JPanel的Java AWT边框不起作用

Question

For some reason my borders aren't showing for my panels and i am unsure why, is there something i'm missing?

I have a main class which runs the frame class as well as other classes separate to the GUI

This is the code from my frame class:

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

public class Frame
{
    public static int xsize;
    public static int ysize;

    public static void main()
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                JFrame frame = new MainFrame("Warlock of Firetop Mountain");

                //Implementing Toolkit to allow computer to get dimensions of screen and assign them to two int values
                Toolkit tk = Toolkit.getDefaultToolkit();
                Frame.xsize = (int) tk.getScreenSize().getWidth();
                Frame.ysize = (int) tk.getScreenSize().getHeight();

                frame.setTitle("Warlock of Firetop Mountain");
                frame.setSize(new Dimension(xsize, ysize));
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setResizable(true);
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
}

The frame.java takes its panels from MainFrame.java:

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

public class MainFrame extends JFrame
{
    private Panel1 storyPanel;
    private Panel2 statsPanel;
    private Panel3 commandsPanel;

    public MainFrame(String title)
    {
        super(title);

        // Setting Layout
        setLayout(new BorderLayout());

        storyPanel = new Panel1();
        statsPanel = new Panel2();
        commandsPanel = new Panel3();

        Container p = getContentPane();

        p.add(storyPanel, BorderLayout.WEST);
        p.add(statsPanel, BorderLayout.EAST);
        p.add(commandsPanel, BorderLayout.SOUTH);

    }
}

This calls up my three panels which look like this:

import javax.swing.JPanel;
import javax.swing.BorderFactory;
import java.awt.Dimension;
import java.awt.Color;

public class Panel1 extends JPanel
{
    public Panel1()
    {
        //Set size of Panel1
        int xsizeP1 = (Frame.xsize / 2);
        int ysizeP1 = (Frame.ysize / 3 * 2);
        setPreferredSize(new Dimension(xsizeP1, ysizeP1));

        setBorder(BorderFactory.createLineBorder(Color.black));
    }
}

when the code runs the window launches as full screen but no borders or possibly panels are visible.

Thanks for any help, sorry if my questions are tedious, i'm relatively new to programming.

This is roughly what i want my panels to look like, eventually ill add in components to the panel and use GridBagConstraints to control the formatting

Answer 1

// this creates the JPanels and sets their preferred sizes
JFrame frame = new MainFrame("Warlock of Firetop Mountain");

//this sets your size static contents -- after the above's been done!
Toolkit tk = Toolkit.getDefaultToolkit();
Frame.xsize = (int) tk.getScreenSize().getWidth();
Frame.ysize = (int) tk.getScreenSize().getHeight();

You're setting preferred sizes of all your JPanels to 0, 0, and so you're not seeing any borders. Your sizing is being created after you've created your JPanels, and this method of sizing looks dangerous to me.

---

OK, thanks for posting an image of the desired GUI. My recommendations are:

• First and foremost, don't try setting sizes as you're doing.
• Instead, let the components and their layout managers size themselves.
• Nest JPanels, each using its own layout manager to allow you to simply create complex GUI's.
• When displaying images / ImageIcons, let them set the sizes of things as well.
• If your GUI starts up with no icons displaying, consider creating a blank ImageIcon with a blank image of the right size as a placeholder icon.

---

For example, something like this:

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Insets;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import javax.swing.*;

@SuppressWarnings("serial")
public class TomGuiPanel extends JPanel {
    // rows and cols for jtextarea
    private static final int CURRENT_AREA_ROWS = 20;
    private static final int CURRENT_AREA_COLS = 40;

    // columns for command jtextfied
    private static final int COMMANDS_FIELD_COLS = 50;

    // size of GUI component gaps
    private static final int EB_GAP = 3;
    private static final int NUMBER_OF_OPTIONS = 5;

    // number if ImageIcons displayed within the user image char JList
    private static final int CHAR_IMG_VISIBLE_ROWS = 5;

    // a guess of the width of the largest image icon in the JList
    // You'd use a different number
    private static final int USER_IMG_CHAR_IMG_WIDTH = 70;

    private JTextArea currentTextArea = new JTextArea(CURRENT_AREA_ROWS, CURRENT_AREA_COLS);
    private JTextField commandsField = new JTextField(COMMANDS_FIELD_COLS);
    private EnterAction enterAction = new EnterAction("Enter");
    private DefaultListModel<Icon> charImgListModel = new DefaultListModel<>();
    private JList<Icon> charImgList = new JList<>(charImgListModel);

    public TomGuiPanel() {
        JPanel topBtnPanel = new JPanel(new GridLayout(1, 0, EB_GAP, EB_GAP));
        String[] btnTexts = { "Inventory", "Options", "Save", "Load" };
        for (String txt : btnTexts) {
            topBtnPanel.add(new JButton(txt));
        }

