Java: JScrollPane disappears when it is full

Question

I want to view some information about some objects of my program. For that I am creating a JPanel for every Object with it's information. These panels get packed together in a Panel which I add to a ScrollPane.

Works perfect if there are just a few Objects so all Information can get displayed without scrolling. As soon as there are more, the whole Panel just disappears in a way like it is minimized.

I am sorry that I couldn't extract a small codesnippet to reproduce the mistake. I made it as small as possible. So I have to give you three Classes:

Program: Creates a TreeMap of Objects and works on it. Here it is just initializing a List of Integers.

   import java.util.TreeMap;




   public class Program {


// Set ObjectNumber here!
static int numberObjects = 32;


static TreeMap<Integer, Integer> objects = new TreeMap<Integer, Integer>();

static TestFrame frame;

public static void main(String[] args) {

    init();

}

public static void init() {

    for (int i=0; i < numberObjects; i++) {
        objects.put(i, i);
    }

    frame = new TestFrame(objects);

    frame.repaint();

}


}

TestFrame: It extends JFrame, sets it self to maximimzed and Border Layout. After that, it adds a JPanel from my class TestPanel to the east.

 import java.awt.BorderLayout;

 import java.awt.Dimension;

 import java.awt.Frame;

 import java.util.TreeMap;

 import java.awt.GridLayout;

 import java.awt.Toolkit;

 import java.util.TreeMap;


 import javax.swing.JFrame;


 public class TestFrame extends JFrame {


TreeMap<Integer, Integer> objects;

TestPanel testPanel;

public TestFrame(TreeMap<Integer, Integer> objects) {

    this.objects = objects;
    setTitle("Program");
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    this.setExtendedState(Frame.MAXIMIZED_BOTH);

    init();

}

public void init() {

    setLocationRelativeTo(null);
    setLayout(new BorderLayout());

    testPanel = new TestPanel(objects);
    this.add(testPanel, BorderLayout.EAST);

    setVisible(true);

}


 }

TestPanel: It extends JPanel. Goes through all objects and add a label with the integer-value to an array names[]. Then goes for every obect again to build an panel just for this object, add a panel with text "Name:" and the label from the names[]-array. With GridBagLayout. Now it packs all panels of the objects in one panel "innerPanel". This is added to the scrollpane. The scrollpane gets added to the class (TestPanel).

import java.util.TreeMap;


import javax.swing.JPanel;

import javax.swing.JScrollPane;

import javax.swing.SwingConstants;


import java.awt.Font;

import java.awt.Graphics;

import java.awt.GridBagConstraints;

import java.awt.GridBagLayout;

import java.awt.GridLayout;

import java.awt.Label;


import javax.swing.BorderFactory;


public class TestPanel extends JPanel {

GridBagConstraints gridBagConstraints = new GridBagConstraints();

TreeMap<Integer, Integer> objects;

Label[] names;

JPanel[] objectPanel;

JPanel innerPanel;

Font fontLabelName = new Font("Arial", Font.BOLD, 20);



public TestPanel (TreeMap<Integer, Integer> objects) {

    this.objects = objects;

    names = new Label[objects.size()];

    objectPanel = new JPanel[objects.size()];

    this.setLayout(new GridBagLayout());

    for(int i=0; i<objects.size(); i++) {
        Label tempLabel = new Label(Integer.toString(objects.get(i)), SwingConstants.LEFT);
        tempLabel.setFont(fontLabelName);
        names[i]=tempLabel;
    }

    for (int i=0; i<objects.size(); i++) {

        JPanel tempPanel = new JPanel();
        tempPanel.setLayout(new GridBagLayout());
        objectPanel[i] = tempPanel;

        gridBagConstraints.gridx = 0;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.gridwidth = 2;
        gridBagConstraints.gridheight = 1;
        Label nameLabel = new Label("Name: ", SwingConstants.LEFT);
        nameLabel.setFont(fontLabelName);
        objectPanel[i].add(nameLabel, gridBagConstraints);

        gridBagConstraints.gridx = 2;
        gridBagConstraints.gridy = 0;
        gridBagConstraints.gridwidth = 2;
        gridBagConstraints.gridheight = 1;
        objectPanel[i].add(names[i], gridBagConstraints);
    }

    innerPanel = new JPanel();
    innerPanel.setLayout(new GridLayout(0,1));

    for (int i = 0; i<objects.size(); i++) {
        innerPanel.add(objectPanel[i]);
    }

    JScrollPane scrollPane = new JScrollPane(innerPanel);
    // scrollPane.setBorder( BorderFactory.createEmptyBorder() );
    scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
    scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

    this.add(scrollPane);

}

}

Works perfectly as seen in the screenshot with my screenresolution for 31 objects, but the scrollpane nearly disappears if i use 32 objects.

31 objects

32 objects

Would be really thankfull if anybody could help me solve it or link a matching post - I couldn't find one with google/search.

artpap artpap · Accepted Answer · 2016-02-01T13:13:46

Try setting a different layout in your TestPanel. BorderLayout is a good choice if you are going to add only one object in your panel (the scollpane in your case), and you want the object to occupy all the space of the panel.

this.setLayout(new BorderLayout());

Java: JScrollPane disappears when it is full

1 Answers