title: Illegal State Exception when trying to generate an image from a GraphView
body: <p>I am trying to generate a image from a GrapView and I get the following error, despite I've set hardwareAccelerated to true:</p>
  
  <pre><code>java.lang.IllegalStateException: GraphView must be used in hardware accelerated mode.You can use android:hardwareAccelerated="true" on your activity. Read this for more info:https://developer.android.com/guide/topics/graphics/hardware-accel.html
  </code></pre>
  
  <p>Here is the code where I get the error:</p>
  
  <pre><code>graphView.addSeries(RepresentationHelper.getHashMapnewAPI().get(object.getName()));
              graphView.setTitle("");
  
              //setting y label for bounds with the min and max value obtained from the request
              graphView.getViewport().setYAxisBoundsManual(true);
              double low = graphView.getSeries().get(0).getLowestValueY();
              double high = graphView.getSeries().get(0).getHighestValueY();
              graphView.getViewport().setMinY(low);
              graphView.getViewport().setMaxY(high);
  
              graphView.getGridLabelRenderer().setHorizontalLabelsVisible(false);
              graphView.getGridLabelRenderer().setVerticalLabelsVisible(false);
              graphView.getGridLabelRenderer().setHighlightZeroLines(false);
              graphView.getGridLabelRenderer().setGridColor(Color.WHITE);
  
              Bitmap bitmap;
              graphView.setDrawingCacheEnabled(true);
              bitmap = Bitmap.createBitmap(graphView.getDrawingCache());
              graphView.setDrawingCacheEnabled(false);
  
              ImageView imageView = (ImageView) convertView.findViewById(R.id.imageView);
              //imageView.setImageDrawable(context.getResources().getDrawable(R.drawable.grafico_definitivo));
              imageView.setImageBitmap(bitmap);
  </code></pre>