1 package ui.cfg;
2
3 import java.awt.BorderLayout;
4 import java.awt.FlowLayout;
5
6 import javax.swing.JButton;
7 import javax.swing.JFrame;
8 import javax.swing.JPanel;
9 import javax.swing.JTabbedPane;
10
11 import util.FrameUtil;
12
13 public class FrameConfig
extends JFrame{
14
15 private JButton btnOk =
new JButton("确定"
);
16
17 private JButton btnContrl =
new JButton("取消"
);
18
19 private JButton btnUser =
new JButton("应用"
);
20
21 public FrameConfig() {
22 //设置布局管理器为“边界布局”
23 this.setLayout(
new BorderLayout());
24 //添加主面板
25 this.add(createMainPanel(),BorderLayout.CENTER);
26 //添加按钮面板
27 this.add(
this.createButtonPanel(),BorderLayout.SOUTH);
28 this.setSize(512, 256
);
29 //居中
30 FrameUtil.setFrameCenter(
this);
31 //TODO测试用
32 this.setDefaultCloseOperation(3
);
33 this.setVisible(
true);
34 }
35
36 /**
37 * 创建按钮面板
38 */
39 private JPanel createButtonPanel() {
40 //创建按钮面板，流式布局
41 JPanel jp =
new JPanel(
new FlowLayout(FlowLayout.RIGHT));
42 jp.add(
this.btnOk);
43 jp.add(
this.btnContrl);
44 jp.add(
this.btnUser);
45 return jp;
46 }
47
48 /**
49 * 创建主面板
50 * @return
51 */
52 private JTabbedPane createMainPanel() {
53 return null;
54 }
55
56 public static void main(String[] args) {
57 new FrameConfig();
58 }
59 }
源码如上，下面是报错：
Exception
in thread "main" java.lang.NullPointerException
at java.awt.Container.addImpl(Unknown Source) at java.awt.Container.add(Unknown Source) at javax.swing.JFrame.addImpl(Unknown Source) at java.awt.Container.add(Unknown Source) at ui.cfg.FrameConfig.<init>(FrameConfig.java:25) at ui.cfg.FrameConfig.main(FrameConfig.java:57)找了十多分钟，终于发现 private JTabbedPane createMainPanel(){ return null; } 这个方法的renturn出错了，不应该return null，而应该return new JTabbedPane()才对，改完之后运行就没问题了。
转载于:https://www.cnblogs.com/1314520O/p/10785019.html
