调整JPanel的高度

Question

I have a top panel with a flow layout that has a textfield and label. I need to add more text fields and labels below the first line. I realized theres no real way of forcing a new line in flowlayout so I was just going to make a new panel and put it underneath the top one. The problem is theres a gap now because the top panels height is too tall. Is there a way to resize the panel so its width adjusts to screens automatically but I want to adjust the height of the new panel, so the gap is smaller. The two textfields up top are in the top panel with a flowlayout, The 3 textfields below are in a new panel with a flowlayout, is there a way to make the 3 textfields go right under the 2 textfields up top? Also, the whole frame is in a gridlayout.

frame.setLayout(new GridLayout(0,1));
Static JPanel topPanel = new JPanel(new flowlayout);
Static JPanel searchPanel = new JPanel(new flowlayout);
Static JPanel statusPanel = new JPanel(new gridLayout(2,1));
Static JPanel categoryPanel = new JPanel(new GridLayout(0.2));
Static JPanel btnPanel = new JPanel(new GridLayout(0,3));
frame.pack();
topPanel.add(searchPanel);
JPanel container2 = new JPanel(new BorderLayout()):
container2.add(topPanel, BorderLayout.North);
frame.getContentPane().add(container2);
frame.getContentPane().add(statusPanel);
frame.getContentPane().add(catergoryPanel);
frame.getContentPane().add(btnPanel);

Answer 1

The JPanel with the GridLayout is the problem - It's probably added to BorderLayout.CENTER of the container and therefore it stretches across the whole available space. It also has equal cell sizes. Either wrap the grid into a BorderLayout and add it to BorderLayout.NORTH or use a GridBagLayout for the panels.

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Here's an example that demonstrates how the panels are laid out in your example and how the are laid out in other layouts. I think this will make it clear why your GridLayout behaved in that way.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Insets;

import javax.swing.BorderFactory;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Example {

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Example();
            }
        });
    }

    public Example() {

        // GridLayout

        JPanel container1 = new JPanel(new GridLayout(2, 1));
        container1.add(createExamplePanel());
        container1.add(createExamplePanel());

        // GridLayout inside BorderLayut (NORTH)

        JPanel panel = new JPanel(new GridLayout(2, 1, 0, 5 /* margin */)); // You could also use other layouts here, e.g. a BoxLayout
        panel.add(createExamplePanel());
        panel.add(createExamplePanel());
        JPanel container2 = new JPanel(new BorderLayout());
        container2.add(panel, BorderLayout.NORTH);

        // GridBagLayout

        JPanel container3 = new JPanel(new GridBagLayout());
        GridBagConstraints constraints = new GridBagConstraints();
        constraints.anchor = GridBagConstraints.PAGE_START;
        constraints.fill = GridBagConstraints.HORIZONTAL;
        constraints.insets = new Insets(0, 0, 5 /* margin */, 0);
        constraints.weightx = 1.0;
        container3.add(createExamplePanel(), constraints);
        constraints.gridy = 1;
        constraints.weighty = 1.0;
        constraints.insets = new Insets(0, 0, 0, 0);
        container3.add(createExamplePanel(), constraints);

        JPanel contentPane = new JPanel(new GridLayout(1, 3, 5, 5));
        contentPane.add(createTitledPanel(container1, "GridLayout"));
        contentPane.add(createTitledPanel(container2, "GridLayout inside BorderLayout (NORTH)"));
        contentPane.add(createTitledPanel(container3, "GridBagLayout"));

        JFrame frame = new JFrame("Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setContentPane(contentPane);
        frame.setSize(800, 600);
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JPanel createTitledPanel(JComponent content, String title) {
        JPanel panel = new JPanel(new BorderLayout());
        panel.add(content);
        panel.setBorder(BorderFactory.createTitledBorder(title));
        return panel;
    }

    private JPanel createExamplePanel() {
        JPanel panel = new JPanel();
        panel.add(new JLabel("Panel"));
        panel.setBorder(BorderFactory.createLineBorder(Color.GRAY));
        return panel;
    }

}