Java开发网 - 怎么回事呀!快来帮忙呀!

Topic: 怎么回事呀!快来帮忙呀!

1.怎么回事呀!快来帮忙呀!

Posted by: kudo
Posted on: 2004-10-16 20:34

这个问题困扰我好几天了～拜托帮帮忙～
import java.awt.*;
import java.awt.event.*;
public class Change implements AdjustmentListener
{
  static Frame fra=new Frame("改变颜色");
  static Scrollbar scrRed=new Scrollbar(Scrollbar.HORIZONTAL,0,1,0,255);
  static Scrollbar scrGreen=new Scrollbar(Scrollbar.VERTICAL, 0, 1, 0, 255);
  static Scrollbar scrBlue=new Scrollbar(Scrollbar.VERTICAL, 0, 1, 0, 255);
  static Button btn=new Button();
  public static void main(String[] args)
  {  //设定各Scrollbar的初始植,取的是按钮btn的底色
    try{
    scrRed.setValue(btn.getBackground().getRed());
    scrGreen.setValue(btn.getBackground().getGreen());
    scrBlue.setValue(btn.getBackground().getBlue());}
    catch(Exception e)
    {};
    //注册事件监听器
    fra.addWindowListener(new MyWindowEvent());
    scrRed.addAdjustmentListener(new Change());
    scrGreen.addAdjustmentListener(new Change());
    scrBlue.addAdjustmentListener(new Change());
    fra.setLocation(100,100);
    //设定各控件的位置和大小
    btn.setBounds(120,120,150,150);
    scrRed.setBounds(120,50,150,30);
    scrGreen.setBounds(65,120,30,150);
    scrBlue.setBounds(300,120,30,150);
    //将各控件添加到fra上
    fra.add(scrRed);
    fra.add(scrGreen);
    fra.add(scrBlue);
    fra.add(btn);
    fra.setLayout(null);
    fra.setSize(400,350);
    fra.setVisible(true);
  }
  public void adjustmentValueChanged(AdjustmentEvent e)
  {  //使btn的底色随Scrollbar的变化而变化
    btn.setBackground(new Color(scrRed.getValue(),scrGreen.getValue(),scrBlue.getValue()));
  }
}
class MyWindowEvent extends WindowAdapter
{
  public void windowClosing(WindowEvent e)
  {
    System.exit(0);
  }
}
/*
如果把try　catch去掉，编译能通过，但运行出现以下错误：
java.lang.NullPointerException
  at Change.main(Change.java:12)
Exception in thread "main" Normal Termination
好像是null的异常～这个问题怎么解决呀？拜托了！！！！！
*/

2.Re:怎么回事呀!快来帮忙呀! [Re: kudo]	Copy to clipboard
Posted by: kavinwang Posted on: 2004-10-16 20:54 btn此时并没有设置背景，所以btn.getBackground()为null。你可以先设置btn的背景，Color.White

3.Re:怎么回事呀!快来帮忙呀! [Re: kudo]	Copy to clipboard
Posted by: kudo Posted on: 2004-10-16 20:58 好人呀！！！！谢谢kavinwang，怎么给你加分～～！！！

4.Re:怎么回事呀!快来帮忙呀! [Re: kudo]	Copy to clipboard
Posted by: kavinwang Posted on: 2004-10-16 21:01 我也不知道怎样加分，加的分有什么用处？

5.Re:怎么回事呀!快来帮忙呀! [Re: kudo]	Copy to clipboard
Posted by: nothing Posted on: 2004-10-16 21:10 关于加分,可以参看站务版.

6.Re:怎么回事呀!快来帮忙呀! [Re: kudo]	Copy to clipboard
Posted by: kavinwang Posted on: 2004-10-17 15:12 无所谓啦，如果觉得可以加分，就加啦，反正我的目的不在此。