的NullPointerException）一個事件的actionPerformed

-2

我具有在JTextField.getText（一個的NullPointerException）內一個內的actionPerformed事件：的NullPointerException）一個事件的actionPerformed

import javax.swing.*; 

public class myForm extends JInternalFrame 
{ 
    private JTextField txtName; 
    private String name; 

    public myForm() 
    { 
     super("My Form", true, true, true, true); 

     txtName = new JTextField(); 

     JButton button = new JButton("button"); 

     button.addActionListener(new ActionListener() 
     { 
      public void actionPerformed(ActionEvent e) 
      { 
       name = txtName.getText(); // here is the NullPointerException 
      } 
     } 
    } 
}

這裏是堆跟蹤：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException 
    at ContatoFormulario$1.actionPerformed(ContatoFormulario.java:80) 
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995) 
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318) 
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387) 
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242) 
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236) 
    at java.awt.Component.processMouseEvent(Component.java:6216) 
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3265) 
    at java.awt.Component.processEvent(Component.java:5981) 
    at java.awt.Container.processEvent(Container.java:2041) 
    at java.awt.Component.dispatchEventImpl(Component.java:4583) 
    at java.awt.Container.dispatchEventImpl(Container.java:2099) 
    at java.awt.Component.dispatchEvent(Component.java:4413) 
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4556) 
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4220) 
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4150) 
    at java.awt.Container.dispatchEventImpl(Container.java:2085) 
    at java.awt.Window.dispatchEventImpl(Window.java:2475) 
    at java.awt.Component.dispatchEvent(Component.java:4413) 
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:599) 
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) 
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) 
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) 
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) 
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) 
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

任何人有想法嗎？我已經嘗試通過網絡搜索並沒有找到任何解決方案。

此問題時更頻當我們重新實例化JTextField的是這樣的：

public class myForm extends JInternalFrame 
{ 
    private JTextField txtName; 

    public myForm() 
    { 
     JTextField txtName = new JTextField();   
    } 
}

但這種情況並非如此，任何想法？

來源

2010-12-04 charles.art.br

你的第一個例子是不可編譯的，因爲你有一個無效的addActionListener（）方法的語法，並且你永遠不會實際添加按鈕到框架，所以它不應該觸發一個ActionEvent。我們需要看到實際的代碼來幫助你。 – 2010-12-04 21:47:27

第一段代碼不應該。您是否刪除了某些內容，或者弄糊塗了您編譯的內容？

第二段代碼有局部變量隱藏字段。

來源

2010-12-04 21:35:30

我同意。該錯誤不在您向我們展示的代碼中。 – 2010-12-04 21:35:54

的NullPointerException）一個事件的actionPerformed

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