Dynamic JScrollPane in JPanel

[Frederic Poesson]

Hello

I'm looking for a reset size of the scrolling of a Jpanel after resizing.
I do my calculation with the size of labels displayed
The size is just for multiples of two, but not for others.

I don't see how to solve my problem
Here is my code

package test;

import javax.swing.*;
import java.awt.*;

class MyPanelScrolled extends JPanel {

    private JLabel[] labels = new JLabel[100];
    final int TOTAL_CELLULE = 100;

    int hauteurAffichable = 0;

    public MyPanelScrolled(){

        setBackground(Color.WHITE);
        setBorder(BorderFactory.createLineBorder(Color.GRAY));
        setLayout(new FlowLayout(FlowLayout.LEADING, 0, 0));
        setPreferredSize(new Dimension(0, 0));

        for(int i=0; i< TOTAL_CELLULE; i++){
            labels[i] = new JLabel("Label " + i);
            labels[i].setPreferredSize(new Dimension(150, 150));

            labels[i].setVerticalAlignment(JLabel.CENTER);
            labels[i].setHorizontalAlignment(JLabel.CENTER);
            labels[i].setBorder(BorderFactory.createMatteBorder(0, 0, 1,1, Color.GRAY));

            add(labels[i]);
        }
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        //Taille du panel
        Rectangle TaillePanel = getBounds();
        Rectangle TailleVisible = getVisibleRect();

        int height = (int)TaillePanel.getHeight();
        int width = (int)TaillePanel.getWidth();

        int colonne =  width / 150;
        int row = height / 150;

        int totalScroll = (150 * (TOTAL_CELLULE)) / colonne;


        setPreferredSize(new Dimension((colonne * (150)), totalScroll ));
        revalidate();
    }
}


public class TestScrollPane2 extends JFrame {

    private MyPanelScrolled panel;
    public TestScrollPane2(){

        setTitle("Scroll test panel");
        setSize(330, 200);

        Container contenu = getContentPane();

        panel = new MyPanelScrolled();

        JScrollPane scroll = new JScrollPane(panel);
        scroll.getVerticalScrollBar().setUnitIncrement(150);

        contenu.add(scroll, BorderLayout.CENTER);

        //pack();
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
    }

    public static void main(String[] args){

        new TestScrollPane2().setVisible(true);
    }
}

Thank you very much

[Rob Camick]

The paintComponent() method is used for custom painting, not for setting the preferred size of the component. You should definitely not be invoking revalidate() and setPreferredSize() from within that method. In fact there is no reason for you to override the paintComponent() method at all.

You should NOT be using setPreferredSize() anywhere in your code. Setting the preferred size is the job of the layout manager.

If you use an appropriate layout manager the preferred size will be determined for you and scrolling will work properly. Read the Swing tutorial on Layout Managers for more information and examples.

[Campbell Ritchie]

And welcome to the Ranch

[Frederic Poesson]

Rob Camick wrote:The paintComponent() method is used for custom painting, not for setting the preferred size of the component. You should definitely not be invoking revalidate() and setPreferredSize() from within that method. In fact there is no reason for you to override the paintComponent() method at all.

You should NOT be using setPreferredSize() anywhere in your code. Setting the preferred size is the job of the layout manager.

If you use an appropriate layout manager the preferred size will be determined for you and scrolling will work properly. Read the Swing tutorial on Layout Managers for more information and examples.

Actually my design method is to be the best (I'm newbie in java).
Thank you for the link. I used a JGridLayout GridLayout

Campbell Ritchie wrote:And welcome to the Ranch

Thank you

[Darryl Burke]

Frederic Poesson wrote:I used a JGridLayout

I think you mean GridLayout.