider instead of the round blue default button to set the value.</p>
  <p>My idea looks something like this:</p>
  <p><a href="https://i.stack.imgur.com/M2PhB.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/M2PhB.png" alt="enter image description here" /></a></p>
  <p>Maybe someone can describe me how can i change this button in the middle.
  Thanks for your attantion.</p>