private void addIconView(final int iconId) {
        final ImageView iv = ViewUtils.createIconView(getContext(), iconId);
        iv.setMaxWidth(ViewUtils.spToPixel(12));
        iv.setMaxHeight(ViewUtils.spToPixel(12));
        matrixGrid.addView(iv, createLayoutParams());
    }
(re-)initializes the matrix with given data. Matrix data is deleted in the process
main/src/main/java/cgeo/geocaching/ui/CheckboxMatrixView.java