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下面的 SSCCE 是一个扩展JPanel. 是日历的JPanel基本轮廓（为简单起见，我将其剥离了），它由JButton组件 aJLabel和 a组成JTable。当我将此框架添加到窗口（即JDialog）时，它会正常显示。但是，当我用它添加另一个组件时，它就会消失。为什么会发生这种情况，我怎样才能不发生这种情况？

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

public class CalendarPanel extends JPanel {

    private static JDialog dialog = new JDialog();

    public static void main(String[] args) {

    setDialogProperties();
    addComponentsToDialog();
    dialog.setVisible(true);
    }

    private static void setDialogProperties() {
    dialog.setModal(true);
    dialog.setResizable(false);
    dialog.setSize(new Dimension(330, 400));
    dialog.setDefaultCloseOperation(2);
    dialog.setLocationRelativeTo(null);
    }

    private static void addComponentsToDialog() {
    CalendarPanel calendar = new CalendarPanel();
    JPanel panel = new JPanel();
    panel.add(calendar);

    dialog.add(panel);
    //dialog.add(new JLabel("Hello"));
    }

    private static final long serialVersionUID = 1L;
    private JLabel lblMonth;
    private JButton btnPrev, btnNext;
    private JTable tblCalendar;
    private DefaultTableModel mtblCalendar;
    private JScrollPane stblCalendar;
    private static GridBagLayout gridBag = new GridBagLayout();
    private GridBagConstraints constraints = new GridBagConstraints();

    public CalendarPanel() {

    super(gridBag);

    createControls();
    addControlsToPanel();
    addHeaders();
    setTableProperties();
    }

    private void createControls() {
    lblMonth = new JLabel("January");
    btnPrev = new JButton("<");
    btnNext = new JButton(">");
    mtblCalendar = new DefaultTableModel() {

        public boolean isCellEditable(int rowIndex, int mColIndex) {
        return false;
        }
    };
    tblCalendar = new JTable(mtblCalendar);
    stblCalendar = new JScrollPane(tblCalendar);
    stblCalendar.setPreferredSize(new Dimension(300, 247));
    }

    private void addControlsToPanel() {
    GridBagLayout topGridBag = new GridBagLayout();

    JPanel topPanel = new JPanel(topGridBag);

    JPanel labelPanel = new JPanel();
    labelPanel.add(lblMonth);
    labelPanel.setPreferredSize(new Dimension(180, 20));

    constraints.gridx = 1;
    topGridBag.setConstraints(labelPanel, constraints);

    constraints.gridx = 2;
    topGridBag.setConstraints(btnNext, constraints);

    topPanel.add(btnPrev);
    topPanel.add(labelPanel);
    topPanel.add(btnNext);

    gridBag.setConstraints(topPanel, constraints);

    constraints.gridy = 1;
    gridBag.setConstraints(stblCalendar, constraints);

    this.add(topPanel);
    this.add(stblCalendar);
    }

    private void addHeaders() {
    String[] headers = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
    for (int i = 0; i < 7; i++) {
        mtblCalendar.addColumn(headers[i]);
    }
    }

    private void setTableProperties() {
    tblCalendar.getTableHeader().setReorderingAllowed(false);

    tblCalendar.setRowHeight(38);
    mtblCalendar.setColumnCount(7);
    mtblCalendar.setRowCount(6);
    }
}
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1 回答 1

4

JDialogs 和所有顶级窗口默认使用 BorderLayout。当您在未指定位置的情况下向其添加组件（实际上是其 contentPane）时，默认情况下将其添加到 BorderLayout.CENTER 位置。每当您添加一个新组件时，您就是在掩盖之前添加的组件。您将想要了解可供您使用的布局，然后充分利用它们。

例如， 

  dialog.add(panel);
  dialog.add(new JLabel("Hello", SwingConstants.CENTER), BorderLayout.SOUTH);
}

接下来，您将要避免设置任何内容的大小，并确保pack()您的顶级窗口允许这样做。

于 2013-02-26T02:58:00.583 回答