Image desapears in JPanel when read from database

Question

good evening,

I have this part of code:

My problem is when I try to display the image of the BLOB Type. I am working with Netbeans IDE and apach derby database.

like this all things are well, but if I remove the line : JOptionPane.showMessageDialog(null, "hello"); the image apears and desapears fast,

String req = "select * from viewpiece where idpiece = "+idpiece;
        myConnection = MyConnection.getMyConnection() ;
        ResultSet rs = myConnection.executeSQL(req);  

        try {   
            if (rs.next()) {

                TextFieldValeur.setText(rs.getString(2));
                TextFieldMonnaie.setText(rs.getString(5));
                TextFieldPays.setText(rs.getString(20));

                Blob Rectoblob = rs.getBlob(21);
                byte[] RectoByte = Rectoblob.getBytes(1, (int)(Rectoblob.length()));
                 try {
                    rectoBufferedImage = ImageIO.read(new ByteArrayInputStream(RectoByte));
                    g = panelImageRecto.getGraphics();

                   JOptionPane.showMessageDialog(null,  "hello");
                   g.drawImage(rectoBufferedImage, 10, 20,175,175, null);

                } catch (IOException ex) {
                    Logger.getLogger(PieceDetaillee.class.getName()).log(Level.SEVERE, null, ex);
                }

            }

        } catch (SQLException ex) {
            JOptionPane.showMessageDialog(rootPane, "Erreur recherche de details\n"+req);
        } 

where is the problem? and why that line of displaying message Hello is a solution?.

any help please? thank you very much.

Answer 1

Your problem is that you're using getGraphics() to get the Graphics context, and then drawing with it. This Graphics object is short-lived, and is not a safe way to draw an image in a Swing GUI. Much better would be to draw the image in a JPanel's paintComponent method using the Graphics object provided there for you by the JVM. Either that or display it as an ImageIcon in a JLabel.