title: Android: Application becomes unresponsive after short delay
body: <p>I've noticed my whiteboard app becomes 'dormant' after a few seconds of no interaction, so that when something is newly drawn, there is horrible lag. This is without switching away from the app at all - I run it, it's there, I can draw and undo. But if I don't use it for 10 seconds and then try and draw a circle, there can be a second or so of wait before it updates and I get a straight line from start point to current position. So the code to start drawing is instant when the view is touched, but the updates aren't happening for a good while yet.</p>
  
  <p>The code is effectively the Fingerpaint demo drawing onto a custom bitmap, and I copy this bitmap to the view. I undo by copying the bitmap just before drawing starts. I have disabled the undo code to see if that was the issue, but the delay is still there, only far less pronounced. I notice the same lag sometimes happens in the Fingerpaint API demo.</p>
  
  <p>Anyone know why this is? Is there some odd setting I don't know about which causes an active app to go to sleep?</p>