Dynamically change the width of JDialog

问题

I have created a JDialog which contains a JLabel. Because the length of text, which changes based on users' input, can contain a large number of characters, there is the need to dynamically change the length of the JDialog based on the size of length of the JDialog. I have tried the pack() method but it's not the case for it. Can anyone give me some tips? Thanks in advance!

回答1:

getPreferredSize for JLabel - basically you have to get textLength from JLabel in pixels, there are 3 correct ways, but I love:
```
SwingUtilities.computeStringWidth(FontMetrics fm, String str)
```
Now you are able to setPreferredSize for JLabel correctly (please by defalut is there needed to add +5 - +10 to the Integer that returns SwingUtilities.computeStringWidth)
Call pack(); on the top level container (the JDialog).

回答2:

~~Try invoking validate() on the JDialog.~~ I just realized that this will not work.

Here's a nice thread that discusses this issue. I would recommend listening to the answer and suggestions provided by @Andrew Thompson, who's actually a prominent user here.

回答3:

Another alternative is to put the text into a JTextArea and put that in a JScrollPane.

E.G.

Code

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

class ExpandingText {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                final String s = 
                    "The quick brown fox jumped over the lazy dog.  ";

                final JTextArea textArea = new JTextArea(s,5,30);
                textArea.setWrapStyleWord(true);
                textArea.setLineWrap(true);
                textArea.setEditable(false);
                textArea.setFocusable(false);

                JButton button = new JButton("Add Text");
                button.addActionListener(new ActionListener(){
                        public void actionPerformed(ActionEvent ae) {
                            textArea.append(s);
                        }
                    });

                JPanel panel = new JPanel(new BorderLayout(3,3));
                panel.add(button, BorderLayout.NORTH);
                panel.add(new JScrollPane(textArea), BorderLayout.CENTER);

                JOptionPane.showMessageDialog(null, panel);
            }
        });
    }
}