import java.awt.GridLayout;
import java.awt.Label;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class WelcomeJFrame extends JFrame {
/**
*
*/
private static final long serialVersionUID = 1L;
public WelcomeJFrame (String texts[]) {
super("滚动字");
this.setBounds(300, 240, 400, 300);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
if(texts==null||texts.length==0)
this.getContentPane().add(new GuopengJPanel("welcome"));
else {
this.getContentPane().setLayout(new GridLayout(texts.length, 1));
for(int i=0;i<texts.length;i++)
this.getContentPane().add(new GuopengJPanel(texts[i]));
}
this.setVisible(true);
}
public WelcomeJFrame() {
this(null);
}
private class GuopengJPanel extends JPanel implements ActionListener,Runnable {
/**
*
*/
private static final long serialVersionUID = 1L;
JTextField text_word,text_sleep,text_state=null;
JButton button_start,button_interrupt;
Thread thread;
int sleeptime;
GuopengJPanel(String text) {
this.setLayout(new GridLayout(2,1));
text_word =new JTextField(String.format("%115s", text));
this.add(text_word);
JPanel panel_sub=new JPanel();
this.add(panel_sub);
panel_sub.add(new Label("sleep"));
this.sleeptime=(int)(Math.random()*100);
text_sleep=new JTextField(""+sleeptime,5);
panel_sub.add(text_sleep);
text_sleep.addActionListener(this);
button_start=new JButton("启动");
panel_sub.add(button_start);
button_start.addActionListener(this);
button_interrupt=new JButton("中断");
panel_sub.add(button_interrupt);
button_interrupt.addActionListener(this);
thread =new Thread(this);
button_interrupt.setEnabled(false);
panel_sub.add(new JLabel("state"));
text_state=new JTextField(""+thread.getState(),10);
text_state.setEditable(false);
panel_sub.add(text_state);
}
public void run() {
while (true) {
String str = text_word.getText();
text_word.setText(str.substring(3)+str.substring(0,3));
try {
Thread.sleep(sleeptime);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
break;
}
}
}
@Override
public void actionPerformed(ActionEvent e) {
if(e.getSource()==button_start){
thread= new Thread(this);
thread.start();
text_state.setText(""+thread.getState());
button_start.setEnabled(false);
button_interrupt.setEnabled(true);
}
if (e.getSource()==button_interrupt) {
thread.interrupt();
text_state.setText(""+thread.getState());
button_start.setEnabled(true);
button_interrupt.setEnabled(false);
}
if (e.getSource()==text_sleep) {
try{
sleeptime=Integer.parseInt(text_sleep.getText());}
catch(NumberFormatException nfex)
{JOptionPane.showMessageDialog(this, "\""+text_sleep.getText()+"\"不能转换成整数，请重新输入！");}
}
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
String texts[]={"welcome","hello","Guopeng","handsome"};
new WelcomeJFrame(texts);
}
}
text_word.setText(str.substring(3)+str.substring(0,3));求这段滚动实现代码的解释 我有点转不过来
分析代码可以看到，text_word的初始化时是有115个空格+指定字符串的，而这行代码则是将0到3位置处的空格移到字符串尾部，第三个空格以后的信息提到前面，给人的错觉就是非空格字符串前移了。
主要代码是这个初始化代码:
//以hello为例，初始化值是：115个空格+hello
text_word =new JTextField(String.format("%115s", text));
//线程循环run中执行，下面这行代码则将文本值设置为：112个空格+hello
text_word.setText(str.substring(3)+str.substring(0,3));
这行主要代码给人的感觉就是hello这个字符串每次都往前挪动了3个字符的位置，线程在循环执行该操作，知道hello到达首部为止。