java为什么GridBagLayout认为我的组件不适合容器？

Question

GridBagLayout的行为似乎很奇怪，但在某些非常特定的条件下-是否有人可以在以下条件下运行附加的代码，并解释朝向窗口底部的页面预览面板的大小调整行为：

1. 运行代码-不要在顶部输入名称-在微调器上按住单元格的“向上”按钮，直到页面预览更改为一页-预览不应该（也不会调整大小）
2. 再次运行代码-在“名称”字段中输入“Hello World”（或以大写字母开头的任意两个单词）-按住微调器上单元格的向上按钮，直到页面预览更改为一页-预览的大小调整为不适合窗口并干扰按钮

为什么布局管理器似乎认为页面预览不再合适？setBreaks（）方法没有触及它的维度。为什么在文本字段中输入的字符串的性质会影响这一点

如果在PagePreview类中未重写getWidth（）和getHeight（）方法，则此行为更为明显

抱歉，这不是一个较短的SSCCE，但如果没有完整的代码，我无法复制此问题

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSpinner;
import javax.swing.SpinnerModel;
import javax.swing.SpinnerNumberModel;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

import javax.swing.JSpinner.DefaultEditor;
import javax.swing.JTextField;
import javax.swing.border.BevelBorder;

@SuppressWarnings("serial")
public class ResizeProblem extends JDialog implements ActionListener {

public static void main(String[] args) {

    new ResizeProblem(100, 75);

}

private int designWidth;
private int designHeight;

private JLabel nameLbl;
private JTextField nameField;
private JLabel printDesignLbl;
private JCheckBox printDesign;

private static final double PAGE_RATIO = 0.68;
private static final int PORTRAIT_ACROSS = 40;
private static final int LANDSCAPE_ACROSS = 60;
private int acrossValue;
private int downValue;
private boolean isPortrait;
private JLabel portraitLbl;
private JCheckBox portrait;
private JLabel landscapeLbl;
private JCheckBox landscape;

private JLabel acrossLbl;
private JSpinner across;
private JLabel downLbl;
private JTextField down;
private JLabel info;
private PagePreview preview;
private JButton print;

public ResizeProblem(int designWidth,
        int designHeight) {
    this.designWidth = designWidth;
    this.designHeight = designHeight;
    if (designWidth > designHeight) {
        isPortrait = false;
        acrossValue = LANDSCAPE_ACROSS;
        downValue = PORTRAIT_ACROSS;
    } else {
        isPortrait = true;
        acrossValue = PORTRAIT_ACROSS;
        downValue = LANDSCAPE_ACROSS;
    }
    setTitle("Print Options");
    setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    setModal(true);
    setModalityType(ModalityType.APPLICATION_MODAL);
    setLayout(new GridBagLayout());
    Format format = new Format();
    nameLbl = new JLabel("Project name (optional):");
    add(nameLbl, format.gbc_lw1);
    nameField = new JTextField();
    add(nameField, format.gbc_cw2);
    format.nextLine();

    printDesignLbl = new JLabel("Print design image:");
    add(printDesignLbl, format.gbc_lw2);
    printDesign = new JCheckBox();
    printDesign.setSelected(true);
    add(printDesign, format.gbc_rw1);
    format.nextLine();

    portraitLbl = new JLabel("Print design in portrait:");
    add(portraitLbl, format.gbc_lw2);
    portrait = new JCheckBox();
    portrait.setSelected(isPortrait);
    portrait.setActionCommand("portrait");
    portrait.addActionListener(this);
    add(portrait, format.gbc_rw1);
    format.nextLine();

    landscapeLbl = new JLabel("Print design in landscape:");
    add(landscapeLbl, format.gbc_lw2);
    landscape = new JCheckBox();
    landscape.setSelected(!isPortrait);
    landscape.setActionCommand("landscape");
    landscape.addActionListener(this);
    add(landscape, format.gbc_rw1);
    format.nextLine();

