title: Draw on achartengine on touch
body: <p>i'm trying to compare two values from two series at the same X value from the chart below:</p>
  
  <p><img src="https://i.stack.imgur.com/Hj0TT.png" alt="enter image description here"></p>
  
  <p>i can get the values with .getCurrentSeriesAndPoint() but it is not really usable
  is it possible with the current achartengine api to detect touch on blue area and draw black rectangle around those two values?</p>