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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