    acrossLbl = new JLabel("Number of cells printed across per page:");
    add(acrossLbl, format.gbc_lw2);
    SpinnerModel model = new SpinnerNumberModel(acrossValue, 20, 150, 1);
    across = new JSpinner(model);
    acrossValue = (int) across.getValue();
    downValue = getDownValue();
    across.addChangeListener(new ChangeListener() {
        @Override
        public void stateChanged(ChangeEvent arg0) {
            acrossValue = (int) across.getValue();
            downValue = getDownValue();
            down.setText(downValue + "");
            info.setText(getInfo());
            if (acrossValue <= designWidth || downValue <= designHeight) {
                preview.setBreaks(acrossValue, downValue);
            }
            repaint();
        }
    });
    ((DefaultEditor) across.getEditor()).getTextField().setEditable(false);
    ((DefaultEditor) across.getEditor()).getTextField().setHorizontalAlignment(JLabel.LEADING);
    ((DefaultEditor) across.getEditor()).getTextField().setHighlighter(null);
    add(across, format.gbc_rw1);
    format.nextLine();
    downLbl = new JLabel("Corresponding printed down:");
    add(downLbl, format.gbc_lw2);
    down = new JTextField();
    down.setText(getDownValue() + "");
    down.setEditable(false);
    down.setCursor(null);
    down.setHighlighter(null);
    add(down, format.gbc_rw1);
    format.nextLine();

    info = new JLabel(getInfo());
    add(info, format.gbc_fulll);
    format.nextLine();

    preview = new PagePreview(designWidth, designHeight);
    preview.setBorder(new BevelBorder(BevelBorder.RAISED));
    preview.setBreaks(acrossValue, downValue);
    add(preview, format.gbc_fullc);
    format.nextLine();

    print = new JButton("Print");
    print.setActionCommand("print");
    print.addActionListener(this);
    add(print, format.gbc_fullc);
    format.nextLine();
    add(new JLabel(), format.gbc_fullc);
    pack();
    setLocationRelativeTo(null);
    setResizable(false);
    setVisible(true);
}

private int getDownValue() {
    int acrossValue = (int) across.getValue();
    if (isPortrait) {
        return (int) Math.ceil(acrossValue / PAGE_RATIO);
    } else {
        return ((int) (acrossValue * PAGE_RATIO));
    }
}

private String getInfo() {
    int pages = (getPagesAcross() * getPagesDown());
    if (pages > 1) {
        return "Design will be printed over " + pages + " pages";
    } else {
        return "Design will be printed on 1 page";
    }
}

private int getPagesAcross() {
    double pages = ((double) designWidth) / acrossValue;
    return (int) Math.ceil(pages);
}

private int getPagesDown() {
    double pages = ((double) designHeight) / downValue;
    return (int) Math.ceil(pages);
}

private void print() {
    dispose();
}

private void swapValues() {
    int temp = acrossValue;
    acrossValue = downValue;
    downValue = temp;
    across.setValue(acrossValue);
    down.setText(downValue + "");
    preview.setBreaks(acrossValue, downValue);
}

@Override
public void actionPerformed(ActionEvent event) {
    if (event.getActionCommand().equals("portrait")) {
        landscape.setSelected(false);
        isPortrait = true;
        swapValues();
    } else if (event.getActionCommand().equals("landscape")) {
        portrait.setSelected(false);
        isPortrait = false;
        swapValues();
    } else if (event.getActionCommand().equals("print")) {
        print();
    }
}

class Format {

    GridBagConstraints gbc_lw1;
    GridBagConstraints gbc_lw2;
    GridBagConstraints gbc_cw2;
    GridBagConstraints gbc_rw1;
    GridBagConstraints gbc_fulll;
    GridBagConstraints gbc_fullc;

