事件監聽器

《零基礎學Java》

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• 事件監聽器

  為按鈕等添加事件監聽器，事件監聽器的作用是在用戶單擊按鈕時，設置窗體要實現的功能。

• 動作事件監聽器

動作事件監聽器(AbstractAction)監聽器是Swing中比較常用的事件監聽器，很多最近的動作都會使用它監聽（比如：按鈕被單擊）。

動作事件監聽器

動作事件監聽器 實例

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("標簽");
        c.add(jLabel);

        /**
         * 為 按鈕 添加動作監聽
         */
        JButton jButton = new JButton("按鈕");
        jButton.addActionListener(new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jLabel.setText("按鈕被點擊");
            }
        });
        c.add(jButton);

        /**
         * 為 文本框 添加動作監聽
         */
        JTextField jTextField = new JTextField(10);
        c.add(jTextField);
        jTextField.addActionListener(new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                Object obj = e.getSource();//捕捉這個動作由那個按鍵觸發的
                JTextField jTextField1 = (JTextField)obj;
                System.out.println(jTextField1.getText());

                jLabel.setText("文本框中點擊了回車");
            }
        });

        /**
         * 為 多選框 添加動作監聽
         */
        JCheckBox jCheckBox = new JCheckBox("多選框");
        c.add(jCheckBox);
        jCheckBox.addActionListener(new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jLabel.setText("多選框被點擊");
            }
        });

        /**
         * 為 單選框 添加動作監聽
         */
        JRadioButton jRadioButton = new JRadioButton("單選框");
        c.add(jRadioButton);
        jRadioButton.addActionListener(new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jLabel.setText("單選框被點擊");
            }
        });

        /**
         * 為 下拉列表 添加動作監聽
         */
        String string[] = {"選項1","選項2"};
        JComboBox jComboBox = new JComboBox(string);
        c.add(jComboBox);
        jComboBox.addActionListener(new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jLabel.setText("下拉列表被選擇");
            }
        });

        setVisible(true);
    }

    public static void main(String[] args) {
        new Demo17();
    }
}

動作事件監聽器 實例輸出結果：

• 鍵盤事件

  當向文本框中輸入文本內容時，將觸發鍵盤事件。KeyEvent類 負責捕獲鍵盤事件，可以通過為組
  件添加實現了 KeyListener接口 的監聽器類，來處理該組件觸發的鍵盤事件。

  KeyListener接口的三個方法：

  keyListener.addKeyListener(new KeyListener() {
              @Override
              public void keyTyped(KeyEvent e) {
  			//發生擊鍵事件時觸發
              }
  
              @Override
              public void keyPressed(KeyEvent e) {
  			//按鍵被按下時觸發
              }
  
              @Override
              public void keyReleased(KeyEvent e) {
              //按鍵被釋放時觸發
              }
          });
  

  KeyListener類的常用方法：

(PS：在 KeyEvent類 中以 “VK_” 開頭的靜態常量代表各個按鍵的 keyCode，可以通過這些
靜態常量判斷事件中的按鍵，獲得按鍵的標簽。)

鍵盤事件 實例：

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("目前狀態：正在登錄中");

        Container c = getContentPane();
        c.setLayout(new FlowLayout());

        jPanel1 = new JPanel(new FlowLayout());
        jPanel1.setBorder(BorderFactory.createTitledBorder("賬號"));
        account = new JTextField(20);
        account.addKeyListener(new KeyListener() {//創建鍵盤事件
            @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("密碼"));
        password = new JPasswordField(20);
        jPanel2.add(password);
        c.add(jPanel2);

        jButton = new JButton("登錄");
        jButton.addActionListener(new AbstractAction() {//創建鼠標事件
            @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("登錄成功");
                        setTitle("目前狀態：登錄成功");
                    }else{
                        System.out.println("登錄失敗");
                        setTitle("目前狀態：登錄失敗");
                    }
                }else {
                    System.out.println("登錄失敗");
                    setTitle("目前狀態：登錄失敗");
                }
            }
        });
        c.add(jButton);

        setVisible(true);
    }

    public static void main(String[] args) {
        new LoginAuthentication();
    }
}

鍵盤事件 實例輸出結果：

• 鼠標事件

  所有組件都能應用鼠標事件， MouseEvent類 負責捕獲鼠標事件，可以通過為組件添加實現了
  MouseListener接口的監聽器類來處理該組件觸發的鼠標事件。MouseListener接口 共有5個抽象方法，分別在光標移入、光標移出、鼠標按鍵被按下、鼠標按鍵被釋放、鼠標按鍵被單擊 事件時被觸發。

  MouseListener接口的五個方法：

 clickArea.addMouseListener(new MouseListener() {
            @Override
            public void mouseClicked(MouseEvent e) {
                //鼠標點擊
            }

            @Override
            public void mousePressed(MouseEvent e) {
				//按鍵按下
            }

