Adding JScrollPane to JPanel

1
votes

I'm trying to add a JScrollPane to an JPanel from a separate class. And thanks to some questions, which were asked so far, I could help myself create them. But my problem is still a little bit special. I want to display an image on a JPanel and if the image is to large for the panel, I want to add scrollbars. But the scrollbars won't appear. (When I set the ScrollPaneConstants to ****_SCROLLBAR_ALWAYS the frame of the bar appears, but without the bars to scroll).

I guess i have to connect the imagesize with the bars, so that they appear?

Some pieces of my code:

MainWindow

public class Deconvolutioner extends JFrame
{
Draw z;
Picturearea picturearea;

class Draw extends JPanel
{
    public void paint(Graphics g)
    {

    }
}

public Deconvolutioner()
{
    setTitle("Deconvolutioner");
    setLocation(30,1);
    setSize(1300,730);
    super.setFont(new Font("Arial",Font.BOLD,11));
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setResizable(false);

    FlowLayout flow = new FlowLayout(FlowLayout.CENTER);

    this.setLayout(flow);

    picturearea = new Picturearea();
    picturearea.setLayout(new GridBagLayout());

    JScrollPane scrollPane = new JScrollPane(picturearea, 
    ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, 
    ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);

    scrollPane.setPreferredSize(new Dimension(1000, 664));

    getContentPane().add(scrollPane, flow); // add scrollpane to frame


    add(z = new Draw());
    setVisible(true);

}
}

JPanel Class

public class Picturearea extends JPanel
{
BufferedImage image;
int panelWidth, panelHeight, imageWidth, imageHeight;

public Picturearea()
{
    setBackground(new Color(210,210,210));
    setBorder(LineBorder.createBlackLineBorder());


    setVisible(true);
}

@Override
public void paintComponent(Graphics g) 
{
    super.paintComponent(g);
    g.drawImage(image, 0, 0, this);

}

public void setPicture(BufferedImage picture)
{
    try 
    {                
        image = picture;
    } 
    catch (Exception e) 
    {
        System.err.println("Some IOException accured (did you set the right path?): ");
        System.err.println(e.getMessage());
    }
    repaint();
}

}

Thanks for your time.

2
javaswingawtjscrollpane

2 Answers

2
votes

The problem is that the JScrollPane has no way to know if it should display scroll bars or not, since the Picturearea it contains doesn't tell anything about its preferred size (or rather, it returns the preferred size based on its layout and on the components it contains. But since it doesn't contain any component, the returned preferred size is probably (0, 0)).

I would simply use a JLabel instead of the custom Picturearea class. A JLabel can display an image just fine, and it returns the appropriate Dimension when asked for its preferred size.

0
votes

You can create a JLabel first and then add the Label to JPanel picturearea before creating instance for JScrollPane .

Have a try and it will work.

Example code is as follows:

    JLabel imageLabel = new JLabel(new ImageIcon("d:\\099.jpg"));
    picturearea.add(imageLabel);**

    JScrollPane scrollPane = new JScrollPane(picturearea,
            ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,
            ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);