如何不同的ActionListener添加到相同的对象 | 如何不同的ActionListener添加到相同的对象

本文介绍了如何不同的ActionListener添加到相同的对象的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我如何不同的ActionListeners添加到P1的对象。我希望程序能够在textbar设置为适当的数量时$ P $与相应的按钮pssed。因为它们不是不同的变量，我不能简单地用code以下（在我的actionPerformed功能），

如果（e.getSource（）==按钮1）{ txtField.setText（1）; }

 进口java.awt中的*。
导入的java.applet。*;
java.awt.event中导入*。公共类电话扩展小程序实现的ActionListener
{
   文本字段txtField;   公共无效的init（）{
       的setLayout（新的BorderLayout（））;       txtField =新的TextField（）;
       加（txtField，BorderLayout.NORTH）;       面板P1 =新面板（）;
       p1.setLayout（新的GridLayout（4,3））;
       p1.add（新按钮（1））;
       p1.add（新按钮（2））;
       p1.add（新按钮（3））;
       p1.add（新按钮（4））;
       p1.add（新按钮（5））;
       p1.add（新按钮（6））;
       p1.add（新按钮（7））;
       p1.add（新按钮（8））;
       p1.add（新按钮（9））;
       p1.add（新按钮（*））;
       p1.add（新键（0））;
       p1.add（新按钮（＃））;
       加（P1，BorderLayout.CENTER）;   }   公共无效的actionPerformed（ActionEvent的五）{
    }
}

解决方案

没有你的GUI类也是监听器类作为的要求类的事太多了。相反，考虑使用匿名内部监听类或私有内部类。顺便说一句，我没有看到你添加任何听众的按钮。此外，对于我的钱，我想创建一个Swing GUI的，而不是一个AWT GUI的Swing是一个更强大和灵活的。

另外请注意，上面的例子中，我会在实际上给我所有的按钮对象相同的动作侦听器。如果使用摇摆，我可以简单地让这将是数息字符串ActionEvent对象的actionCommand。无需10 if块或交换机模块。

例如，这表明在显示一个JTextField的一些非常简单的逻辑，但没有计算逻辑：

 进口java.awt.BorderLayout中;
进口java.awt.GridLayout中;
进口java.awt.event.ActionEvent中;进口的javax.swing *。公共类CalcEg {
   私有静态最终浮动BTN_FONT_SIZE = 18F;
   私有静态最后的String [] [] = BTN_LABELS {
      {7，8，9， - }，
      {4，5，6，+}，
      {1，2，3，/}，
      {0，。，=，*}
   };
   私人的JPanel的mainPanel =新JPanel（）;
   私人JTextField的文本框=新的JTextField（10）;   公共CalcEg（）{
      诠释行= BTN_LABELS.length;
      INT COLS = BTN_LABELS [0]。长度;
      INT间隙= 4;      JPanel的buttonPanel =新JPanel（新网格布局（行，COLS，缺口，缺口））;
      对于（字符串[] btnLabelRow：BTN_LABELS）{
         对于（字符串btnLabel：btnLabelRow）{
            JButton的BTN = createButton（btnLabel）;
            如果（0123456789。含有（btnLabel））{
               btn.setAction（新NumberListener（btnLabel））;
            }
            buttonPanel.add（BTN）;
         }
      }      textField.setFont（textField.getFont（）的deriveFont（BTN_FONT_SIZE））;      mainPanel.setLayout（新的BorderLayout（间隙，间隙））;
      mainPanel.setBorder（BorderFactory.createEmptyBorder（缺口，缺口，缺口，缺口））;
      mainPanel.add（文本框，BorderLayout.PAGE_START）;
      mainPanel.add（buttonPanel，BorderLayout.CENTER）;
   }   私人的JButton createButton（字符串btnLabel）{
      JButton的按钮=的新的JButton（btnLabel）;
      button.setFont（button.getFont（）的deriveFont（BTN_FONT_SIZE））;
      返回按钮;
   }   公共JComponent的getMainComponent（）{
      返回mainPanel中;
   }   私有类NumberListener扩展AbstractAction {
      NumberListener（字符串actionCommand）{
         超（actionCommand）;
      }      @覆盖
      公共无效的actionPerformed（ActionEvent的五）{
         串actionCommand = e.getActionCommand（）;
         textField.setText（textField.getText（）+ actionCommand）;
      }
   }   私有静态无效createAndShowGui（）{
      CalcEg的mainPanel =新CalcEg（）;      JFrame的帧=新的JFrame（CalcEg）;
      frame.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）;
      。frame.getContentPane（）加（mainPanel.getMainComponent（））;
      frame.pack（）;
      frame.setLocationByPlatform（真）;
      frame.setVisible（真）;
   }   公共静态无效的主要（字串[] args）{
      SwingUtilities.invokeLater（Runnable的新（）{
         公共无效的run（）{
            createAndShowGui（）;
         }
      }）;
   }
}

