从找到的 AcroForm 表单域中获取页面

Question

我有一个现有的 PDF，我想打开它并将内容添加到特定 PDField（或具体 PDTerminalField，我认为这无关紧要）所在的页面。它可能在第一页或后面的任何一页。
我知道字段的名称，有了它，我可以查找它，甚至可以获得它在该页面上的尺寸和位置 (DRectangle mediabox = new PDRectangle((COSArray) fieldDict.getDictionaryObject(COSName.RECT));)

但是我找不到获取它所在页面的 number/index 的方法，因此我可以在正确的页面上书写。

PDAcroForm acroForm = pdfDocument.getDocumentCatalog().getAcroForm();
PDField docField = acroForm.getField("the_coolest_field");

int page = docField.???  // This is the missing part.


PDPageContentStream contentStream = new PDPageContentStream(pdfDocument, 
pdfDocument.getPage(page), PDPageContentStream.AppendMode.APPEND, true);
// now write something on the page where the field is in.

Answer 1

使用中给出的提示，我可以创建一个包含字段名称及其出现的（最后）页面的地图。

HashMap<String, Integer> formFieldPages = new HashMap<>();
for (int page_i = 0; page_i < pdf_document.getNumberOfPages(); page_i++) {
    List<PDAnnotation> annotations = pdf_document.getPage(page_i).getAnnotations(); //
    for (PDAnnotation annotation: annotations) {
        if (!(annotation instanceof PDAnnotationWidget)) {
            System.err.println("Unknown annotation type " + annotation.getClass().getName() + ": " + annotation.toString());
            continue;
        }
        String name = ((PDAnnotationWidget)annotation).getCOSObject().getString(COSName.T);
        if (name == null) {
            System.err.println("Unknown widget name: " + annotation.toString());
            continue;
        }
        // make sure the field does not exists in the map
        if (formFieldPages.containsKey(name)) {
            System.err.println("Duplicated widget name, overwriting previous page value " + formFieldPages.get(name) + " with newly found page " + page_i + ": " + annotation.toString());
        }
        formFieldPages.put(name, page_i);
    }
}

现在查找页面就这么简单

int page = formFieldPages.get(docField.getPartialName());

请注意，如果该小部件由于某种原因不存在，这可能会抛出 NullPointerException。

下面是之前的回答。我似乎错误那个方法，但我保留它以供参考：

I have found the /P element which seems like it could be the page:

int page = (int)currentField.getCOSObject().getCOSObject(COSName.P).getObjectNumber();
page = page - 5; // I couldn't figure out why it's off by 4, but tests showed that the actual PDF page 1 (index [0]) is represented by `\P {4, 0}`, page 2 ([1]) is called "5", page 3 ([2]) is "6", etc.

从找到的 AcroForm 表单域中获取页面

Get page from found AcroForm form field

java

pdfbox

acrofields