title: Requires API level 21 (current min is 16)
body: <p>I'm new in android development and programming. I'm working on android camera application. I'm new in this so I use the lectures of a youtuber who uses API level 21 and I'm using API level 16 for maximum users but our code is same which causes a problem. </p>
  
  <p><a href="https://i.stack.imgur.com/lLHFy.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/lLHFy.png" alt="enter image description here"></a></p>
  
  <p>call requires API level 21 (current min is <code>16):android.hardware.camera2.CameraDevice.StateCallback#StateCallback</code> more...<kbd>CTRL</kbd> + <kbd>f1</kbd>)</p>
  
  <p>Please help me to fix this. I don't want to change its API level to 21.</p>