为JPanel设置灵活的大小

Question

My ContentPane contains several JPanels that in turn contain JTabbedPanes and other things. How can I make those JPanels to change their size as user shrinks or expands the window. Is there any way to set up a percentage size?

JPanel panelOne = new JPanel;
panelOne.setSize( // % of );

Answer 1

You can use a variety of layout methods on ContentPanes. For something that scales based on size in relation to the canvas, you can try using a SpringLayout and define the borders in relation to a content pane itself. Other elements can be constrained to that anchored element or to the content pane.

You can use constraints to stretch panels based on the ContentPane or other elements.

You can visually plan SpringLayout (and other possible layouts, such as Mig, Grid, etc.) using WindowBuilder for Eclipse. Depending on the size and scale of your Layout, you may find other layouts to be more practical based on your requirements or preference.

Answer 2

Make use of appropriate layout managers, that's what they are there for. They take care of all the dirty work involved in monitoring changes to the parent container and calculating the required settings based on the changes.

Take a look at Laying Out Components Within a Container

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.CompoundBorder;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;

public class TestSizableComponents {

    public static void main(String[] args) {
        new TestSizableComponents();
    }

    public TestSizableComponents() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JTabbedPane tabbedPane = new JTabbedPane();
                for (int index = 0; index < 10; index++) {
                    tabbedPane.add(Integer.toString(index), new TabPane(Integer.toString(index)));
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new HeaderPane(), BorderLayout.NORTH);
                frame.add(tabbedPane);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class HeaderPane extends JPanel {

        public HeaderPane() {

            setLayout(new GridBagLayout());
            add(new JLabel("Look ma, no hands"));
            setBorder(new CompoundBorder(new LineBorder(Color.RED), new EmptyBorder(10, 10, 10, 10)));

        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 100);
        }

    }

    public class TabPane extends JPanel {

        public TabPane(String name) {

            setLayout(new GridBagLayout());
            add(new JLabel(name));
            setBorder(new EmptyBorder(10, 10, 10, 10));

        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

    }

}