java事件处理

1.ActionEven事件

文本框，按钮，菜单项，密码框，单选按钮都可以出发ActionEvent事件

使用

addActionListener(ActionListener listen1)

来注册监视器

ActionListener本来是一个接口，我们必须写类（或者其他接口）来实现它的唯一方法

actionPerformed(ActionEvent e)

这里的e是事件源给该方法的一个参数，ActionEvent类有两个方法

public Object getSource();//返回事件源的上转型对象的引用
public String getActionCommand()//返回一个相关的“命令”字符串，比如这个ActionEvent是文本框，那就是返回他的文本内容

统计单词字数的一个代码

class Component extends JFrame{
    JTextField test1;
    JButton button1;
    JTextArea testArea1;
    JRadioButton radioButton1,radioButton2;
    ButtonGroup group1;
    Component(){
        init();
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    void init(){
        setLayout(new FlowLayout());
        test1=new JTextField(8);
        button1=new JButton("huang");
        testArea1=new JTextArea(8,24);
        add(test1);
        add(button1);
        add(new JScrollPane(testArea1));
        AListener a=new AListener(test1,button1,testArea1);
        test1.addActionListener(a);//需要import java.awt.event.ActionListener;
        button1.addActionListener(a);
    }
}

class AListener implements ActionListener{
    JTextField test1;
    JButton button1;
    JTextArea testArea1;
    AListener(JTextField test,JButton button,JTextArea testArea){
        test1=test;
        button1=button;
        testArea1=testArea;
    }
    public void actionPerformed(ActionEvent e){
        String a=test1.getText();
        testArea1.append(a+"的长度"+a.length());
    }
}

---

 ItemEvent事件

选择框和下拉列表都可以触发ItemEvent事件

注册监视器

addItemListener(ItemListener listen1)

ItemListener接口也只有一个

对应事件触发的,可以用 combo1.getSelectedItem()获得事件的事件源

public void itemStateChanged(ItemEvent e)

简单计算器代码，（有个bug，下拉框要换了其他才能激活

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.InputEvent;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.KeyEvent;
public class test{

    public static void main(String args[]){
        Component window1=new Component();
        window1.setBounds(40,40,300,200);
    }
}

class Component extends JFrame{
    JTextField test1,test2;
    JButton button1;
    JTextArea testArea1;
    JRadioButton radioButton1,radioButton2;
    ButtonGroup group1;
    JComboBox combo1;
    Component(){
        init();
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    void init(){
        setLayout(new FlowLayout());
        test1=new JTextField(4);
        test2=new JTextField(4);
        button1=new JButton("go");
        testArea1=new JTextArea(5,20);
        combo1=new JComboBox();
        combo1.addItem("+");
        combo1.addItem("-");
        combo1.addItem("*");
        combo1.addItem("/");
        add(test1);
        add(combo1);
        add(test2);
        add(button1);
        add(new JScrollPane(testArea1));
        Computer computer1=new Computer(test1,test2,testArea1);
        Fuhao fuhao1=new Fuhao(computer1,combo1);
        combo1.addItemListener(fuhao1);
        button1.addActionListener(computer1);
    }
}
class Fuhao implements ItemListener{
    Computer computer1;
    JComboBox combo1;
    Fuhao(Computer a,JComboBox b){
        computer1=a;
        combo1=b;
    }
    public void itemStateChanged(ItemEvent e){
//        System.out.println(combo1.getSelectedItem().toString());
        computer1.getFuhao(combo1.getSelectedItem().toString());
    }
}
class Computer implements ActionListener{
    JTextField a,b;
    JTextArea c;
    String fuhao;
    double result;
    void getFuhao(String a){
        fuhao=a;
    }
    Computer(JTextField a,JTextField b,JTextArea c){
        this.a=a;
        this.b=b;
        this.c=c;
    }
    public void actionPerformed(ActionEvent e){
        try{
//            System.out.println(fuhao);
//            System.out.println(a.getText());
//            System.out.println(b.getText());
            double a1=Double.parseDouble(a.getText());
            double b1=Double.parseDouble(b.getText());
            if(fuhao.equals("+")){
                result=a1+b1;
            }else if(fuhao.equals("-")){
                result=a1-b1;
            }else if(fuhao.equals("*")){
                result=a1*b1;
            }else if(fuhao.equals("/")){
                result=a1/b1;
            }
            c.append(a1+" "+fuhao+" "+b1+"="+" "+result+"
");
        }
        catch(Exception exp){
            c.append("
请输入数字
");
        }
    }
}