public void appendLog(String text)
{
File logFile = new File("sdcard/log.file");
if (!logFile.exists())
{
  try
  {
     logFile.createNewFile();
  }
  catch (IOException e)
  {
     // TODO Auto-generated catch block
     e.printStackTrace();
  }
}
try
{
  //BufferedWriter for performance, true to set append to file flag
  BufferedWriter buf = new BufferedWriter(new FileWriter(logFile, true));
  buf.append(text);
  buf.newLine();
  buf.close();
}
catch (IOException e)
{
  // TODO Auto-generated catch block
  e.printStackTrace();
}
}