FlowLayout on top of GridLayout not working

问题

I\'m trying to create a hangman game and so far it\'s coming along GREAT, but the layout design just doesn\'t seem to fall into place! The alphabet is supposed to end up in a FlowLayout order on top of the Hangman picture with the buttons \"Restart\", \"Help\" \"Add New Word\" and \"Exit\" at the bottom! What am I doing wrong?

$\"hangman\"$

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

public class Hangman extends JFrame
{
    int i = 0;
    static JPanel panel;
    static JPanel panel2;
    static JPanel panel3;

    public Hangman()
    {
        JButton[] buttons = new JButton[26];

        panel = new JPanel(new FlowLayout());
        panel2 = new JPanel();
        panel3 = new JPanel();

        JButton btnRestart = new JButton(\"Restart\");
        btnRestart.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e)
            {

            }
        });

        JButton btnNewWord = new JButton(\"Add New Word\");
        btnNewWord.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e)
            {
                try
                {
                    FileWriter fw = new FileWriter(\"Words.txt\", true);
                    PrintWriter pw = new PrintWriter(fw, true);

                    String word = JOptionPane.showInputDialog(\"Please enter a word: \");

                    pw.println(word);
                    pw.close();
                }
                catch(IOException ie)
                {
                    System.out.println(\"Error Thrown\" + ie.getMessage());
                }
            }
        });

        JButton btnHelp = new JButton(\"Help\");
        btnHelp.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e)
            {
                String message = \"The word to guess is represented by a row \"
                   + \"of dashes, giving the number of letters and category of \"
                   + \"the word. \\nIf the guessing player suggests a letter \"
                   + \"which occurs in the word, the other player writes it \"
                   + \"in all its correct positions. \\nIf the suggested \"
                   + \"letter does not occur in the word, the other player \"
                   + \"draws one element of the hangman diagram as a tally mark.\"
                   + \"\\n\"
                   + \"\\nThe game is over when:\"
                   + \"\\nThe guessing player completes the word, or guesses \"
                   + \"the whole word correctly\"
                   + \"\\nThe other player completes the diagram\";
               JOptionPane.showMessageDialog(null,message, \"Help\",JOptionPane.INFORMATION_MESSAGE);
            }
        });

        JButton btnExit = new JButton(\"Exit\");
        btnExit.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e)
            {
                System.exit(0);
            }
        });

        ImageIcon icon = new ImageIcon(\"D:\\\\Varsity College\\\\Prog212Assign1_10-013803\\\\images\\\\Hangman1.jpg\");
        JLabel label = new JLabel();
        label.setIcon(icon);
        String  b[]=  {\"A\",\"B\",\"C\",\"D\",\"E\",\"F\",\"G\",\"H\",\"I\",\"J\",\"K\",\"L\",\"M\",\"N\",\"O\",\"P\",\"Q\",\"R\",\"S\",\"T\",\"U\",\"V\",\"W\",\"X\",\"Y\",\"Z\"};
        for(i = 0; i < buttons.length; i++)
        {
            buttons[i] = new JButton(b[i]);

            panel.add(buttons[i]);
        }
        panel2.add(label);

        panel3.add(btnRestart);
        panel3.add(btnNewWord);
        panel3.add(btnHelp);
        panel3.add(btnExit);
    }

    public static void main(String[] args) 
    {
        Hangman frame = new Hangman();
        frame.add(panel, BorderLayout.NORTH);
        frame.add(panel2, BorderLayout.CENTER);
        frame.add(panel3, BorderLayout.SOUTH);
        frame.pack();
        frame.setVisible(true);
    }
}

回答1:

Here are a few suggestions:

Use a GridLayout for the top panel; in this case, zero means the number of rows is determined by the specified number of columns and the total number of components in the layout:
```
JPanel north = new JPanel(new GridLayout(0, 9));
```

Here's an outline of how you can make your center panel have a reasonable initial size; note how you can draw relative to the current size:

JPanel center = new JPanel() {

    private static final int N = 256;
    private static final String S = "Todo...";

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        int dx = (getWidth() - g.getFontMetrics().stringWidth(S)) / 2;
        int dy = getHeight() / 2;
        g.drawString(S, dx, dy);
    }

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

You can construct your button names like this:

for (int i = 0; i < 26; i++) {
    String letter = String.valueOf((char) (i + 'A'));
    buttons[i] = new JButton(letter);
    north.add(buttons[i]);
}

Make your panels instance variables and start on the event dispatch thread:

EventQueue.invokeLater(new Runnable() {

    @Override
    public void run() {
        Hangman frame = new Hangman();
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
        frame.add(frame.north, BorderLayout.NORTH);
        frame.add(frame.center, BorderLayout.CENTER);
        frame.add(frame.south, BorderLayout.SOUTH);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }
});

回答2:

This problem is pretty well documented if you do some research - it seems all the panels (besides the CENTER one) aren't recalculated when resized. See How do I make this FlowLayout wrap within its JSplitPane? and http://www.velocityreviews.com/forums/t608472-wrap-flowlayout.html

But for a really quick fix, try changing your main method to this... (basically using a BoxLayout as your main container)

public static void main(String[] args) 
{
    TempProject frame = new TempProject();
    Box mainPanel = Box.createVerticalBox();
    frame.setContentPane(mainPanel);
    mainPanel.add(panel);
    mainPanel.add(panel2);
    mainPanel.add(panel3);
    frame.pack();
    frame.setVisible(true);
}

来源：https://stackoverflow.com/questions/12023334/flowlayout-on-top-of-gridlayout-not-working

标签

java

swing

jframe

jpanel

layout-manager