Question

你好，我有一个例外

    Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at ModelsEvenements.Actions.test(Actions.java:18)
at ModelsEvenements.Designer$GestionActions.actionPerformed(Designer.java:58)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

当我想要访问另一个班级的标签时。标签受到保护，并且类可以正确扩展

设计师：

public class Designer extends JFrame {


private static final long serialVersionUID = 1L;

public JButton btnCounter;
protected JLabel lblNombreClic;
Actions a;

protected int test = 1;


public Designer() {

}

public Designer(String t) {
    super("Essaie Modèle");     
    lblNombreClic = new JLabel("Number of clics " + 0);
    setSize(350, 200);
    JPanel panneau = new JPanel();


    lblNombreClic.setText( "test" );
    btnCounter = new JButton("c");
    btnCounter.setMnemonic('C');
    GestionActions compteurListener = new GestionActions();


    //3-enregistrer le gestionnaire auprès du bouton
    btnCounter.addActionListener(compteurListener);

    panneau.add(btnCounter);
    panneau.add(lblNombreClic);

    setContentPane(panneau); // comme add(panneau)
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    // TODO Auto-generated constructor stub
    a = new Actions();


}

public class GestionActions implements ActionListener {
    @Override
    public void actionPerformed(ActionEvent e) {
        a.test();
    }
}

}

操作：

public class Actions extends Designer{


private static final long serialVersionUID = 1L;

private int counter = 0;

public Actions() {

}

public  void test( ) {
    counter++;
    lblNombreClic.setText( "Number of clics " + counter );

   }
}

编辑：DESIGNER是我的窗户。我从main.cs主文件中提取了一个字符串文本。

当我单击按钮时，它会自动执行测试操作。动作不是无限的，因为它不会再次使用字符串调用构造函数。

它只是向我显示错误。

我希望能够直接在Actions类中使用所有按钮和将来的文本框。

如何修复？

异常“ AWT-EventQueue-0” java.lang.NullPointerException PROTECTED对象

0 个答案: