從另一個類中的方法創建actionlistener

Question

嗨，我的代碼到目前為止做了這樣的事情：點擊一個按鈕，打開一個組合框。 我想在ComboBox上選擇一個選項，根據選擇的選項，我想使用getSelectIndex（）打開另一個組合框。

以下是我的代碼的相關部分。 我知道我必須讓其他組合框不可見或被刪除，但此刻我只是想讓組合框出現。 正如你所看到的，我已經為按鈕運行了動作滑動器並打開了組合框。但是當在組合框中選擇一個字符串時，沒有發生任何事件。 但是當我運行它時，沒有出現組合框。

public class Work extends JFrame {
// variables for JPanel

  private JPanel buttonPanel;
  private JButton timeButton;

   public Work() 
 {
       setLayout(new BorderLayout()); 

      buttonPanel = new JPanel();
  buttonPanel.setBackground(Color.RED);
  buttonPanel.setPreferredSize(new Dimension(400, 500));
      add(buttonPanel,BorderLayout.WEST);
      timeButton = new JButton("Time"); 
  buttonPanel.add(timeButton);


  buttontime clickTime = new buttontime(); // event created when time button is clicked
  timeButton.addActionListener(clickTime);

    Time timeObject = new Time();
  timeObject.SelectTime();
  buttontime2 selectDest = new buttontime2();
  timeObject.getAirportBox().addActionListener(selectDest);



   }



       public class buttontime implements ActionListener { //creating actionlistener for clicking on timebutton to bring up a combobox
  public void actionPerformed(ActionEvent clickTime)  {
           Time timeObject = new Time();
           timeObject.SelectTime();
           add(timeObject.getTimePanel(),BorderLayout.EAST);
           timeObject.getTimePanel().setVisible(true); 
           timeObject.getTimePanel().revalidate() ;
           timeObject.getAirportBox().setVisible(true);


  }
  }





          public class buttontime2 implements ActionListener{
  public void actionPerformed(ActionEvent selectDest) {
   Time timeObject = new Time();
  timeObject.SelectTime();


  if(timeObject.getAirportBox().getSelectedIndex() == 1) {



  timeObject.getEastMidBox().setVisible(true);

  }

  else if(timeObject.getAirportBox().getSelectedIndex() == 2) {

  timeObject.getBirmBox().setVisible(true);
 }
  else if(timeObject.getAirportBox().getSelectedIndex() == 3) {

  timeObject.getMancbox().setVisible(true);
  }
  else if(timeObject.getAirportBox().getSelectedIndex() == 4) { 
 timeObject.getHeathBox().setVisible(true);
  }   

   }
  }



public static void main (String args[]) {
events mainmenu = new events(); //object is created


mainmenu.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
mainmenu.setSize(800,500);
mainmenu.setVisible(true);
mainmenu.setLayout(new BorderLayout());
mainmenu.setTitle("Learning how to use GUI");
mainmenu.setBackground(Color.BLUE);
mainmenu.setResizable(false);

}
}

我的其他課時

          import javax.swing.JOptionPane;

 import java.awt.*;
 import java.awt.event.*;
 import javax.swing.*;

 class Time
{

  private JComboBox timeAirportbox;//comboboxes declared
  private JComboBox eastMidbox;
  private JComboBox mancBox;
  private JComboBox heathBox;
  private JComboBox birmBox;
  private String[] airport = {"","EM", "Bham", "Manc", "Heath"};//array of airports   declared
  private String[] destination = {"","NY", "Cali", "FlO", "MIAMI", "Tokyo"};//array      of    destinations declared
  private JPanel timePanel;

    public void SelectTime() {



 //combobox objects created

  timePanel = new JPanel();
  timePanel.setBackground(Color.BLUE);
  timePanel.setPreferredSize(new Dimension(400, 400));

  timeAirportbox = new JComboBox(airport);//array is inserted into the JComboBox
  timePanel.add(timeAirportbox);
  timeAirportbox.setVisible(false);


  eastMidbox  = new JComboBox(destination);
  timePanel.add(eastMidbox);
  eastMidbox.setVisible(false);

  mancBox = new JComboBox(destination);
  timePanel.add(mancBox);
  mancBox.setVisible(false);

  heathBox = new JComboBox(destination);
  timePanel.add(heathBox);
  heathBox.setVisible(false);

  birmBox = new JComboBox(destination);
  timePanel.add(birmBox);
  birmBox.setVisible(false);




}



    public JPanel getTimePanel() {
    return timePanel;
    }

    public JComboBox getAirportBox() {
    return timeAirportbox;      
    }

    public JComboBox getEastMidBox() {  
    return eastMidbox;
    }       

   public JComboBox getMancbox() {
    return mancBox;
    }

  public JComboBox getHeathBox() {
    return heathBox;
    }

  public JComboBox getBirmBox()  {
    return birmBox;
    }       





    }

Answer 1

不使用在Work構造函數中構建的Time對象：

  Time timeObject = new Time();
  timeObject.SelectTime();
  buttontime2 selectDest = new buttontime2();
  timeObject.getAirportBox().addActionListener(selectDest);

由於您只將動作偵聽器selectedDest應用於未使用的timeObject的組合框，因此永遠不會調用偵聽器。

你可以做兩件事來使它工作：

• 移動創建偵聽器的代碼，並在第一個偵聽器buttontime將其分配給buttontime
• 僅創建一次Time對象並將其存儲為Work實例的成員。 由於您的偵聽器是Work類的非靜態內部類，因此它將能夠使用它而不是創建新的Time對象。

編輯：我沒有看到你的第二個聽眾，你正在建立一個新的時間對象。 這個對象實際上與您之前創建的對象不同，因此修改一個對象不會影響另一個對象。 您真的應該創建一次Time對象並將其存儲為Work類的成員變量，然后在偵聽器中使用此對象而不是重新創建它。

要清楚，這樣做：

public class Work extends JFrame {

    // ...

    private Time timeObject;

    public Work() {

        // ...

        timeObject = new Time();
        timeObject.SelectTime();
        buttontime2 selectDest = new buttontime2();
        timeObject.getAirportBox().addActionListener(selectDest);

    }

    public class buttontime implements ActionListener {
        public void actionPerformed(ActionEvent clickTime)  {
            // use timeObject, don't create it and don't call SelectTime()
            // example:
            add(timeObject.getTimePanel(),BorderLayout.EAST);
            // ....
        }
    }

    public class buttontime2 implements ActionListener {
        public void actionPerformed(ActionEvent clickTime)  {
            // use timeObject, don't create it and don't call SelectTime()

        }
    }
}

另請注意：

• 你不應該擴展JFrame，沒有理由這樣做。 重構代碼，使您的框架只是Work類的成員變量。
• 遵循Java標准代碼約定 ，尤其是使用類名稱的用例： buttonlistener應該是ButtonListener ，方法應該以小寫開頭： SelectTime應該是selectTime 。