renturn 错误 

 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。

posted @ 2019-04-28 16:59  风飘无殇  阅读(212)  评论(0)  编辑  收藏  举报
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