i can open a PDF as img in a JFrame, no problem, but i will not open a new Window for it, the PDF must be shown in a jInternalFrame.
I create with Netbeans a Design and will open the Document with following code:
(Apache PDFBox)

public void openFile(){
        
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    File file = new File("/home/ritzmo/Labor_Clotten/PDF_Befunde/test.pdf");
                    PDDocument pdffile = Loader.loadPDF(file);
                    PDFRenderer pdfRenderer = new PDFRenderer(pdffile);
                    BufferedImage image = pdfRenderer.renderImage(0);
                    JLabel label = new JLabel(new ImageIcon(image));
                    jInternalFrame2.setTitle("PDF G");                                     
                    jInternalFrame2.add(new JScrollPane(label));
                    jInternalFrame2.setVisible(true);
                } catch (IOException e) {
                }
            }
        });
    }

The jInternalFrame lies on the Main JFrame, but the PDF will not be shown.
I search on google, chatgpt over 3 hours but found no answers.

Anybody have an idea?

Greats Moritz

The Program start with no errors.
I search on chatgpt and google over 3 hours but found no answers.

Anybody have an idea?