事件监听器

《零基础学Java》

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• 事件监听器

  为按钮等添加事件监听器，事件监听器的作用是在用户单击按钮时，设置窗体要实现的功能。

• 动作事件监听器

动作事件监听器(AbstractAction)监听器是Swing中比较常用的事件监听器，很多最近的动作都会使用它监听（比如：按钮被单击）。

动作事件监听器

动作事件监听器 实例

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
 
public class Demo17 extends JFrame {
    public Demo17(){
        setBounds(100,100,300,200);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
 
        Container c = getContentPane();
        c.setLayout(new FlowLayout());
 
        JLabel jLabel = new JLabel("标签");
        c.add(jLabel);
 
        /**
         * 为 按钮 添加动作监听
         */
        JButton jButton = new JButton("按钮");
        jButton.addActionListener(new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jLabel.setText("按钮被点击");
            }
        });
        c.add(jButton);
 
        /**
         * 为 文本框 添加动作监听
         */
        JTextField jTextField = new JTextField(10);
        c.add(jTextField);
        jTextField.addActionListener(new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                Object obj = e.getSource();//捕捉这个动作由那个按键触发的
                JTextField jTextField1 = (JTextField)obj;
                System.out.println(jTextField1.getText());
 
                jLabel.setText("文本框中点击了回车");
            }
        });
 
        /**
         * 为 多选框 添加动作监听
         */
        JCheckBox jCheckBox = new JCheckBox("多选框");
        c.add(jCheckBox);
        jCheckBox.addActionListener(new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jLabel.setText("多选框被点击");
            }
        });
 
        /**
         * 为 单选框 添加动作监听
         */
        JRadioButton jRadioButton = new JRadioButton("单选框");
        c.add(jRadioButton);
        jRadioButton.addActionListener(new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jLabel.setText("单选框被点击");
            }
        });
 
        /**
         * 为 下拉列表 添加动作监听
         */
        String string[] = {"选项1","选项2"};
        JComboBox jComboBox = new JComboBox(string);
        c.add(jComboBox);
        jComboBox.addActionListener(new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jLabel.setText("下拉列表被选择");
            }
        });
 
        setVisible(true);
    }
 
    public static void main(String[] args) {
        new Demo17();
    }
}

动作事件监听器 实例输出结果：

• 键盘事件

  当向文本框中输入文本内容时，将触发键盘事件。KeyEvent类 负责捕获键盘事件，可以通过为组
  件添加实现了 KeyListener接口 的监听器类，来处理该组件触发的键盘事件。

  KeyListener接口的三个方法：

  keyListener.addKeyListener(new KeyListener() {
              @Override
              public void keyTyped(KeyEvent e) {
  			//发生击键事件时触发
              }
   
              @Override
              public void keyPressed(KeyEvent e) {
  			//按键被按下时触发
              }
   
              @Override
              public void keyReleased(KeyEvent e) {
              //按键被释放时触发
              }
          });

  KeyListener类的常用方法：

(PS：在 KeyEvent类 中以 “VK_” 开头的静态常量代表各个按键的 keyCode，可以通过这些
静态常量判断事件中的按键，获得按键的标签。)

键盘事件 实例：

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
 
public class LoginAuthentication extends JFrame {
 
    private JPanel jPanel1;
    private JPanel jPanel2;
    private JTextField account;
    private JPasswordField password;
    private JButton jButton;
    private String zh = "123";
    private String mm = "456";
 
    public LoginAuthentication() {
        setBounds(100, 100, 320, 230);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setTitle("目前状态：正在登录中");
 
        Container c = getContentPane();
        c.setLayout(new FlowLayout());
 
        jPanel1 = new JPanel(new FlowLayout());
        jPanel1.setBorder(BorderFactory.createTitledBorder("账号"));
        account = new JTextField(20);
        account.addKeyListener(new KeyListener() {//创建键盘事件
            @Override
            public void keyTyped(KeyEvent e) {
 
            }
 
            @Override
            public void keyPressed(KeyEvent e) {
 
            }
 
            @Override
            public void keyReleased(KeyEvent e) {
                int dl = e.getKeyCode();
                switch (dl) {
                    case KeyEvent.VK_ENTER:
                        password.requestFocus();
                        return;
                }
            }
        });
        jPanel1.add(account);
        c.add(jPanel1);
 
        jPanel2 = new JPanel(new FlowLayout());
        jPanel2.setBorder(BorderFactory.createTitledBorder("密码"));
        password = new JPasswordField(20);
        jPanel2.add(password);
        c.add(jPanel2);
 
        jButton = new JButton("登录");
        jButton.addActionListener(new AbstractAction() {//创建鼠标事件
            @Override
            public void actionPerformed(ActionEvent e) {
                if (account.getText().equals(zh)) {
                    char ch[] = password.getPassword();
                    String zhu = new String(ch);
                    if (zhu.equals(mm)) {
                        System.out.println("登录成功");
                        setTitle("目前状态：登录成功");
                    }else{
                        System.out.println("登录失败");
                        setTitle("目前状态：登录失败");
                    }
                }else {
                    System.out.println("登录失败");
                    setTitle("目前状态：登录失败");
                }
            }
        });
        c.add(jButton);
 
        setVisible(true);
    }
 
    public static void main(String[] args) {
        new LoginAuthentication();
    }
}

键盘事件 实例输出结果：

• 鼠标事件

  所有组件都能应用鼠标事件， MouseEvent类 负责捕获鼠标事件，可以通过为组件添加实现了
  MouseListener接口的监听器类来处理该组件触发的鼠标事件。MouseListener接口 共有5个抽象方法，分别在光标移入、光标移出、鼠标按键被按下、鼠标按键被释放、鼠标按键被单击 事件时被触发。