    Format() {
        Insets insets = new Insets(20, 20, 0, 20);
        gbc_lw1 = new GridBagConstraints();
        gbc_lw1.gridx = 0;
        gbc_lw1.gridy = 0;
        gbc_lw1.gridwidth = 1;
        gbc_lw1.weightx = 0;
        gbc_lw1.weighty = 0;
        gbc_lw1.anchor = GridBagConstraints.LINE_START;
        gbc_lw1.fill = GridBagConstraints.NONE;
        gbc_lw1.insets = insets;
        gbc_lw2 = new GridBagConstraints();
        gbc_lw2.gridx = 0;
        gbc_lw2.gridy = 0;
        gbc_lw2.gridwidth = 2;
        gbc_lw2.weightx = 0;
        gbc_lw2.weighty = 0;
        gbc_lw2.anchor = GridBagConstraints.LINE_START;
        gbc_lw2.fill = GridBagConstraints.NONE;
        gbc_lw2.insets = insets;
        gbc_cw2 = new GridBagConstraints();
        gbc_cw2.gridx = 1;
        gbc_cw2.gridy = 0;
        gbc_cw2.gridwidth = 2;
        gbc_cw2.weightx = 1;
        gbc_cw2.weighty = 0;
        gbc_cw2.anchor = GridBagConstraints.LINE_END;
        gbc_cw2.fill = GridBagConstraints.HORIZONTAL;
        gbc_cw2.insets = insets;
        gbc_rw1 = new GridBagConstraints();
        gbc_rw1.gridx = 2;
        gbc_rw1.gridy = 0;
        gbc_rw1.gridwidth = 1;
        gbc_rw1.weightx = 1;
        gbc_rw1.weighty = 0;
        gbc_rw1.anchor = GridBagConstraints.LINE_END;
        gbc_rw1.fill = GridBagConstraints.HORIZONTAL;
        gbc_rw1.insets = insets;
        gbc_fulll = new GridBagConstraints();
        gbc_fulll.gridx = 0;
        gbc_fulll.gridy = 0;
        gbc_fulll.gridwidth = 3;
        gbc_fulll.weightx = 1;
        gbc_fulll.weighty = 0;
        gbc_fulll.anchor = GridBagConstraints.LINE_START;
        gbc_fulll.fill = GridBagConstraints.NONE;
        gbc_fulll.insets = insets;
        gbc_fullc = new GridBagConstraints();
        gbc_fullc.gridx = 0;
        gbc_fullc.gridy = 0;
        gbc_fullc.gridwidth = 3;
        gbc_fullc.weightx = 1;
        gbc_fullc.weighty = 1;
        gbc_fullc.anchor = GridBagConstraints.CENTER;
        gbc_fullc.fill = GridBagConstraints.NONE;
        gbc_fullc.insets = insets;
    }

    void nextLine() {
        gbc_lw1.gridy++;
        gbc_lw2.gridy++;
        gbc_cw2.gridy++;
        gbc_rw1.gridy++;
        gbc_fulll.gridy++;
        gbc_fullc.gridy++;
    }

}

class PagePreview extends JPanel {

    private static final int BORDER = 10;

    private int width;
    private int height;
    private int designWidth;
    private int designHeight;
    private int xbreak;
    private int ybreak;

    public PagePreview(int designWidth, int designHeight) {
        this.designWidth = designWidth;
        this.designHeight = designHeight;
        width = designWidth + (BORDER * 2);
        height = designHeight + (BORDER * 2);
        setPreferredSize(new Dimension(width, height));
        setBackground(Color.WHITE);
    }

    @Override
    public int getWidth() {
        return width;
    }

    @Override
    public int getHeight() {
        return height;
    }

    public void setBreaks(int xbreak, int ybreak) {
        this.xbreak = xbreak;
        this.ybreak = ybreak;
        repaint();
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.LIGHT_GRAY);
        g2d.drawRect(BORDER - 1, BORDER - 1, designWidth, designHeight);
        g2d.fillRect(BORDER - 1, BORDER - 1, designWidth, designHeight);
        if (xbreak > 0 && ybreak > 0) {
            g2d.setColor(Color.BLACK);
            int breakpoint = xbreak;
            while (breakpoint < designWidth) {
                g2d.drawLine(BORDER + breakpoint, 0, BORDER + breakpoint, height);
                breakpoint += xbreak;
            }
            breakpoint = ybreak;
            while (breakpoint < designHeight) {
                g2d.drawLine(0, BORDER + breakpoint, width, BORDER + breakpoint);
                breakpoint += ybreak;
            }
        }
    }

}

}