title: Android Facebook hash key for signed APK sometimes change
body: <p>I'm using the Facebook login integration to my app. I configured hash key Facebook for signed APK and run successfully. But sometimes when i release a new APK file, the hash key is not valid any more ("invalid key hash facebook android does not match any stored").</p>
  
  <p>I read this link below, found that "Also, depending on the PC, sometimes the key can change and if so, the hash changes and you'll have to just accommodate for that"
  <a href="https://stackoverflow.com/questions/12291134/android-hash-key">android hash key</a></p>
  
  <p>Could you please hep me to explain more detail about this? 
  Is the hash key Facebook for signed APK sometimes changed? how about when the app is uploaded to play store?</p>
  
  <p>Thanks so much.</p>