  MouseListener接口的五个方法：

 clickArea.addMouseListener(new MouseListener() {
            @Override
            public void mouseClicked(MouseEvent e) {
                //鼠标点击
            }
 
            @Override
            public void mousePressed(MouseEvent e) {
				//按键按下
            }
 
            @Override
            public void mouseReleased(MouseEvent e) {
				//按键释放
            }
 
            @Override
            public void mouseEntered(MouseEvent e) {
                //鼠标进入
            }
 
            @Override
            public void mouseExited(MouseEvent e) {
         		//鼠标退出
            }
        });

MouseEvent类的常用方法：

MouseEvent类中代表鼠标按键的静态常量：

鼠标事件 实例：

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
 
public class Demo19 extends JFrame {
    private JScrollPane jScrollPane;
    private JTextArea out;
    private JPanel promptArea;
    private JPanel clickArea;
 
    public Demo19(){
        setBounds(100,100,450,400);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setTitle("鼠标事件");
 
        Container c =getContentPane();
        c.setLayout(new GridLayout(1,2));
 
        promptArea=new JPanel(new FlowLayout());
        promptArea.setBorder(BorderFactory.createTitledBorder("输出区域"));
        out=new JTextArea("",18,18);
        jScrollPane=new JScrollPane(out);
        promptArea.add(jScrollPane);
        c.add(promptArea);
 
        clickArea=new JPanel(new FlowLayout());
        clickArea.setBorder(BorderFactory.createTitledBorder("点击区域"));
        clickArea.addMouseListener(new MouseListener() {
            @Override
            public void mouseClicked(MouseEvent e) {//鼠标点击
                int hitCount = e.getClickCount();//鼠标点击次数
                int clickButton = e.getButton();//鼠标点击的按键
                switch (clickButton){
                    case MouseEvent.BUTTON1:
                        out.append("鼠标左键点击了"+hitCount+"次组件\n");
                        break;
                    case MouseEvent.BUTTON2:
                        out.append("鼠标中键点击了"+hitCount+"次组件\n");
                        break;
                    case MouseEvent.BUTTON3:
                        out.append("鼠标右键点击了"+hitCount+"次组件\n");
                        break;
                }
            }
 
            @Override
            public void mousePressed(MouseEvent e) {//按键按下
 
            }
 
            @Override
            public void mouseReleased(MouseEvent e) {//按键释放
 
            }
 
            @Override
            public void mouseEntered(MouseEvent e) {//鼠标进入
                out.append("鼠标进入组件\n");
            }
 
            @Override
            public void mouseExited(MouseEvent e) {//鼠标退出
                out.append("鼠标退出组件\n");
            }
        });
        c.add(clickArea);
 
 
 
 
        setVisible(true);
    }
 
    public static void main(String[] args) {
        new Demo19();
    }
}

鼠标事件 实例输出结果：

• 窗体事件

  WindowListener接口中五个方法：

  public DemoWindw(){
          addWindowListener(new MywindowListener());//创建窗体事件监听
      }
   
  class MywindowListener implements WindowListener{
   
          @Override
          public void windowOpened(WindowEvent e) { 
            	//窗体打开
          }
   
          @Override
          public void windowClosing(WindowEvent e) {
              //窗体将要关闭
          }
   
          @Override
          public void windowClosed(WindowEvent e) {
              //窗体已经关闭
          }
   
          @Override
          public void windowIconified(WindowEvent e) {
              //窗体最小化
          }
   
          @Override
          public void windowDeiconified(WindowEvent e) {
              //窗体恢复正常大小
          }
   
          @Override
          public void windowActivated(WindowEvent e) {
              //窗体激活
          }
   
          @Override
          public void windowDeactivated(WindowEvent e) {
              //窗体失去激活
          }
      }

  窗体事件 实例：

  import javax.swing.*;
  import java.awt.event.WindowEvent;
  import java.awt.event.WindowListener;
   
  public class Demo20 extends JFrame {
      public Demo20(){
          setBounds(100,100,300,300);
          /**
           * EXIT_ON_CLOSE：关闭窗口同时停止程序
           * DISPOSE_ON_CLOSE：关闭窗口时释放窗体资源
           */
          setDefaultCloseOperation(DISPOSE_ON_CLOSE);
          setVisible(true);
   
          addWindowListener(new MywindowListener());//创建窗体事件监听
      }
   
      class MywindowListener implements WindowListener{
   
          @Override
          public void windowOpened(WindowEvent e) { //窗体打开
              System.out.println("窗体被打开");
          }
   
          @Override
          public void windowClosing(WindowEvent e) {//窗体将要关闭
              System.out.println("窗体将要被关闭");
          }
   
          @Override
          public void windowClosed(WindowEvent e) {//窗体已经关闭
              /**
               * 如果使用EXIT_ON_CLOSE(关闭窗口同时停止程序)可能无法触发此方法
               */
              System.out.println("窗体已经被关闭");
          }
   
          @Override
          public void windowIconified(WindowEvent e) {//窗体最小化
              System.out.println("窗体最小化");
          }
   
          @Override
          public void windowDeiconified(WindowEvent e) {//窗体恢复正常大小
              System.out.println("窗体恢复正常大小");
          }
   
          @Override
          public void windowActivated(WindowEvent e) {//窗体激活
              System.out.println("窗体被激活");
          }
   
          @Override
          public void windowDeactivated(WindowEvent e) {//窗体失去激活
              System.out.println("窗体失去激活");
          }
      }
   
      public static void main(String[] args) {
          new Demo20();
      }
  }

  窗体事件 实例输出结果：