1

我什至不知道要问什么，只能发布代码并将错误消息放在这里。该程序应该创建一个带有两个选项卡的窗口，每个选项卡中都有一个分数表。

package components;

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

public class TopLevelDemo extends JPanel{
    public TopLevelDemo() {
        JTabbedPane tabbedPane = new JTabbedPane();
        String[] players = new String[4];
        Object[][] singlesScores = new Object[2][4];
        Object[][] doublesScores = new Object[2][4];
        createScores(singlesScores);
        createScores(doublesScores);

        JComponent panel1 = makeScoreTable(singlesScores, players, 0, 0);
        tabbedPane.addTab("Singles",panel1);
        tabbedPane.setMnemonicAt(0, KeyEvent.VK_1);

        JComponent panel2 = makeScoreTable(doublesScores, players, 0, 0);
        tabbedPane.addTab("Doubles", panel2);
        tabbedPane.setMnemonicAt(1, KeyEvent.VK_2);

        add(tabbedPane);
        tabbedPane.setTabLayoutPolicy(JTabbedPane.SCROLL_TAB_LAYOUT);
    }
    protected JComponent makeScoreTable(Object[][] scores, String[] players, int x, int y) {
        JPanel panel = new JPanel(true);
        JTable table = new JTable(scores, players);
        GridBagConstraints c = new GridBagConstraints();
        c.gridx=x;
        c.gridy=y;
        panel.add(table, c);
        return panel;
    }
    protected JComponent makeTextPanel(String text) {
        JPanel panel = new JPanel(true);
        JLabel filler = new JLabel(text);
        filler.setHorizontalAlignment(JLabel.CENTER);
        panel.setLayout(new GridLayout(10, 25));
        panel.add(filler);
        return panel;
    }
    private static void createAndShowGUI() {
        JFrame frame = new JFrame("TopLevelDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.add(new TopLevelDemo(), BorderLayout.CENTER);
        frame.pack();
        frame.setVisible(true);
    }
     private Object[][] createScores(Object[][] scores) {
        scores[0][0]= new String("Home");
        scores[0][1]= new Integer(0);
        scores[0][2]= new Integer(0);
        scores[0][3]= new Integer(0);
        scores[1][0]= new String("Away");
        scores[0][1]= new Integer(0);
        scores[0][2]= new Integer(0);
        scores[0][3]= new Integer(0);
        return scores;
    }
    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                UIManager.put("swing.boldMetal", Boolean.FALSE);
                createAndShowGUI();
            }
        });
    }
}

然后我得到错误

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at javax.swing.JTable$1.getColumnName(JTable.java:665)
    at javax.swing.JTable.addColumn(JTable.java:2770)
    at javax.swing.JTable.createDefaultColumnsFromModel(JTable.java:1264)
    at javax.swing.JTable.tableChanged(JTable.java:4374)
    at javax.swing.JTable.setModel(JTable.java:3676)
    at javax.swing.JTable.<init>(JTable.java:612)
    at javax.swing.JTable.<init>(JTable.java:553)
    at javax.swing.JTable.<init>(JTable.java:664)
    at components.TopLevelDemo.makeScoreTable(TopLevelDemo.java:30)
    at components.TopLevelDemo.<init>(TopLevelDemo.java:17)
    at components.TopLevelDemo.createAndShowGUI(TopLevelDemo.java:49)
    at components.TopLevelDemo.access$000(TopLevelDemo.java:8)
    at components.TopLevelDemo$1.run(TopLevelDemo.java:68)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:666)
    at java.awt.EventQueue.access$400(EventQueue.java:81)
    at java.awt.EventQueue$2.run(EventQueue.java:627)
    at java.awt.EventQueue$2.run(EventQueue.java:625)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:636)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

有人知道我做错了什么或做得不好吗？

4

2 回答 2

2

当 JTable 尝试创建列时，您似乎获得了 NPE，这可以通过以下事实来解释：当您调用它时：

JComponent panel1 = makeScoreTable(singlesScores, players, 0, 0);

玩家数组只包含空字符串。使它们非空。

于 2012-11-03T19:11:39.907 回答
1

您需要为表列名称分配值。

一个字符串数组

String[] players = new String[4];

创建一个 2 s 的数组，String每个数组都有默认值null。你可以使用：

String[] players = { "Player 1", "Player 2", "Player 3", "Player 4" };

更新：

直接在乐谱面板上添加一个JTable不允许显示所有客户区。要修复，您可以将其放在JScrollPane：

panel.add(new JScrollPane(table), c);
于 2012-11-03T19:13:07.627 回答