border - LineBordersのマージン

Question

LineBorderを使用してJTextAreaを作成し、テキストとLineBorderの間に少しパディングを残したいと思います。

これは標準クラスで可能ですか、それともカスタムの「DoubleLine」境界線（1つは色付き、もう1つは余白付き）が必要ですか？

いくつかのサンプルコードを以下に示します...

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Insets;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
import javax.swing.JTextArea;
import javax.swing.SwingConstants;
import javax.swing.SwingUtilities;
import javax.swing.border.Border;
import javax.swing.border.LineBorder;

public class TextAreaLineBorder extends JFrame
{
    private static final long   serialVersionUID    = 1L;

    private class MyPanel extends JPanel
    {

        private static final long   serialVersionUID    = 1L;

        public MyPanel()
        {
            setLayout(new FlowLayout());

            JTextArea ta = new JTextArea("Some text");
            ta.setSize(200, 50);

            boolean useDefaultBorder = false;

            if (useDefaultBorder)
            {
                // Setting the margin works fine, with the default border
                ta.setMargin(new Insets(12, 12, 12, 12));

                Border b = ta.getBorder();
                Insets defaultInsets = b.getBorderInsets(ta);
                System.out.println("Default Insets: "
                        + defaultInsets);

            }
            else
            {
                 // Try using a non-default LineBorder
                 LineBorder lb = (LineBorder) BorderFactory.createLineBorder(Color.YELLOW, 2);
                 ta.setBorder(lb);

                 // TODO: What should be done so that the LineBorder has Insets?
                 ta.setMargin(new Insets(12, 12, 12, 12));

                 Insets lineBorderInsets = lb.getBorderInsets(ta);
                 System.out.println("LineBorder Insets: " + lineBorderInsets);
            }
            add(ta);
        }
    }

    public TextAreaLineBorder()
    {
        setResizable(true);

        setName(getClass().getSimpleName());
        setTitle("My Frame");
        setSize(300, 300);

        JTabbedPane tabbedPane = new JTabbedPane(SwingConstants.TOP);

        // Add the panel
        tabbedPane.addTab("Button panel", new MyPanel());

        add(tabbedPane, BorderLayout.CENTER);

        getContentPane().add(tabbedPane);
    }

    private static void createAndShowGUI()
    {
        // Create and set up the window.
        TextAreaLineBorder frame = new TextAreaLineBorder();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }

    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                try
                {
                    createAndShowGUI();
                }
                catch (Exception e)
                {
                    e.printStackTrace();
                    System.exit(0);
                }
            }
        });
    }

}

Answer 1

この問題を解決するのに役立つクラスを作成しました。おそらく、すべての JTextComponent に同じソリューションを使用できます。

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Date;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.border.Border;
import javax.swing.border.CompoundBorder;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;

public class JTextAreaWithPaddedBorder extends JTextArea
{
    // **********************************************************************
    // To modify the sample program using GWT Designer, uncomment this code
    // **********************************************************************
    // public JTextAreaWithPaddedBorder()
    // {
    // }
    //
    // /**
    // * Bogus Constructor
    // *
    // * @wbp.parser.constructor (Use this method in the GWT Designer)
    // */
    //
    // public JTextAreaWithPaddedBorder(int ignore)
    // {
    // createAndShowGUI();
    // }
    // **********************************************************************
    // To modify the sample program using GWT Designer, uncomment this code
    // **********************************************************************

    public static void createAndShowGUI()
    {
        // Create and set up the frame
        JFrame frmTextareawithpaddedborder = new JFrame();
        frmTextareawithpaddedborder.setTitle("TextAreaWithPaddedBorder");
        frmTextareawithpaddedborder.setName("frmTextareawithpaddedborder");
        frmTextareawithpaddedborder.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frmTextareawithpaddedborder.setBounds(100, 100, 514, 495);
        frmTextareawithpaddedborder.setResizable(false);

        JPanel contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        frmTextareawithpaddedborder.setContentPane(contentPane);

        JScrollPane scrollPane = new JScrollPane();
        scrollPane.setBounds(5, 5, 490, 395);
        scrollPane.setName("scrollPane");
        contentPane.add(scrollPane);

        final JTextAreaWithPaddedBorder textArea = new JTextAreaWithPaddedBorder();

        textArea.setBorder(new LineBorder(new Color(0, 0, 0), 2));
        textArea.setName("textArea");
        textArea.setLineWrap(true);
        textArea.setWrapStyleWord(true);
        String text = "The iPhone is a line of smartphones designed and marketed by Apple Inc. The first iPhone was unveiled by Steve Jobs, then CEO of Apple, on January 9, 2007,[1] and released on June 29, 2007. The 5th generation iPhone, the iPhone 4S, was announced on October 4, 2011, and released 10 days later.  An iPhone can function as a video camera (video recording was not a standard feature until the iPhone 3GS was released), a camera phone, a portable media player, and an Internet client with email and web browsing capabilities, can send texts and receive visual voicemail, and has both Wi-Fi and cellular data (2G and 3G) connectivity. The user interface is built around the device's multi-touch screen, including a virtual keyboard rather than a physical one.";
        textArea.setText(text);
        textArea.append("\n\nThis is the text within the TextArea.  As the border of the TextArea is changed, the text should display properly.");
        contentPane.setLayout(null);
        textArea.setBackground(Color.WHITE);
        scrollPane.setViewportView(textArea);

