我出于某种原因，我不知道，我无法弄清楚如何改变椭圆的颜色。即使我把它们设置成红色和蓝色，它们仍保持黑色。谢谢你的帮助。
ControlPanel类
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.event.*;
import javax.swing.JFrame;
public class ControlPanel extends JPanel
{
private BallPanel ball1, ball2;
//declare all your components here
private JButton upR, downR, leftR, rightR, stopR, upB, downB, leftB, rightB, stopB;
private JSlider delayR, delayB;
private BallPanel redC, blueC;
private int DIAMETER = 30;
private JPanel redButtons, blueButtons, sliderR, sliderB, top, bottom, left, canvasCY;
private JLabel redDelay, blueDelay;
public ControlPanel(int width, int height)
{
width = 450;
height = 300;
//create 2 ball panels
redC = new BallPanel(0,10,Color.red,Color.cyan);
blueC = new BallPanel(0,10,Color.blue,Color.yellow);
//create 10 buttons
upR = new JButton("Up Red");
downR = new JButton("Down Red");
leftR = new JButton("Left Red");
rightR = new JButton("Right Red");
stopR = new JButton("Stop Red");
upB = new JButton("Up Blue");
downB = new JButton("Down Blue");
leftB = new JButton("Left Blue");
rightB = new JButton("Right Blue");
stopB = new JButton("Stop Blue");
//create 2 sliders
delayR=new JSlider(SwingConstants.VERTICAL,0,50,25);
delayB=new JSlider(SwingConstants.VERTICAL,0,50,25);
//add the corresponding listener to sliders and buttons
upR.addActionListener(new ButtonListener());
downR.addActionListener(new ButtonListener());
leftR.addActionListener(new ButtonListener());
rightR.addActionListener(new ButtonListener());
stopR.addActionListener(new ButtonListener());
upB.addActionListener(new ButtonListener());
downB.addActionListener(new ButtonListener());
leftB.addActionListener(new ButtonListener());
rightB.addActionListener(new ButtonListener());
stopB.addActionListener(new ButtonListener());
//organize 5 buttons into a panel using grid layout
redButtons= new JPanel(new GridLayout(5,1));
redButtons.add(upR);
redButtons.add(downR);
redButtons.add(leftR);
redButtons.add(rightR);
redButtons.add(stopR);
//organize 5 buttons into a panel using grid layout
blueButtons= new JPanel(new GridLayout(5,1));
blueButtons.add(upB);
blueButtons.add(downB);
blueButtons.add(leftB);
blueButtons.add(rightB);
blueButtons.add(stopB);
//create 2 labels
redDelay = new JLabel("Red Ball Delay");
blueDelay = new JLabel("Blue Ball Delay");
//organize a label and a slider into a panel using border layout
sliderR = new JPanel(new BorderLayout());
sliderR.add(redDelay, BorderLayout.NORTH);
sliderR.add(delayR, BorderLayout.SOUTH);
//organize the panel containing buttons and the panel with a slider
top = new JPanel(new GridLayout(1,2));
top.add(redButtons);
top.add(sliderR);
//organize a label and a slider into a panel using border layout
sliderB = new JPanel(new BorderLayout());
sliderB.add(blueDelay, BorderLayout.NORTH);
sliderB.add(delayB, BorderLayout.SOUTH);
//organize the panel containing buttons and the panel with a slider
bottom = new JPanel(new GridLayout(1,2));
bottom.add(blueButtons);
bottom.add(sliderB);
left=new JPanel(new GridLayout(2,1));
left.add(top);
left.add(bottom);
canvasCY = new JPanel(new GridLayout(2,1));
canvasCY.add(redC);
canvasCY.add(blueC);
JSplitPane sp = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, left, canvasCY);
setLayout(new GridLayout(0,1));
add(sp);
sp.setVisible(true);
}
//The ButtonListener class defines actions to be taken in case
//each of 10 buttons are pushed.
private class ButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent event)
{
Object action = event.getSource();
//if the up button for the red ball is pushed.
if (event.getSource() == upR)
redC.up();
else if (event.getSource() == downR)
redC.down();
else if (event.getSource() == leftR)
redC.left();
else if (event.getSource() == rightR)
redC.right();
else if (event.getSource() == stopR)
redC.suspend();
if (event.getSource() == upB)
blueC.up();
else if (event.getSource() == downB)
blueC.down();
else if (event.getSource() == leftB)
blueC.left();
else if (event.getSource() == rightB)
blueC.right();
else if (event.getSource() == stopB)
blueC.suspend();
}
} //end of ButtonListener
//The SliderListener defines actions to be taken in case
//each of the 2 sliders is moved by a user
private class SliderListener implements ChangeListener
{
public void stateChanged(ChangeEvent event)
{
}
} //end of SliderListener
}
BallPanel类
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.event.*;
import java.awt.Color;
import java.awt.Graphics;
public class BallPanel extends JPanel
{
int x;
int y;
Color ballColor;
Color backColor;
Timer timer;
int delay;
int stepX=3;
int stepY=0;
final int CIRCLE_DIAMETER = 20;
public BallPanel(int x, int y, Color ballColor, Color backColor)
{
this.x=x;
this.y=y;
this.ballColor=ballColor;
this.backColor=backColor;
delay=20;
stepX=3;
stepY=0;
timer= new Timer(delay, new MovingBallListener());
timer.start();
repaint();
}
public void up()
{
stepX=0;
stepY=-3;
repaint();
}
public void down()
{
stepX=0;
stepY=3;
repaint();
}
public void left()
{
stepX=-3;
stepY=0;
repaint();
}
public void right()
{
stepX=3;
stepY=0;
repaint();
}
public void suspend()
{
stepX=0;
stepY=0;
repaint();
}
public void setDelay(int delayNum)
{
timer.setDelay(delayNum);
}
public void paintComponent(Graphics page)
{
super.paintComponent(page);
page.fillOval(x,y,CIRCLE_DIAMETER,CIRCLE_DIAMETER);
page.setColor(ballColor);
setBackground(backColor);
}
private class MovingBallListener implements ActionListener
{
public void actionPerformed(ActionEvent event)
{
if (x > getSize().getWidth()-CIRCLE_DIAMETER && stepY == 0)
stepX=-3;
stepY=0;
repaint();
if(x < getSize().getWidth()-CIRCLE_DIAMETER && stepY == 0)
stepX=3;
stepY=0;
repaint();
}
}
}
作业12小程序
答案 0 :(得分：0)
我相信它与javadocs中的setColor
有关＆＃34;将此图形上下文的当前颜色设置为指定的颜色。使用此图形上下文的所有后续图形操作都使用此指定颜色。＆＃34;
所以翻转这个
page.fillOval(x,y,CIRCLE_DIAMETER,CIRCLE_DIAMETER);
page.setColor(ballColor);
是
page.setColor(ballColor);
page.fillOval(x,y,CIRCLE_DIAMETER,CIRCLE_DIAMETER);
这样你就可以用ballColor绘图了