JScrollPane不会截断JLabel文本

Question

So I'm trying to create a table with information, and the rows in the table exceeds the height of the JFrame, therefor I'm trying to use a JScrollPane as a solution.

When I add the JPanel to the Frame it truncates the JLabels text, if it exceeds the bounds of the frame, as seen in the picture below:

The code:

    public class TestApplication extends JPanel{
JPanel headers = new JPanel(new GridLayout(1, 5));

JPanel informationTable = new JPanel();
JPanel[] rows = new JPanel[30];

public TestApplication(){

    headers.add(new JLabel("Name"));
    headers.add(new JLabel("City"));
    headers.add(new JLabel("Adress"));
    headers.add(new JLabel("Phone"));
    headers.add(new JLabel("Mail"));

    informationTable.setLayout(new BoxLayout(informationTable, BoxLayout.Y_AXIS));

    //Populating the table with 20 rows
    for(int i = 0; i < 30; i++){
        rows[i] = new JPanel();

        rows[i].setLayout(new GridLayout(1, 6));

        rows[i].add(new JLabel("Undefined name"));
        rows[i].add(new JLabel("Undefined city"));
        rows[i].add(new JLabel("1529th Avenue street name"));
        rows[i].add(new JLabel("Undefined Phone"));
        rows[i].add(new JLabel("Undefined Mail"));

        informationTable.add(rows[i]);
    }
    super.setLayout(new BorderLayout());
    super.add(headers, BorderLayout.NORTH);
    super.add(informationTable, BorderLayout.CENTER);
}

However when I place the JPanel with the rows inside the JScrollPane it doesn't truncate the JLabel text, which then exceeds the JFrame, and miss aligns all of the columns, as seen in the picture below: The code:

    public class TestApplication extends JPanel{
JPanel headers = new JPanel(new GridLayout(1, 5));

JPanel informationTable = new JPanel();
JPanel[] rows = new JPanel[30];
JScrollPane scrollTable = new JScrollPane(informationTable);

public TestApplication(){

    headers.add(new JLabel("Name"));
    headers.add(new JLabel("City"));
    headers.add(new JLabel("Adress"));
    headers.add(new JLabel("Phone"));
    headers.add(new JLabel("Mail"));

    informationTable.setLayout(new BoxLayout(informationTable, BoxLayout.Y_AXIS));

    //Populating the table with 20 rows
    for(int i = 0; i < 30; i++){
        rows[i] = new JPanel();

        rows[i].setLayout(new GridLayout(1, 6));

        rows[i].add(new JLabel("Undefined name"));
        rows[i].add(new JLabel("Undefined city"));
        rows[i].add(new JLabel("1529th Avenue street name"));
        rows[i].add(new JLabel("Undefined Phone"));
        rows[i].add(new JLabel("Undefined Mail"));

        informationTable.add(rows[i]);
    }
    scrollTable.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);

    super.setLayout(new BorderLayout());
    super.add(headers, BorderLayout.NORTH);
    super.add(scrollTable, BorderLayout.CENTER);
}

The main method for both examples is the same. I don't think it has anything to do with the problem, but it can be seen in the code below:

    public static void main(String[] args) {
    JFrame main = new JFrame("JScrollPane exceeds bounds");

    TestApplication app = new TestApplication();

    main.add(app);

    main.setSize(600, 513);
    main.setLocationRelativeTo(null);
    main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    main.setVisible(true);
}

Answer 1

When I add the JPanel to the Frame it truncates the JLabels text, if it exceeds the bounds of the frame

Correct, because the layout manager forces the components to be sized in the space available.

However when I place the JPanel with the rows inside the JScrollPane it doesn't truncate the JLabel text, which then exceeds the JFrame

Correct, because the point of using a JScrollPane is to allow each component to be displayed at its preferred size. If the component size doesn't fit then scrolling will result.

If you want to control the width of the panel to fit the width of the scrollpane then you need to implement the Scrollable interface on your panel and override the getScrollableTracksViewportWidth() method to return Boolean.TRUE . Read the API for more information about the Scrollable interface.

An easy way to do this is to use the Scrollable Panel which has methods to allow you to control the scrollable properties.

Answer 2

The only solution that is apparent to me is to overwrite the GridLayout you use. Does not sound nice, but is actually done quite easily:

package scrollPaneAndBoxLayout;

import java.awt.Container;
import java.awt.Dimension;
import java.awt.GridLayout;

public class MyGridLayout extends GridLayout {

    public MyGridLayout(int rows, int cols) {
        super(rows, cols);
    }

    public Dimension preferredLayoutSize(Container parent) {
        return new Dimension(parent.getWidth(), (int) super.preferredLayoutSize(parent).getHeight());
    }

}

To explain it, preferredLayoutSize() returns the size the whole component applying the Layout will have if possible (which it will be most of the cases). I set the width of this to the width of the parent component, so the container in which you put your table, while the height is taken from the original GridLayout class.

Another solution would be to use a JTable instead of your JPanel-construction but when you already implemented it this way I doubt that it would be easier for you to revise the whole concept.