        JPanel characteristicsPanel = new JPanel(new GridBagLayout());
        addCharacteristics(characteristicsPanel, "HP", 20, 0);
        addCharacteristics(characteristicsPanel, "Attack", 12, 1);
        addCharacteristics(characteristicsPanel, "Defence", 8, 2);
        addCharacteristics(characteristicsPanel, "Agility", 9, 3);
        addCharacteristics(characteristicsPanel, "Luck", 2, 4);

        JScrollPane imgListPane = new JScrollPane(charImgList);
        imgListPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
        charImgList.setVisibleRowCount(CHAR_IMG_VISIBLE_ROWS);
        charImgList.setPrototypeCellValue(createProtoType());

        JPanel rightPanel = new JPanel(new BorderLayout(EB_GAP, EB_GAP));
        rightPanel.add(topBtnPanel, BorderLayout.PAGE_START);
        rightPanel.add(imgListPane, BorderLayout.CENTER);
        rightPanel.add(characteristicsPanel, BorderLayout.LINE_END);

        JPanel optionsPanel = new JPanel(new GridLayout(1, 0));
        for (int i = 0; i < NUMBER_OF_OPTIONS; i++) {
            String text = "Option " + (i + 1);
            optionsPanel.add(new JCheckBox(text));
        }

        currentTextArea.setWrapStyleWord(true);
        currentTextArea.setLineWrap(true);
        currentTextArea.setFocusable(false);
        JScrollPane taScrollPane = new JScrollPane(currentTextArea);
        taScrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

        JPanel centerPanel = new JPanel(new BorderLayout());
        centerPanel.add(taScrollPane, BorderLayout.CENTER);
        centerPanel.add(rightPanel, BorderLayout.LINE_END);
        centerPanel.add(optionsPanel, BorderLayout.PAGE_END);

        JPanel commandsPanel = new JPanel();
        commandsPanel.setLayout(new BoxLayout(commandsPanel, BoxLayout.LINE_AXIS));
        commandsPanel.add(commandsField);
        commandsPanel.add(Box.createHorizontalStrut(EB_GAP));
        commandsPanel.add(new JButton(enterAction));
        commandsPanel.add(Box.createHorizontalStrut(EB_GAP));
        commandsPanel.add(new JButton(new ExitAction("Exit", KeyEvent.VK_X)));
        commandsField.setAction(enterAction); // use same action for button and
                                              // text field

        setBorder(BorderFactory.createEmptyBorder(EB_GAP, EB_GAP, EB_GAP, EB_GAP));
        setLayout(new BorderLayout(EB_GAP, EB_GAP));
        add(centerPanel, BorderLayout.CENTER);
        add(commandsPanel, BorderLayout.PAGE_END);
    }

    private void addCharacteristics(JPanel cPanel, String text, int value, int row) {
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridx = 0;
        gbc.gridy = row;
        gbc.insets = new Insets(5, 5, 5, 5);
        gbc.weightx = 1.0;
        gbc.weighty = 0.0;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.anchor = GridBagConstraints.WEST;

        cPanel.add(new JLabel(text), gbc);

        gbc.insets.left = 20;
        gbc.anchor = GridBagConstraints.EAST;
        gbc.gridx = 1;
        cPanel.add(new JLabel(String.valueOf(value)), gbc);

    }

    private Icon createProtoType() {
        int w = USER_IMG_CHAR_IMG_WIDTH;
        int h = w;
        BufferedImage img = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
        Icon icon = new ImageIcon(img);
        return icon;
    }

    private class EnterAction extends AbstractAction {
        public EnterAction(String name) {
            super(name);
            int mnemonic = (int) name.charAt(0);
            putValue(MNEMONIC_KEY, mnemonic);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            String text = commandsField.getText();
            currentTextArea.append(text + "\n");
            commandsField.selectAll();
        }
    }

    private class ExitAction extends AbstractAction {
        public ExitAction(String name, int mnemonic) {
            super(name);
            putValue(MNEMONIC_KEY, mnemonic);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            Component source = (Component) e.getSource();
            Window win = SwingUtilities.getWindowAncestor(source);
            win.dispose();
        }
    }

    private static void createAndShowGUI() {
        TomGuiPanel mainPanel = new TomGuiPanel();

        JFrame frame = new JFrame("Tom's GUI");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

Would create this realizable GUI:

Note that the GUI is roughly made, has no functionality other than the enter and exit buttons.