        btnChangeMargins = new JButton("Change Margins");
        btnChangeMargins.setBounds(13, 430, 152, 23);
        btnChangeMargins.setName("btnChangeMargins");
        btnChangeMargins.addActionListener(new ActionListener()
        {
            @Override
            public void actionPerformed(ActionEvent e)
            {
                long t = (new Date()).getTime() % 100;
                int top = (int) (t * 18) % 15;
                int bottom = (int) (t * 34) % 15;
                int left = (int) (t * 52) % 15;
                int right = (int) (t * 52) % 15;
                Insets insets = new Insets(top, left, bottom, right);
                textArea.setMargin(insets);
            }
        });
        contentPane.add(btnChangeMargins);

        btnChangeBGColor = new JButton("Change BG Color");
        btnChangeBGColor.addActionListener(new ActionListener()
        {
            @Override
            public void actionPerformed(ActionEvent e)
            {
                long t = (new Date()).getTime() % 100;
                int r = 100 + (int) (t * 18) % 100;
                int g = 100 + (int) (t * 34) % 100;
                int b = 100 + (int) (t * 52) % 100;
                Color c = new Color(r, g, b);
                textArea.setBackground(c);
            }
        });

        btnChangeBGColor.setBounds(178, 430, 152, 23);
        btnChangeBGColor.setName("btnChangeBGColor");
        contentPane.add(btnChangeBGColor);

        btnChangeBorder = new JButton("Change Border");
        btnChangeBorder.setBounds(343, 430, 152, 23);
        btnChangeBorder.setName("btnChangeBorder");
        btnChangeBorder.addActionListener(new ActionListener()
        {
            int last    = 0;

            @Override
            public void actionPerformed(ActionEvent e)
            {
                Border nextBorder;
                switch (last++ % 8)
                {
                    case 0:
                        nextBorder = BorderFactory.createLoweredBevelBorder();
                        break;

                    case 1:
                        nextBorder = BorderFactory.createEmptyBorder();
                        break;
                    case 2:
                        nextBorder = BorderFactory.createEtchedBorder();
                        break;
                    case 3:
                        nextBorder = BorderFactory.createLineBorder(Color.black, 2);
                        break;
                    case 4:
                        nextBorder = BorderFactory.createRaisedBevelBorder();
                        break;
                    case 5:
                        nextBorder = BorderFactory.createCompoundBorder(BorderFactory.createLineBorder(Color.red, 3), BorderFactory
                                .createLoweredBevelBorder());
                        break;
                    case 6:
                        nextBorder = BorderFactory.createMatteBorder(2, 15, 1, 15, new Color(255, 0, 0));
                        break;
                    case 7:
                        nextBorder = BorderFactory.createTitledBorder("Titled Border");
                        break;

                    default:
                        nextBorder = BorderFactory.createTitledBorder("Titled Border");

                }

                textArea.setBorder(nextBorder);
            }
        });
        contentPane.add(btnChangeBorder);
        frmTextareawithpaddedborder.setVisible(true);
    }

    private static final long   serialVersionUID    = 1L;
    private static JButton      btnChangeMargins;
    private static JButton      btnChangeBGColor;
    private static JButton      btnChangeBorder;

    @Override
    public void setBorder(Border border)
    {
        int paddingWidth = 0;

        Border currentBorder = getBorder();
        if (currentBorder != null)
        {
            // The padding width will be the minimum width specified in the insets
            Insets insets = getMargin();
            paddingWidth = Math.min(insets.bottom, insets.top);
            paddingWidth = Math.min(paddingWidth, insets.left);
            paddingWidth = Math.min(paddingWidth, insets.right);
        }
        /*
         * Use a LineBorder for the padding.
         * 
         * The color must be the same as the background color of the TextComponent
         */
        super.setBorder(new CompoundBorder(border, BorderFactory.createLineBorder(getBackground(), paddingWidth)));
    }

    @Override
    public void setBackground(Color c)
    {
        super.setBackground(c);
        Border b = getBorder();
        if (b != null)
        {
            setBorder(((CompoundBorder) b).getOutsideBorder());
        }
    }

    @Override
    public void setMargin(Insets m)
    {
        super.setMargin(m);
        Border b = getBorder();
        if (b != null)
        {
            setBorder(((CompoundBorder) b).getOutsideBorder());
        }
    }

    /**
     * Launch the application.
     */
    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                try
                {
                    createAndShowGUI();
                }
                catch (Exception e)
                {
                    e.printStackTrace();
                }
            }
        });
    }

}