增加和減少gui不增加不確定是否會出錯

Question

幫助試圖做出增加和減少按鈕，增加和減少面板上的數字只是對我沒有工作試圖讓actionPerformed和行動監聽器沒有工作可以有人給我的指導`

public class IncrDecPanel extends JPanel 
{ 




private int INITIAL_NUMBER = 50; 
private JButton Incr, Dec; 
private JLabel label; 
private JPanel ButtonPanel; 
private int number; 

public IncrDecPanel() 
{ 


    number = INITIAL_NUMBER; 

    label = new JLabel(String.valueOf(number)); 

    Incr = new JButton("Incr"); 
    Dec = new JButton("Dec"); 


    JButton IncrButton = new JButton("Increment"); 
    IncrButton.addActionListener (new IncrListener()); 


    JButton DecButton = new JButton("Decrement"); 
    DecButton.addActionListener(new DecListener()); 



     ButtonPanel = new JPanel(); 
     ButtonPanel.setPreferredSize(new Dimension(200, 40)); 
     ButtonPanel.setBackground(Color.red); 
     ButtonPanel.add(Incr); 
     ButtonPanel.add(Dec); 

     12 
     setPreferredSize(new Dimension(200, 80)); 
     setBackground(Color.black); 
     add(label); 
     add(ButtonPanel); 
} 


private class IncrListener implements ActionListener 
    { 

     public void actionPerformed (ActionEvent event) 
     { 
     label.setText (Integer.toString (++number)); 
     } 
    } 
     private class DecListener implements ActionListener 
     { 

      public void actionPerformed (ActionEvent event) 
      { 
       label.setText (Integer.toString (--number)); 
      } 

     } 
}` 

Answer 1

您正在將ActionListeners添加到錯誤的按鈕。 您已創建按鈕Incr和Dec，然後在將Incr和Dec添加到JPanel之前，將您的收聽者添加到IncrButton和DecButton。只需在創建後將聽衆分配給第一個按鈕，如：

Incr = new JButton("Incr"); 
    Dec = new JButton("Dec"); 

    Incr.addActionListener(new IncrListener()); 
    Dec.addActionListener(new DecListener()); 

希望這有助於您。 :)