java - 按钮的 ActionListener

Question

因此，我为我的一个类开发了一个程序，以便在单击按钮时使用 ActionListener 处理事件。我的程序可以正常工作，但是当单击任何按钮时，您必须多次单击输入按钮才能注册答案并移至程序的下一级。

示例 1:警报按钮打开 2 有时 3 “嘿，你身上有问题!”消息对话框。

示例 2:是/否提示您 3-4 次将您的是/否答案返回到 txt。

示例 3:在将输入返回到 txt 之前，颜色需要 3/4 次点击。

(我想你明白了……)

我这辈子都搞不懂为什么它不接受一个输入然后继续...

我的程序代码供您审阅...在此先感谢您。

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


public class MessageBoxes{

  private JButton alert = new JButton("Alert");
  private JButton yesNo = new JButton("Yes/No");
  private JButton color = new JButton("Color");
  private JButton vals = new JButton("3 Vals");
  private JButton input = new JButton("Input");

  private JTextField txt = new JTextField(15);

  private JFrame frame;

  private ActionListener al = new ActionListener(){
    public void actionPerformed(ActionEvent e){

    alert.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e)
        {
            //Execute when button is pressed
            JOptionPane.showMessageDialog(null,
                                  "There's a bug on you!", "Hey!",
                                  JOptionPane.ERROR_MESSAGE);
        }
    });  

    yesNo.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e)
        {
            //Execute when button is pressed
            int val = JOptionPane.showConfirmDialog(null,
                                  "Choose yes or no", "Your Call...",
                                  JOptionPane.YES_NO_OPTION);

            if(val != JOptionPane.CLOSED_OPTION){
              if(val == 0){
                txt.setText("Yes");
            }
            else{
                txt.setText("No");
            }
            }
        }
    });  

    color.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e)
        {
            //Execute when button is pressed
            Object[] options = {"Red", "Green"};

            int sel = JOptionPane.showOptionDialog(null,
                            "Choose a Color!", "Warning",
                            JOptionPane.DEFAULT_OPTION,
                            JOptionPane.WARNING_MESSAGE, null,
                                        options, options[0]);

            if(sel != JOptionPane.CLOSED_OPTION){
                txt.setText("Color Selected: " + options[sel]);
            }
        }
    });  

    vals.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e)
        {
            //Execute when button is pressed
            Object[] selections = {"First", "Second", "Third"};

            Object val = JOptionPane.showInputDialog(null,
                                             "Choose one", "Input",
                                             JOptionPane.INFORMATION_MESSAGE,
                                             null, selections, selections[0]);

            if(val != null){
                txt.setText(val.toString());
            }
        }
    });

    input.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e)
        {
            //Execute when button is pressed
            String val = JOptionPane.showInputDialog("How mant fingers do you see?");

                txt.setText(val);
        }
    });  
  }
  };



  public MessageBoxes(){

    frame = new JFrame("Title");

    frame.setSize(250, 250);

    frame.getContentPane().setLayout(new FlowLayout());

    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    frame.getContentPane().add(alert);
    frame.getContentPane().add(yesNo);
    frame.getContentPane().add(color);
    frame.getContentPane().add(vals);
    frame.getContentPane().add(input);
    frame.getContentPane().add(txt);

    frame.setVisible(true);

  }

  public void launchJFrame(){

    alert.addActionListener(al);
    yesNo.addActionListener(al);
    color.addActionListener(al);
    vals.addActionListener(al);
    input.addActionListener(al);

}

 public static void main(String [] args){

    MessageBoxes messageBoxes = new MessageBoxes();
    messageBoxes.launchJFrame();
 }
}

Answer 1

问题是，每次在 ActionListener al 中调用 actionPerformed 时，它都会注册新的 ActionListener s 用你的按钮

private ActionListener al = new ActionListener() {
    public void actionPerformed(ActionEvent e) {

        alert.addActionListener(new ActionListener() {
            //...
        });

        yesNo.addActionListener(new ActionListener() {
            //...
        });

        color.addActionListener(new ActionListener() {
            //...
        });

        vals.addActionListener(new ActionListener() {
            //...
        });

        input.addActionListener(new ActionListener() {
            //...
        });
    }
};

因此，每次调用 actionPerformed 方法时，每个按钮都会注册一个新的 actionListener。

相反，您可以使用 if-else 语句来确定事件的来源，例如...

Object source = e.getSource();
if (source == alert) {
    JOptionPane.showMessageDialog(null,
                    "There's a bug on you!", "Hey!",
                    JOptionPane.ERROR_MESSAGE);
} else if (...

或者您可以完全摆脱 ActionListener al 并简单地将各个 ActionListener 注册到 launchJFrame 中的按钮 方法...

public void launchJFrame() {

    alert.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            //Execute when button is pressed
        }
    });

    yesNo.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            //Execute when button is pressed
            int val = JOptionPane.showConfirmDialog(null,
                            "Choose yes or no", "Your Call...",
                            JOptionPane.YES_NO_OPTION);

            if (val != JOptionPane.CLOSED_OPTION) {
                if (val == 0) {
                    txt.setText("Yes");
                } else {
                    txt.setText("No");
                }
            }
        }
    });

    color.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            //Execute when button is pressed
            Object[] options = {"Red", "Green"};

            int sel = JOptionPane.showOptionDialog(null,
                            "Choose a Color!", "Warning",
                            JOptionPane.DEFAULT_OPTION,
                            JOptionPane.WARNING_MESSAGE, null,
                            options, options[0]);

            if (sel != JOptionPane.CLOSED_OPTION) {
                txt.setText("Color Selected: " + options[sel]);
            }
        }
    });

    vals.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            //Execute when button is pressed
            Object[] selections = {"First", "Second", "Third"};

            Object val = JOptionPane.showInputDialog(null,
                            "Choose one", "Input",
                            JOptionPane.INFORMATION_MESSAGE,
                            null, selections, selections[0]);

            if (val != null) {
                txt.setText(val.toString());
            }
        }
    });

    input.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            //Execute when button is pressed
            String val = JOptionPane.showInputDialog("How mant fingers do you see?");

            txt.setText(val);
        }
    });

}