最近项目里要加入一个功能，是要将页面报表导出到pdf中，但是报表中有checkbox复选框，需要要后台利用itext生成，我生成复选框的方法如下：
PdfContentByte cb = writer.getDirectContent();
cb.moveTo(0, 0);
PdfFormField field = PdfFormField.createCheckBox(writer);
PdfAppearance tpOff = cb.createAppearance(20, 20);
PdfAppearance tpOn = cb.createAppearance(20, 20);
tpOff.rectangle(1, 1, 18, 18);
tpOff.stroke();
//
tpOn.setRGBColorFill(255, 128, 128);
tpOn.rectangle(1, 1, 18, 18);
tpOn.fillStroke();
tpOn.moveTo(1, 1);
tpOn.lineTo(19, 19);
tpOn.moveTo(1, 19);
tpOn.lineTo(19, 1);
tpOn.stroke();
field.setWidget(new Rectangle(100, 700, 120, 720), PdfAnnotation.HIGHLIGHT_INVERT);
field.setFieldName("Urgent");
field.setValueAsName("On");
field.setAppearanceState("Off");
// field.setAppearance(PdfAnnotation.APPEARANCE_NORMAL, "Off", tpOff);
// field.setAppearance(PdfAnnotation.APPEARANCE_NORMAL, "On", tpOn);
writer.addAnnotation(field);
但是不能生成像页面选中打钩的复选框，请问有什么好办法？在此感谢
