title: measure area of irregular polygon in android
body: <p>I am developing one application in which i have draw the polygon on map and map that I have used is not google,Its Mapsforge opensource offline map library.i have easily draw polygon on map by converting geopoint into pixcel point.but here i want to find are of that irregular polygon,and for that i have make lots of try but its getting me unsuccess..
  I have tried with calculate area with basic Math but its not working in this case be case pixcel are change accodingly while change zoom level.
  Here is Math logic :
  <a href="http://www.wikihow.com/Calculate-the-Area-of-a-Polygon">Math calculation</a></p>
  
  <pre><code> for(int miAreainc = 0;miAreainc  &lt; x.length-1; miAreainc++)
                   {
                       sumX += x[miAreainc] * y[miAreainc + 1];
                       sumY += y[miAreainc] * x[miAreainc + 1];
                   }
                   int unit = ((sumX - (sumY)) / 2);
                   AppLog.showLogE(TAG,"UNIT &gt;&gt; " + unit);
  </code></pre>
  
  <p>I found that funcation stay at server side which get area from geopoint array,but here I want to make it offline.
  I have tried so far but not getting any clue or result ..
  Please help me out this..
  Thanks</p>