            @Override
            public void mouseReleased(MouseEvent e) {
				//按鍵釋放
            }

            @Override
            public void mouseEntered(MouseEvent e) {
                //鼠標進入
            }

            @Override
            public void mouseExited(MouseEvent e) {
         		//鼠標退出
            }
        });

MouseEvent類的常用方法：

MouseEvent類中代表鼠標按鍵的靜態常量：

鼠標事件 實例：

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("鼠標事件");

        Container c =getContentPane();
        c.setLayout(new GridLayout(1,2));

        promptArea=new JPanel(new FlowLayout());
        promptArea.setBorder(BorderFactory.createTitledBorder("輸出區域"));
        out=new JTextArea("",18,18);
        jScrollPane=new JScrollPane(out);
        promptArea.add(jScrollPane);
        c.add(promptArea);

        clickArea=new JPanel(new FlowLayout());
        clickArea.setBorder(BorderFactory.createTitledBorder("點擊區域"));
        clickArea.addMouseListener(new MouseListener() {
            @Override
            public void mouseClicked(MouseEvent e) {//鼠標點擊
                int hitCount = e.getClickCount();//鼠標點擊次數
                int clickButton = e.getButton();//鼠標點擊的按鍵
                switch (clickButton){
                    case MouseEvent.BUTTON1:
                        out.append("鼠標左鍵點擊了"+hitCount+"次組件\n");
                        break;
                    case MouseEvent.BUTTON2:
                        out.append("鼠標中鍵點擊了"+hitCount+"次組件\n");
                        break;
                    case MouseEvent.BUTTON3:
                        out.append("鼠標右鍵點擊了"+hitCount+"次組件\n");
                        break;
                }
            }

            @Override
            public void mousePressed(MouseEvent e) {//按鍵按下

            }

            @Override
            public void mouseReleased(MouseEvent e) {//按鍵釋放

            }

            @Override
            public void mouseEntered(MouseEvent e) {//鼠標進入
                out.append("鼠標進入組件\n");
            }

            @Override
            public void mouseExited(MouseEvent e) {//鼠標退出
                out.append("鼠標退出組件\n");
            }
        });
        c.add(clickArea);




        setVisible(true);
    }

    public static void main(String[] args) {
        new Demo19();
    }
}

鼠標事件 實例輸出結果：

• 窗體事件

  WindowListener接口中五個方法：

  public DemoWindw(){
          addWindowListener(new MywindowListener());//創建窗體事件監聽
      }
  
  class MywindowListener implements WindowListener{
  
          @Override
          public void windowOpened(WindowEvent e) { 
            	//窗體打開
          }
  
          @Override
          public void windowClosing(WindowEvent e) {
              //窗體將要關閉
          }
  
          @Override
          public void windowClosed(WindowEvent e) {
              //窗體已經關閉
          }
  
          @Override
          public void windowIconified(WindowEvent e) {
              //窗體最小化
          }
  
          @Override
          public void windowDeiconified(WindowEvent e) {
              //窗體恢復正常大小
          }
  
          @Override
          public void windowActivated(WindowEvent e) {
              //窗體激活
          }
  
          @Override
          public void windowDeactivated(WindowEvent e) {
              //窗體失去激活
          }
      }
  

  窗體事件 實例：

  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：關閉窗口同時停止程序
           * DISPOSE_ON_CLOSE：關閉窗口時釋放窗體資源
           */
          setDefaultCloseOperation(DISPOSE_ON_CLOSE);
          setVisible(true);
  
          addWindowListener(new MywindowListener());//創建窗體事件監聽
      }
  
      class MywindowListener implements WindowListener{
  
          @Override
          public void windowOpened(WindowEvent e) { //窗體打開
              System.out.println("窗體被打開");
          }
  
          @Override
          public void windowClosing(WindowEvent e) {//窗體將要關閉
              System.out.println("窗體將要被關閉");
          }
  
          @Override
          public void windowClosed(WindowEvent e) {//窗體已經關閉
              /**
               * 如果使用EXIT_ON_CLOSE(關閉窗口同時停止程序)可能無法觸發此方法
               */
              System.out.println("窗體已經被關閉");
          }
  
          @Override
          public void windowIconified(WindowEvent e) {//窗體最小化
              System.out.println("窗體最小化");
          }
  
          @Override
          public void windowDeiconified(WindowEvent e) {//窗體恢復正常大小
              System.out.println("窗體恢復正常大小");
          }
  
          @Override
          public void windowActivated(WindowEvent e) {//窗體激活
              System.out.println("窗體被激活");
          }
  
          @Override
          public void windowDeactivated(WindowEvent e) {//窗體失去激活
              System.out.println("窗體失去激活");
          }
      }
  
      public static void main(String[] args) {
          new Demo20();
      }
  }
  

  窗體事件 實例輸出結果：