title: How to overlay views in other apps
body: <p>Where do I start?</p>
  
  <p>I don't know what functions or permissions will I use to make this.
  No root required.</p>
  
  <p>The view look like this, the camera button on the right side, it is floating and visible to other apps, if you push it, it will capture a screenshot.</p>
  
  <p><img src="https://i.stack.imgur.com/V1VQA.jpg" alt="enter image description here"></p>
  
  <p>Note: I will not make make a screenshot app, this is only an example of what I want to achieve.</p>