基本textField actionListener发生错误（命令在侦听器中时发生错误）

Question

I keep getting an error (Will post error below) When I press enter on my text field. I want the text field to save the data to a globally defined variable. The actionListener works whenever I don't include 'name' in my code, for example if I put int a = 3 then there are no errors. I have also declared name globally (on the main gui) because if I don't I get an error saying the variable is not in the scope, maybe this is an issue?

    //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)

Answer 1

The Components of the UI are defined twice. Once in the GUI-class as variables, once in the (i suppose) constructor. Due to this two variables with name name and nameLabel exist. The constructor will access the ones declared in the constructor, thus the variables of the GUI-class remain uninitialized ( null ). The ActionListener access the variable in the GUI-class, which is null and throws a NullPointerException . You'll have to use one variable instead of two. For a more precise answer, i'll need a bit more code (or atleast something more useable than the snippets posted above).