当我在文本字段上按Enter时，我一直收到错误消息（以下将发帖错误）。我希望文本字段将数据保存到全局定义的变量。每当我的代码中不包含“名称”时，actionListener都可以工作，例如，如果我将int a = 3放入，则没有错误。我也在全局上（在主gui上）声明了名称，因为如果我没有收到错误消息，指出变量不在范围内，也许这是一个问题吗？
//Declared inside the main gui (the others are nested in this)
JTextField name;
JLabel nameLabel;
//Name text field defined inside the gui jInternalFrame
TextField name = new TextField("Enter Name..", 20);
JLabel nameLabel = new JLabel();
nameLabel.setText("Name: ");
name.addActionListener(new nameListener());
addRoomPanel.add(nameLabel);
addRoomPanel.add(name);`
//ActionListener defined outside of the text field gui
class nameListener implements ActionListener{
public void actionPerformed(ActionEvent e){
nameString = name.getText();
name.setText("saved");
name.selectAll();
}
}
ERROR MESSAGE:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at InternalFrame$dobListener.actionPerformed(InternalFrame.java:445)
at java.awt.TextField.processActionEvent(TextField.java:617)
at java.awt.TextField.processEvent(TextField.java:585)
at java.awt.Component.dispatchEventImpl(Component.java:4872)
at java.awt.Component.dispatchEvent(Component.java:4698)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:747)
at java.awt.EventQueue.access$300(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:706)
at java.awt.EventQueue$3.run(EventQueue.java:704)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:720)
at java.awt.EventQueue$4.run(EventQueue.java:718)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:717)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
UI的组件定义了两次。一次在GUI类中作为变量，一次在（我想）构造函数中。由于这两个变量具有namename和nameLabel存在。构造函数将访问在构造函数中声明的变量，因此GUI类的变量保持未初始化（null）。的ActionListener访问的变量在GUI-类，它是null和抛出一个NullPointerException。您将必须使用一个变量而不是两个。为了获得更精确的答案，我需要更多代码（或者至少比上面发布的摘录更有用）。
本文收集自互联网，转载请注明来源。
如有侵权，请联系 [email protected] 删除。
我来说两句