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我试图在JPanel上绘制一个简单的矩形，但是它并不工作。有人可以给我一些建议吗？如果有人能......我会很高兴，我真的很努力，但我不知道该怎么做。这段代码是我的“蛇”程序的一部分。除此之外，其余所有工作都是有效的。这里是我的代码：在JPanel上绘制图形（Graphics gr）
package initialising_Package;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class Initialising extends JPanel implements WindowListener,
ItemListener, ChangeListener, Runnable {
/**
* @param args
*/
private String name;
private JFrame frame;
private boolean fall = false;
private JSlider slider;
private JLabel lbl1, lbl2, lbl3, lbl4;
private JComboBox box1, box2, box3;
private String[] positionsx, positionsy, laenge;
private JPanel pnl1, pnl2, pnl3, pnlpnl;
private JButton btn;
private int beginningLenght, posX, posY;
private boolean start = false;
public Initialising() {
initStartFrame("Initialising");
}
public void initStartFrame(String name) {
frame = new JFrame(name);
frame.setLocation(300, 300);
frame.setSize(500, 350);
frame.setUndecorated(false);
frame.getContentPane().setLayout(new GridLayout(5, 1));
frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
frame.setVisible(true);
frame.addWindowListener(this);
// GUI
slider = new JSlider(1, 100, 50);
slider.addChangeListener(this);
slider.setPaintTicks(false);
slider.setPaintTrack(true);
positionsx = new String[50];
positionsy = new String[50];
for (int i = 0, j = 0; i < 50; i++, j = j + 10) {
positionsx[i] = new String("" + j);
positionsy[i] = new String("" + j);
}
laenge = new String[45];
for (int i = 0; i < 45; i++) {
laenge[i] = "" + (i + 1);
}
box1 = new JComboBox(positionsx);
box1.addItemListener(this);
box2 = new JComboBox(positionsy);
box2.addItemListener(this);
box3 = new JComboBox(laenge);
box3.addItemListener(this);
lbl1 = new JLabel("Geschwindigkeit: ");
lbl2 = new JLabel("Startlaenge: ");
lbl3 = new JLabel("Position: ");
pnlpnl = new JPanel();
pnlpnl.setPreferredSize(new Dimension(95, 490));
pnlpnl.setBackground(Color.BLACK);
pnl1 = new JPanel();
pnl1.setLayout(new GridLayout(1, 2));
pnl2 = new JPanel();
pnl2.setLayout(new GridLayout(1, 2));
pnl3 = new JPanel();
pnl3.setLayout(new GridLayout(1, 3));
btn = new JButton("Snake!");
btn.setPreferredSize(new Dimension(80, 490));
pnl1.add(lbl1);
pnl1.add(slider);
pnl2.add(lbl2);
pnl2.add(box3);
pnl3.add(lbl3);
pnl3.add(box1);
pnl3.add(box2);
frame.add(pnlpnl);
frame.add(pnl1);
frame.add(pnl2);
frame.add(pnl3);
frame.add(btn);
// GUI
frame.validate();
frame.repaint();
}
public int getSpeed() {
return slider.getValue();
}
public int getBeginningLenght() {
return beginningLenght;
}
public int getPosX() {
return posX;
}
public int getPosY() {
return posY;
}
@Override
public void windowActivated(WindowEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void windowClosed(WindowEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void windowClosing(WindowEvent arg0) {
int z = JOptionPane.showConfirmDialog(frame,
"Willst du wirklich benden?", "Warnung", 0);
if (z == JOptionPane.YES_OPTION) {
System.exit(0);
}
}
@Override
public void windowDeactivated(WindowEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void windowDeiconified(WindowEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void windowIconified(WindowEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void windowOpened(WindowEvent arg0) {
// TODO Auto-generated method stub
}
public static void main(String[] args) {
// TODO Auto-generated method stub
Initialising init = new Initialising();
new Thread(init).start();
}
@Override
public void itemStateChanged(ItemEvent e) {
// TODO Auto-generated method stub
if (e.getSource().equals(box1)) {
posX = Integer.parseInt((String) box1.getSelectedItem());
System.out.println("PosX: " + posX);
} else if (e.getSource().equals(box2)) {
posY = Integer.parseInt((String) box2.getSelectedItem());
System.out.println("PosY: " + posY);
} else if (e.getSource().equals(box3)) {
beginningLenght = Integer.parseInt((String) box3.getSelectedItem());
System.out.println("Beginning Lenght: " + beginningLenght);
System.out.println("H: " + pnlpnl.getHeight() + " B: "
+ pnlpnl.getWidth());
}
}
@Override
public void stateChanged(ChangeEvent e) {
// TODO Auto-generated method stub
if (e.getSource().equals(slider)) {
System.out.println("Speed: " + slider.getValue());
}
}
@Override
public void paintComponent(Graphics gr) {
super.paint(gr);
gr.setColor(Color.CYAN);
gr.fillRect(0, 0, 200, 200);
}
@Override
public void run() {
// TODO Auto-generated method stub
while (true) {
System.out.println("It works!!");
try {
Thread.sleep(800);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (!start) {
}
repaint();
validate();
}
}
}
如果这是不是有问题（我没有看过它），那么你将有更好的运气得到一个答案最短的代码示例一个简短的例子。 – LJNielsenDk