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我将 JTabbedPane 与不同的面板一起使用，并且我将 gridLayout 用于我将添加的按钮数组。我尝试将按钮循环到更简单的代码。但是我得到了一个空指针异常，我不知道我是怎么得到这种错误的。这是我的代码

import javax.swing.*;
import javax.swing.border.CompoundBorder;
import java.awt.*;
public class HotelRoomsGUI extends JPanel{
    private JTabbedPane mainJTP;
    private JPanel classicTab,deluxeTab,presidentialTab,classicSubPanel,deluxeSubPanel,presidentialSubPanel;
    private String classicRoomNo[] = {"101","102","103","104","105","106","107","108","109","101","111","112"};
    private String deluxeRoomNo[] = {"201","202","203","204","205","206","207","208","209","201","211","212"};
    private String presidentialRoomNo[] = {"301","302","303","304","305","306","307","308","309","301","311","312"};
    private JButton[] classicRoom, deluxeRoom, presidentialRoom;
    public HotelRoomsGUI(){

        setLayout(null);
        setBackground(new Color(90,90,90));
        add(tabbedPane());

    }
    public JPanel classic()
    {
        classicTab = new JPanel();
        classicTab.setBackground(new Color(70,70,70));
        classicTab.setLayout(null);
        classicSubPanel();
        return classicTab;
    }
    public JPanel classicSubPanel()
    {
        classicSubPanel = new JPanel();
        classicSubPanel.setBounds(10,10,605,455);
        classicSubPanel.setLayout(new GridLayout(4,3,10,10));
        classicSubPanel.setBackground(new Color(70,70,70));
        classicTab.add(classicSubPanel);
        rooms();
        return classicTab;
    }
    public JPanel deluxe()
    {
        deluxeTab = new JPanel();
        deluxeTab.setBackground(new Color(70,70,70));
        deluxeTab.setLayout(null);
        deluxeSubPanel();
        return deluxeTab;
    }
    public JPanel deluxeSubPanel()
    {
        deluxeSubPanel = new JPanel();
        deluxeSubPanel.setBounds(10,10,605,455);
        deluxeSubPanel.setLayout(new GridLayout(4,3,10,10));
        deluxeSubPanel.setBackground(new Color(70,70,70));
        deluxeTab.add(deluxeSubPanel);
        rooms();
        return deluxeSubPanel;
    }
    public JPanel presidential()
    {
        presidentialTab = new JPanel();
        presidentialTab.setBackground(new Color(70,70,70));
        presidentialTab.setLayout(null);
        presidentialSubPanel();
        return presidentialTab;
    }
    public JPanel presidentialSubPanel()
    {
        presidentialSubPanel = new JPanel();
        presidentialSubPanel.setBounds(10,10,605,455);
        presidentialSubPanel.setLayout(new GridLayout(4,3,10,10));
        presidentialSubPanel.setBackground(new Color(70,70,70));
        presidentialTab.add(presidentialSubPanel);
        rooms();
        return presidentialSubPanel;
    }
    public JTabbedPane tabbedPane()
    {
        UIManager.put("TabbedPane.selected", Color.ORANGE); 
        mainJTP = new JTabbedPane();
        mainJTP.setBackground(Color.WHITE); 
        mainJTP.setBounds(3,1,630,500);
        mainJTP.addTab("Classic",classic());
        mainJTP.addTab("Deluxe",deluxe());
        mainJTP.addTab("Presidential",presidential());
        return mainJTP;
    }
    public void rooms()
    {
        JButton presidentialRoom[] = new JButton[presidentialRoomNo.length];        
        JButton deluxeRoom[] = new JButton[deluxeRoomNo.length];
        JButton classicRoom[] = new JButton[classicRoomNo.length];
        for(int x = 0;x<classicRoomNo.length;x++){
            //classic rooms
            ImageIcon imageC = new ImageIcon("C:\\Users\\John\\workspace\\SystemTest\\src\\Images\\classicRooms.JPG"); // image
            classicRoom[x] = new JButton(classicRoomNo[x],imageC);
            classicRoom[x].setBackground(Color.WHITE);
            classicRoom[x].setBorder(new CompoundBorder(BorderFactory.createEtchedBorder(Color.WHITE,Color.GRAY),
                    BorderFactory.createEtchedBorder(Color.WHITE,Color.GRAY)));
            classicSubPanel.add(classicRoom[x]);
            //deluxe rooms
            ImageIcon imageD = new ImageIcon("C:\\Users\\John\\workspace\\SystemTest\\src\\Images\\deluxeRooms.JPG"); // image
            deluxeRoom[x] = new JButton(deluxeRoomNo[x],imageD);
            deluxeRoom[x].setBackground(Color.WHITE);
            deluxeRoom[x].setBorder(new CompoundBorder(BorderFactory.createEtchedBorder(Color.WHITE,Color.GRAY),
                    BorderFactory.createEtchedBorder(Color.WHITE,Color.GRAY)));
            deluxeSubPanel.add(deluxeRoom[x]);
            //presidential rooms
            ImageIcon imageP = new ImageIcon("C:\\Users\\John\\workspace\\SystemTest\\src\\Images\\presidentialRooms.JPG"); // image
            presidentialRoom[x] = new JButton(deluxeRoomNo[x],imageP);
            presidentialRoom[x].setBackground(Color.WHITE);
            presidentialRoom[x].setBorder(new CompoundBorder(BorderFactory.createEtchedBorder(Color.WHITE,Color.GRAY),
                    BorderFactory.createEtchedBorder(Color.WHITE,Color.GRAY)));
            presidentialSubPanel.add(presidentialRoom[x]);

        }
    }
}

请给我一些提示，告诉我如何编写更清晰、更好的方法

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2 回答 2

2

你在调用时得到一个NullPointerExceptionas deluxeSubPanelhas not been instantiated 调用rooms()时：

deluxeSubPanel.add(deluxeRoom[x]);

作为一般准则，在创建具有依赖组件的组件时最好使用自上而下的方法。这将使创建顺序 - JTabbedPane-JPanel子组件。

于 2012-10-06T10:28:00.240 回答
2

看看我的建议，这是你的tabbedPane()方法：

public JTabbedPane tabbedPane() {
    UIManager.put("TabbedPane.selected", Color.ORANGE);
    mainJTP = new JTabbedPane();
    mainJTP.setBackground(Color.WHITE);
    mainJTP.setBounds(3, 1, 630, 500);
    mainJTP.addTab("Classic", classic());
    mainJTP.addTab("Deluxe", deluxe());
    mainJTP.addTab("Presidential", presidential());
    rooms();  // I've inserted this, no panic!
    return mainJTP;
}

在上面的方法中，如果您仔细跟踪，对方法classic(), deluxe()的调用presidential()已经触发了对方法的调用。rooms()相反，rooms()像我刚才所做的那样打一个电话。删除代码中其他地方的调用rooms()。

于 2012-10-06T10:32:34.593 回答