哪里错了啊!请教,在线等 buttonPanel你没有声明啊。在构造方法前加一句:private Panel buttonPanel = new Panel(); 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 同楼上,修改如下:import java.awt.*;import java.net.*;public class Preload extends Frame{ public static void main(String[] args){ if (args.length==0){ System.out.println("Must Input arg"); System.exit(0); } if (args.length==2 && args[1].equals("-preload")) new Preload(args[0],true); else new Preload(args[0],false); }private TextField timeField;private long start=0;private boolean draw=false;private Image plate;private Panel buttonPanel = new Panel();//定义buttonPanel;public Preload(String imageFile,boolean preload){super("Preloading Images");buttonPanel.add(new Button("display Image"));timeField=new TextField(25);timeField.setEditable(false);buttonPanel.add(timeField);add("South",buttonPanel);registerImage(imageFile,preload);resize(1000,750);show();}public void paint(Graphics g){ if (draw){ g.drawImage(plate,0,0,this); showTime(); } }public boolean action(Event event,Object object){ draw=true; start=System.currentTimeMillis(); repaint(); return(true); }public boolean handleEvent(Event event){ if (event.id==Event.WINDOW_DESTROY) System.exit(0); return(super.handleEvent(event)); }private void registerImage(String imageFile,boolean preload){ try{plate=getToolkit().getImage(new URL(imageFile)); if(preload) prepareImage(plate,this); } catch(MalformedURLException mue){ System.out.println("Bad url:"+mue); } }private void showTime(){ timeField.setText("Elapsed Time:"+elapsedTime()+" seconds."); }private double elapsedTime(){ double delta=(double)(System.currentTimeMillis()-start); return(delta/1000.0); }} java swing 如何实现拖动文件到程序内识别路径 java有哪些方法是用C/C++实现的呢 求1到100前5个能整除3的数,能编译,运行没结果,怎么回事 执行时候缺少主方法和申明抽象 我要引入一个第三方包jdom.jar,必须在Class-Path中加上此包路径? 初学,Applet如何改变字体?头晕 求救,这个错误什么意思? 鼠标放在控件上的时候冒泡显示提示文字,鼠标离开才会消失?怎么做? 包的编译 关于环境变量配置问题 这个程序有些问题哈 System.out.println(4 + ' ' + 2);为何结果是38
import java.awt.*;
import java.net.*;
public class Preload extends Frame{
public static void main(String[] args){
if (args.length==0){
System.out.println("Must Input arg");
System.exit(0);
}
if (args.length==2 && args[1].equals("-preload"))
new Preload(args[0],true);
else
new Preload(args[0],false);
}
private TextField timeField;
private long start=0;
private boolean draw=false;
private Image plate;
private Panel buttonPanel = new Panel();//定义buttonPanel;public Preload(String imageFile,boolean preload){
super("Preloading Images");
buttonPanel.add(new Button("display Image"));
timeField=new TextField(25);
timeField.setEditable(false);
buttonPanel.add(timeField);
add("South",buttonPanel);
registerImage(imageFile,preload);
resize(1000,750);
show();
}
public void paint(Graphics g){
if (draw){
g.drawImage(plate,0,0,this);
showTime();
}
}
public boolean action(Event event,Object object){
draw=true;
start=System.currentTimeMillis();
repaint();
return(true);
}
public boolean handleEvent(Event event){
if (event.id==Event.WINDOW_DESTROY)
System.exit(0);
return(super.handleEvent(event));
}
private void registerImage(String imageFile,boolean preload){
try{plate=getToolkit().getImage(new URL(imageFile));
if(preload)
prepareImage(plate,this);
}
catch(MalformedURLException mue){
System.out.println("Bad url:"+mue);
}
}
private void showTime(){
timeField.setText("Elapsed Time:"+elapsedTime()+" seconds.");
}
private double elapsedTime(){ double delta=(double)(System.currentTimeMillis()-start);
return(delta/1000.0); }
}