Java程序设计 图形用户界面 【七】事件处理上
事件和监听器
事件：表示一个对象发生状态变化
监听器：不断地监听事件的变化，并根据这些事件进行相应地处理
事件类 EventObject类
EventObject类的定义格式
public class EventObject extends Object implements Serializable{
public EventObject(Object source){
// 构造一个发生事件的对象
}
public Object getSource(){
// 返回一个事件对象
}
public String toString(){
// 得到信息
}
}
Java事件处理流程
WindowListener是专门处理窗体事件的监听接口
| 方法 | 作用 |
|---|---|
| void windowActivated(WindowEvent e) | 将窗口变为活动窗口时触发 |
| void windowDeactivated(WindowEvent e) | 将窗口变为不活动窗口时触发 |
| void windowClosed(WindowEvent e) | 当窗口被关闭时触发 |
| void windowClosing(WindowEvent e) | 当窗口正在关闭时触发 |
| void windowIconified(WindowEvent e) | 窗口最小化时触发 |
| void windowDeiconified(WindowEvent e) | 窗口从最小化恢复到正常状态时触发 |
| void windowOpened(WindowEvent e) | 窗口打开时触发 |
实现WindowListener
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
public class WindowEventHandle implements WindowListener {
@Override
public void windowActivated(WindowEvent e) {
System.out.println("窗口被选中");
}
@Override
public void windowClosed(WindowEvent e) {
System.out.println("窗口被关闭");
}
@Override
public void windowClosing(WindowEvent e) {
System.out.println("窗口关闭");
}
@Override
public void windowDeactivated(WindowEvent e) {
System.out.println("取消窗口选中");
}
@Override
public void windowDeiconified(WindowEvent e) {
System.out.println("窗口从最小化恢复");
}
@Override
public void windowIconified(WindowEvent e) {
System.out.println("窗口最小化");
}
@Override
public void windowOpened(WindowEvent e) {
System.out.println("窗口被打开");
}
}
在窗体上注册事件监听器
import javax.swing.*;
import java.awt.*;
public class Hello {
public static void main(String[] args) {
JFrame frame = new JFrame("一");
frame.addWindowListener(new WindowEventHandle());
frame.setSize(500,300);
frame.setBackground(Color.BLUE);
frame.setLocation(500,500);
frame.setVisible(true);
}
}
方便用户进行事件处理的实现。以WindowAdapter为例，用户只要继承了此类，就可以根据自己的需要覆写方法，如果现在只关心窗口关闭方法，则只在子类中覆写windowClosing()方法即可
通过WindowAdapter实现监听
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
public class WindowEventHandle extends WindowAdapter {
@Override
public void windowClosing(WindowEvent e) {
super.windowClosing(e);
System.out.println("窗口关闭");
System.exit(1);
}
}
而在窗体操作的代码中，直接使用以上的监听器类即可
import javax.swing.*;
import java.awt.*;
public class Hello {
public static void main(String[] args) {
JFrame frame = new JFrame("一");
frame.addWindowListener(new WindowEventHandle());
frame.setSize(500,300);
frame.setBackground(Color.BLUE);
frame.setLocation(500,500);
frame.setVisible(true);
}
}
使用匿名内部类
import javax.swing.*;
import java.awt.*;
import java.awt.event.WindowEvent;
public class Hello {
public static void main(String[] args) {
JFrame frame = new JFrame("一");
frame.addWindowListener(new WindowEventHandle(){
@Override
public void windowClosing(WindowEvent e) {
super.windowClosing(e);
System.exit(1);
}
});
frame.setSize(500,300);
frame.setBackground(Color.BLUE);
frame.setLocation(500,500);
frame.setVisible(true);
}
}
如果现在使用适配器操作类，则直接编写匿名内部类就可以减少监听类的定义
