java事件处理机制

Java事件处理机制是一种基于委派事件模型的机制。当事件发生时，产生事件的对象会将事件的信息传递给事件的监听者进行处理。事件的信息实际上是由java.awt.event事件类库中的某个类创建的对象。

以下是几种Java事件处理的方式：
1. 使用Action和ActionListener机制：

import java.awt.*;
import java.awt.event.*;

public class MyButton extends Frame {
    private Button button;

    public MyButton() {
        button = new Button("Click me");
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                System.out.println("Button clicked");
            }
        });
        add(button);
        setSize(300, 200);
        setVisible(true);
    }

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

2. 使用普通方法调用：

import java.awt.*;
import java.awt.event.*;

public class MyButton extends Frame {
    private Button button;

    public MyButton() {
        button = new Button("Click me");
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                buttonClicked();
            }
        });
        add(button);
        setSize(300, 200);
        setVisible(true);
    }

    public void buttonClicked() {
        System.out.println("Button clicked");
    }

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

3. 使用回调函数：

import java.awt.*;
import java.awt.event.*;

public class MyButton extends Frame {
    private Button button;

    public MyButton() {
        button = new Button("Click me");
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                buttonClicked(new ButtonEvent());
            }
        });
        add(button);
        setSize(300, 200);
        setVisible(true);
    }

    public void buttonClicked(ButtonEvent event) {
        System.out.println("Button clicked");
    }

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

class ButtonEvent {
    // Event data
}

4. 使用观察者模式：

import java.awt.*;
import java.awt.event.*;
import java.util.*;

public class MyButton extends Frame {
    private Button button;
    private List<ActionListener> listeners;

    public MyButton() {
        button = new Button("Click me");
        listeners = new ArrayList<ActionListener>();

        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                for (ActionListener listener : listeners) {
                    listener.actionPerformed(e);                }
            }
        });

        add(button);
        setSize(300, 200);
        setVisible(true);
    }

    public void addActionListener(ActionListener listener) {
        listeners.add(listener);
    }

    public static void main(String[] args) {
        MyButton myButton = new MyButton();
        myButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                System.out.println("Button clicked");
            }
        });
    }
}