Question

我包含了我的代码。变量fnh是用类范围声明的（在类定义之后）。然而，我不能用最后的陈述打印出来。如果放在actionPerformed方法内部，它会打印变量的值，但不在其外部。可能是什么问题？任何及时的建议将不胜感激。

public class Lamp  {
   int fnh;
   Lamp()  {
     // More code here

  String[] numberOfRunners = { "8", "9", "10", "11", "12",
                                "13", "14", "15", "16", "17",
                                "18", "19", "20", "21", "22" };

   runners = new JComboBox( numberOfRunners );
   runners.setMaximumRowCount(5);        
   runners.addActionListener( new ActionListener() {
        @Override
        public void actionPerformed( ActionEvent ae ) {
           String  runnersNumber = ( String )runners.getSelectedItem();
           fnh = Integer.parseInt( runnersNumber );           
           reducedFNH = reduce( fnh );
       }}
   );     
   middle.add( runners );
   System.out.println( fnh );

    // More code here

}

//更多代码

}课程结束

Answer 1

最后遗失}。

我给过的最简单的答案:-D

Answer 2

问题是fnh的值在您想要打印时仍为空。第一次获取值是在actionperfomed方法中。

Answer 3

您注册了actionListener，然后输出fnh。它还没有改变，因为没有执行任何动作，因此没有调用你的监听器。

也许这样容易理解：

public class Lamp  {
   int fnh;
   ...

   private ActionListener actionListener = new ActionListener() {
       @Override
       public void actionPerformed( ActionEvent ae ) {
          // This is only called, when user performs an action on runners
          String  runnersNumber = ( String )runners.getSelectedItem();
          fnh = Integer.parseInt( runnersNumber );
      }};

    public Lamp()  {
        ...
        runners = new JComboBox(numberOfRunners);
        runners.addActionListener(actionListener);
        System.out.println( fnh );
    }
}

隐藏在actionperformed中的全局变量

3 个答案: