Java自学-图形界面 事件监听

Swing 如何进行事件监听

示例 1 : 按钮监听

创建一个匿名类实现ActionListener接口，当按钮被点击时，actionPerformed方法就会被调用

package gui;
  
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
  
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
  
public class TestGUI {
    public static void main(String[] args) {
  
        JFrame f = new JFrame("LoL");
        f.setSize(400, 300);
        f.setLocation(580, 200);
        f.setLayout(null);
  
        final JLabel l = new JLabel();
  
        ImageIcon i = new ImageIcon("e:/project/j2se/shana.png");
        l.setIcon(i);
        l.setBounds(50, 50, i.getIconWidth(), i.getIconHeight());
  
        JButton b = new JButton("隐藏图片");
        b.setBounds(150, 200, 100, 30);
  
        // 给按钮 增加 监听
        b.addActionListener(new ActionListener() {
  
            // 当按钮被点击时，就会触发 ActionEvent事件
            // actionPerformed 方法就会被执行
            public void actionPerformed(ActionEvent e) {
                l.setVisible(false);
            }
        });
  
        f.add(l);
        f.add(b);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  
        f.setVisible(true);
    }
}

示例 2 : 键盘监听

键盘监听器： KeyListener
keyPressed 代表 键被按下
keyReleased 代表 键被弹起
keyTyped 代表 一个按下弹起的组合动作
KeyEvent.getKeyCode() 可以获取当前点下了哪个键

package gui;
  
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
  
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
  
public class TestGUI {
    public static void main(String[] args) {
  
        JFrame f = new JFrame("LoL");
        f.setSize(400, 300);
        f.setLocation(580, 200);
        f.setLayout(null);
  
        final JLabel l = new JLabel();
  
        ImageIcon i = new ImageIcon("e:/project/j2se/shana.png");
        l.setIcon(i);
        l.setBounds(50, 50, i.getIconWidth(), i.getIconHeight());
  
        // 增加键盘监听
        f.addKeyListener(new KeyListener() {
  
            // 键被弹起
            public void keyReleased(KeyEvent e) {
  
                // 39代表按下了 “右键”
                if (e.getKeyCode() == 39) {
                    // 图片向右移动 （y坐标不变，x坐标增加）
                    l.setLocation(l.getX() + 10, l.getY());
                }
            }
  
            //键被按下
            public void keyPressed(KeyEvent e) {
                // TODO Auto-generated method stub
  
            }
  
            // 一个按下弹起的组合动作
            public void keyTyped(KeyEvent e) {
  
            }
        });
  
        f.add(l);
  
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  
        f.setVisible(true);
    }
}

示例 3 : 鼠标监听

MouseListener 鼠标监听器
mouseReleased 鼠标释放
mousePressed 鼠标按下
mouseExited 鼠标退出
mouseEntered 鼠标进入
mouseClicked 鼠标点击
在本例中，使用mouseEntered，当鼠标进入图片的时候，图片就移动位置

package gui;
  
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.Random;
  
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
  
public class TestGUI {
    public static void main(String[] args) {
  
        final JFrame f = new JFrame("LoL");
        f.setSize(800, 600);
        f.setLocationRelativeTo(null);
        f.setLayout(null);
  
        final JLabel l = new JLabel();
        ImageIcon i = new ImageIcon("e:/project/j2se/shana_heiheihei.png");
        l.setIcon(i);
        l.setBounds(375, 275, i.getIconWidth(), i.getIconHeight());
  
        f.add(l);
  
        l.addMouseListener(new MouseListener() {
  
            // 释放鼠标
            public void mouseReleased(MouseEvent e) {
                // TODO Auto-generated method stub
  
            }
  
            // 按下鼠标
            public void mousePressed(MouseEvent e) {
                // TODO Auto-generated method stub
  
            }
  
            // 鼠标退出
            public void mouseExited(MouseEvent e) {
                // TODO Auto-generated method stub
  
            }
  
            // 鼠标进入
            public void mouseEntered(MouseEvent e) {
  
                Random r = new Random();
  
                int x = r.nextInt(f.getWidth() - l.getWidth());
                int y = r.nextInt(f.getHeight() - l.getHeight());
  
                l.setLocation(x, y);
  
            }
  
            // 按下释放组合动作为点击鼠标
            public void mouseClicked(MouseEvent e) {
                // TODO Auto-generated method stub
  
            }
        });
  
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  
        f.setVisible(true);
    }
}

示例 4 : 适配器

MouseAdapter 鼠标监听适配器
一般说来在写监听器的时候，会实现MouseListener。
但是MouseListener里面有很多方法实际上都没有用到，比如mouseReleased ，mousePressed，mouseExited等等。
这个时候就可以使用 鼠标监听适配器，MouseAdapter 只需要重写必要的方法即可。

package gui;
  
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.Random;
  
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
  
public class TestGUI {
    public static void main(String[] args) {
  
        final JFrame f = new JFrame("LoL");
        f.setSize(800, 600);
        f.setLocationRelativeTo(null);
        f.setLayout(null);
  
        final JLabel l = new JLabel("");
  
        ImageIcon i = new ImageIcon("e:/project/j2se/shana_heiheihei.png");
        l.setIcon(i);
        l.setBounds(375, 275, i.getIconWidth(), i.getIconHeight());
  
        f.add(l);
  
        // MouseAdapter 适配器，只需要重写用到的方法，没有用到的就不用写了
        l.addMouseListener(new MouseAdapter() {
  
            // 只有mouseEntered用到了
            public void mouseEntered(MouseEvent e) {
  
                Random r = new Random();
  
                int x = r.nextInt(f.getWidth() - l.getWidth());
                int y = r.nextInt(f.getHeight() - l.getHeight());
  
                l.setLocation(x, y);
  
            }
        });
  
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  
        f.setVisible(true);
    }
}

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