Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException

Question

我的代码如下：
JTabbedDemo.java

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

public class JTabbedDemo
{
public static void main(String[] args) throws Exception
{

    //显示外观风格
    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

    JFrame jframe=new JFrame("奖金状况");
    jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    jframe.setVisible(true);

    JTabbedPane tp=new JTabbedPane();//创建一个选项卡容器，将之添加到顶层容器内
    jframe.setContentPane(tp);

    JPanel panel1=new JPanel();
    JPanel panel2=new JPanel();
    JPanel panel3=new JPanel();
    JPanel panel4=new JPanel();
    JPanel panel5=new JPanel();

    //添加选项卡容器，并且设置其中每个选项卡的标签以及其是否可启用。
    tp.addTab("panel1",panel1);
    tp.setEnabledAt(0,true);
    tp.setTitleAt(0,"个人收入状况");

    tp.addTab("panel2",panel2);
    tp.setEnabledAt(1,true);
    tp.setTitleAt(1,"工资");

    tp.addTab("panel2",panel3);
    tp.setEnabledAt(2,true);
    tp.setTitleAt(2,"奖金");

    tp.addTab("panel3",panel4);
    tp.setEnabledAt(3,true);
    tp.setTitleAt(3,"津贴");

    tp.addTab("panel4",panel5);
    tp.setEnabledAt(4,true);
    tp.setTitleAt(4,"社保");

    //设置其大小以及其选项卡的位置方向
    tp.setPreferredSize(new Dimension(800,600));
    tp.setTabPlacement(JTabbedPane.TOP);

    //设置选项卡在容器内的显示形式
    tp.setTabLayoutPolicy(JTabbedPane.SCROLL_TAB_LAYOUT);
    jframe.pack();

    //创建8个标签组件，将5个中间窗口设置为流布局，并且将标签组件分别放入到其中
    JLabel l1=new JLabel("工资状况");
    JLabel l2=new JLabel("3000元/月");
    JLabel l3=new JLabel("奖金状况");
    JLabel l4=new JLabel("1500元/月");
    JLabel l5=new JLabel("津贴状况");
    JLabel l6=new JLabel("500元/月");
    JLabel l7=new JLabel("社保状况");
    JLabel l8=new JLabel("200元/月");

    panel2.setLayout(new FlowLayout());
    panel3.setLayout(new FlowLayout());
    panel4.setLayout(new FlowLayout());
    panel5.setLayout(new FlowLayout());

    panel2.add(l1);
    panel2.add(l2);
    panel3.add(l3);
    panel3.add(l4);
    panel4.add(l5);
    panel4.add(l6);
    panel5.add(l7);
    panel5.add(l8);

    jframe.pack();

}

}

错误信息如下：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.basic.BasicTabbedPaneUI.calculateTabWidth(Unknown So
urce)
at javax.swing.plaf.basic.BasicTabbedPaneUI$TabbedPaneLayout.calculateTa
bRects(Unknown Source)
at javax.swing.plaf.basic.BasicTabbedPaneUI$TabbedPaneLayout.calculateLa
youtInfo(Unknown Source)
at javax.swing.plaf.basic.BasicTabbedPaneUI$TabbedPaneLayout.layoutConta
iner(Unknown Source)
at java.awt.Container.layout(Unknown Source)
at java.awt.Container.doLayout(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validate(Unknown Source)
at javax.swing.RepaintManager.validateInvalidComponents(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Sour
ce)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

tp.setTabLayoutPolicy(JTabbedPane.SCROLL_TAB_LAYOUT);
这句话有问题，你注释掉就没异常了，我对swing不是很了解，应该是你这种写法有问题，你看看吧，希望对你有帮助 :)