title: How to detect Bluetooth state change using a broadcast receiver?
body: <p>I am trying to make an app that shows a toast when the device's Bluetooth turned on. I wanna do that even when my app is not running. So I should use a broadcast receiver, add some permissions, an intent-filter to android manifest and make a java class but I don't know the details.</p>
  
  <p>What should I do? Which permissions should I use?</p>