How do I add different actionlisteners to the p1 objects. I want the program to be able to set the textbar to the appropriate number when pressed with the appropriate button. Since they are not different variables I cannot simply use the code below(in my actionPerformed function),

if (e.getSource() == button1){ txtField.setText("1"); }

import java.awt.*;
import java.applet.*;
import java.awt.event.*;

public class Telephone extends Applet implements ActionListener
{
   TextField txtField;

   public void init() {
       setLayout(new BorderLayout());

       txtField = new TextField("");
       add(txtField, BorderLayout.NORTH);

       Panel p1 = new Panel();
       p1.setLayout(new GridLayout(4, 3));
       p1.add(new Button("1"));
       p1.add(new Button("2"));
       p1.add(new Button("3"));
       p1.add(new Button("4"));
       p1.add(new Button("5"));
       p1.add(new Button("6"));
       p1.add(new Button("7"));
       p1.add(new Button("8"));
       p1.add(new Button("9"));
       p1.add(new Button("*"));
       p1.add(new Button("0"));
       p1.add(new Button("#"));
       add(p1, BorderLayout.CENTER);

   }

   public void actionPerformed(ActionEvent e) {


    }
}

解决方案

Don't have your GUI class also be your listener class as that's asking the class to do too much. Instead consider using anonymous inner listener classes or private inner classes. Incidentally, I don't see where you're adding any listeners to your buttons. Also, for my money, I'd create a Swing GUI, not an AWT GUI as Swing is much more robust and flexible.

Also note, for the example above, I would in fact give all my button objects the same action listener. If using Swing, I could simply get the ActionEvent object's actionCommand which would be the number String of interest. No need for 10 if blocks or a switch block.

For example, this demonstrates very simple logic of displaying the number in a JTextField, but has no calculation logic:

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;

import javax.swing.*;

public class CalcEg {
   private static final float BTN_FONT_SIZE = 18f;
   private static final String[][] BTN_LABELS = {
      {"7", "8", "9", "-"},
      {"4", "5", "6", "+"},
      {"1", "2", "3", "/"},
      {"0", ".", "=", "*"}
   };
   private JPanel mainPanel = new JPanel();
   private JTextField textField = new JTextField(10);

   public CalcEg() {
      int rows = BTN_LABELS.length;
      int cols = BTN_LABELS[0].length;
      int gap = 4;

      JPanel buttonPanel = new JPanel(new GridLayout(rows, cols, gap, gap));
      for (String[] btnLabelRow : BTN_LABELS) {
         for (String btnLabel : btnLabelRow) {
            JButton btn = createButton(btnLabel);
            if ("0123456789.".contains(btnLabel)) {
               btn.setAction(new NumberListener(btnLabel));
            }
            buttonPanel.add(btn);
         }
      }

      textField.setFont(textField.getFont().deriveFont(BTN_FONT_SIZE));

      mainPanel.setLayout(new BorderLayout(gap, gap));
      mainPanel.setBorder(BorderFactory.createEmptyBorder(gap, gap, gap, gap));
      mainPanel.add(textField, BorderLayout.PAGE_START);
      mainPanel.add(buttonPanel, BorderLayout.CENTER);
   }

   private JButton createButton(String btnLabel) {
      JButton button = new JButton(btnLabel);
      button.setFont(button.getFont().deriveFont(BTN_FONT_SIZE));
      return button;
   }

   public JComponent getMainComponent() {
      return mainPanel;
   }

   private class NumberListener extends AbstractAction {
      NumberListener(String actionCommand) {
         super(actionCommand);
      }

      @Override
      public void actionPerformed(ActionEvent e) {
         String actionCommand = e.getActionCommand();
         textField.setText(textField.getText() + actionCommand);
      }
   }

   private static void createAndShowGui() {
      CalcEg mainPanel = new CalcEg();

      JFrame frame = new JFrame("CalcEg");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel.getMainComponent());
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

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