尽管我导入了applet库，但NetBeans无法在我的代码中识别和使用getDocumentBase（），我的项目中包含我的html文件以及所有其他所需文件，这里是我代码的一部分：
import java.awt.*;
import java.applet.*;
public class AirportCanvas extends Canvas
{
SingleLaneAirport controller;
Image redPlane;
Image bluePlane;
Image airport;
//AudioClip crashSound;
int[] redX,redY,blueX,blueY;
int maxCar = 2;
final static int initredX = 5;
final static int initredY = 55;
final static int initblueX = 410;
final static int initblueY = 130;
final static int bridgeY = 90;
boolean frozen = false;
int cycleTime = 20;
AirportCanvas(SingleLaneAirport controller)
{
super();
this.controller = controller;
// crashSound=controller.getAudioClip(controller.getDocumentBase(),"crash.au");
MediaTracker mt;
mt = new MediaTracker(this);
redPlane = controller.getImage(controller.getDocumentBase(), "redplane.png");
mt.addImage(redPlane, 0);
bluePlane = controller.getImage(controller.getDocumentBase(), "blueplane.png");
mt.addImage(bluePlane, 1);
airport = controller.getImage(controller.getDocumentBase(), "airport.png");
mt.addImage(airport, 2);
try
{
mt.waitForID(0);
mt.waitForID(1);
mt.waitForID(2);
}
catch (java.lang.InterruptedException e)
{
System.out.println("Couldn't load one of the images");
}
setSize(airport.getWidth(null),airport.getHeight(null));
init(1);
}
public final void init(int ncars)
{ //set number of cars
maxCar = ncars;
frozen = false;
redX = new int[maxCar];
redY = new int[maxCar];
blueX = new int[maxCar];
blueY = new int[maxCar];
for (int i = 0; i<maxCar ; i++)
{
redX[i] = initredX - i*85;
redY[i] = initredY;
blueX[i] =initblueX + i*85;
blueY[i] =initblueY;
}
repaint();
}
Image offscreen;
Dimension offscreensize;
Graphics offgraphics;
public void backdrop()
{
Dimension d = getSize();
if ((offscreen == null) || (d.width != offscreensize.width)
|| (d.height != offscreensize.height))
{
offscreen = createImage(d.width, d.height);
offscreensize = d;
offgraphics = offscreen.getGraphics();
offgraphics.setFont(new Font("Helvetica",Font.BOLD,36));
}
offgraphics.setColor(Color.lightGray);
offgraphics.drawImage(airport,0,0,this);
}
@Override
public void paint(Graphics g)
{
update(g);
}
@Override
public void update(Graphics g)
{
backdrop();
for (int i=0; i<maxCar; i++)
{
offgraphics.drawImage(redPlane,redX[i],redY[i],this);
offgraphics.drawImage(bluePlane,blueX[i],blueY[i],this);
}
if (blueY[0]==redY[0] && Math.abs(redX[0]+80 - blueX[0])<5)
{
offgraphics.setColor(Color.red);
offgraphics.drawString("Crunch!",200,100);
frozen=true;
// crashSound.play();
}
g.drawImage(offscreen, 0, 0, null);
}
//returns true for the period from just before until just after car on bridge
public boolean moveRed(int i) throws InterruptedException
{
int X = redX[i];
int Y = redY[i];
synchronized (this)
{
while (frozen )
wait();
if (i==0 || Math.abs(redX[i-1] - X) > 120)
{
X += 2;
if (X >=500)
{
X = -80; Y = initredY;
}
if (X >=60 && X < 290 && Y<bridgeY)
++Y;
if (X >=290 && Y>initredY)
--Y;
}
redX[i]=X;
redY[i]=Y;
repaint();
}
Thread.sleep(cycleTime);
return (X>25 && X<400);
}
//returns true for the period from just before until just after car on bridge
public boolean moveBlue(int i) throws InterruptedException
{
int X = blueX[i];
int Y = blueY[i];
synchronized (this)
{
while (frozen )
wait();
if (i==0 || Math.abs(blueX[i-1] - X) > 120)
{
X -= 2;
if (X <=-80)
{
X = 500; Y = initblueY;
}
if (X <=370 && X > 130 && Y>bridgeY)
--Y;
if (X <=130 && Y<initblueY)
++Y;
blueX[i]=X;
}
blueY[i]=Y;
repaint();
}
Thread.sleep(cycleTime);
repaint();
return (X>25 && X<400);
}
public synchronized void freeze()
{
frozen = true;
}
public synchronized void thaw()
{
frozen = false;
notifyAll();
}
}
单车道机场班：
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class SingleLaneAirport {
AirportCanvas display;
Button restart;
Button freeze;
Button onecar;
Button twocar;
Button threecar;
Checkbox fair;
Checkbox safe;
boolean fixed = false;
int maxCar = 1;
Thread red[];
Thread blue[];
@Override
public void init()
{
setLayout(new BorderLayout());
display = new AirportCanvas(this);
add("Center",display);
restart = new Button("Restart");
restart.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
display.thaw();
}
});
freeze = new Button("Freeze");
freeze.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
display.freeze();
}
});
onecar = new Button("One Car");
onecar.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
stop();
maxCar = 1;
start();
}
});
twocar = new Button("Two Cars");
twocar.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
stop();
maxCar = 2;
start();
}
});
threecar = new Button("Three Cars");
threecar.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
stop();
maxCar = 3;
start();
}
});
safe = new Checkbox("Safe",null,true);
safe.setBackground(Color.lightGray);
safe.addItemListener(new ItemListener()
{
public void itemStateChanged(ItemEvent e)
{
stop();
start();
}
});
fair = new Checkbox("Fair",null,false);
fair.setBackground(Color.lightGray);
fair.addItemListener(new ItemListener()
{
public void itemStateChanged(ItemEvent e)
{
stop();
start();
}
});
Panel p1 = new Panel();
p1.setLayout(new FlowLayout());
p1.add(freeze);
p1.add(restart);
p1.add(onecar);
p1.add(twocar);
p1.add(threecar);
p1.add(safe);
p1.add(fair);
add("South",p1);
setBackground(Color.lightGray);
}
@Override
public void start()
{
red = new Thread[maxCar];
blue = new Thread[maxCar];
display.init(maxCar);
Airport b;
if (fair.getState() && safe.getState())
b = new FairAirport();
else if ( safe.getState())
b = new SafeAirport();
else
b = new Airport();
for (int i = 0; i<maxCar; i++)
{
red[i] = new Thread(new RedPlane(b,display,i));
blue[i] = new Thread(new BluePlane(b,display,i));
}
for (int i = 0; i<maxCar; i++)
{
red[i].start();
blue[i].start();
}
}
@Override
public void stop()
{
for (int i = 0; i<maxCar; i++)
{
red[i].interrupt();
blue[i].interrupt();
}
}
}
答案 0 :(得分：2)
您的课程SingleLaneAirport应该扩展Applet课程，以便使用getDocumentBase()功能。
因为getDocumentBase()是Applet类的功能，而不是Object类