title: App crashes after trying to plot data from firebase using MpAndroid Chart
body: <p>I'm trying to plot temperature data that i get from a sensor in my app using MpAndroid chart. when i launch the activity that contains the graph my app crashes
  here's my code it's messy i'm a newbie. i'd appreciate any  help</p>
  <p><a href="https://i.stack.imgur.com/bo06F.png" rel="nofollow noreferrer">enter image description here</a></p>
  <p><a href="https://i.stack.imgur.com/Fsbax.png" rel="nofollow noreferrer">enter image description here</a></p>