HelloJava:Netscape的反戈一击

前言

一个简单的hello，java的图形化界面的入门程序。通过这个程序简单认识一下事件监听器和线程。在这里不做详细的说明，指体会监听器和线程的作用。

代码如下：

import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;

import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
/**
 * 运用线程实现字体闪烁
 * 运用MouseMotionListener接口的MouseDragged（）方法实现字符串的移动
 * 运用ActionListener接口的actionPerforme（）实现颜色的切换
 */


public class HelloJava {
    public static void main(String[] args) {
        JFrame frame = new JFrame("HelloJava");
        frame.add(new HelloComponent("Hello,java!")); 
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 300);
        frame.setVisible(true);
        
    }

}

class HelloComponent extends JComponent implements MouseMotionListener ,ActionListener,Runnable{
    String messages ;
    JButton button;
    int messagesx= 125;
    int messagesy = 95;
    int colorIndex;
    static Color[] someColors = {Color.black,Color.red,Color.green,Color.blue,Color.magenta};
    boolean blinkState;     //闪烁状态 
    public HelloComponent4(String messages) {
        this.messages=messages;
        button = new JButton("Change color");
        setLayout(new FlowLayout());
        add(button);
        button.addActionListener(this);
        addMouseMotionListener(this);
        Thread thread = new Thread(this);     //创建线程，用this把自身传进去
        thread.start();
    }
    
    public void paintComponent(Graphics g) {
        g.setColor(blinkState?getBackground():currentColor());  //为闪烁线程提供服务，根据blinkstates的值，在背景色和当前颜色之间切换，从而实现闪烁。
        g.drawString(messages, messagesx, messagesy);
    }
    
    public void actionPerformed(ActionEvent e) {
        if(e.getSource()== button)
            changeColor();
        
    }
    
    synchronized private void changeColor() {
        if(++colorIndex == someColors.length)     //先对索引加1在判断，可能会有溢出的危险
            colorIndex = 0;
        setForeground(currentColor());          //设置前背景色
        repaint();                 
    }
    
    synchronized private Color currentColor() {
        return someColors[colorIndex];
    }
    
    public void mouseMoved(MouseEvent e) {//MouseMotionListener接口中的方法，函数体为空也必须对其实现
        
    }
    
    public void mouseDragged(MouseEvent e) {
        messagesx = e.getX();
        messagesy = e.getY();
        repaint();
    }
    
    public void run() {//必须要有try进行捕获异常，否则会报错，此异常为中断异常InterruptedException
        try {
            while(true) {
                
        blinkState = !blinkState;
        repaint();
        Thread.sleep(300);          //线程睡眠时间为1/3秒，每秒钟闪烁3次
            }
        }catch (InterruptedException e) {
        }
    }
}