我试图在JFrame上的JPanel上绘制一个简单的矩形，但它没有用。有人可以给我一些建议吗？如果有人可以，我会很高兴...我真的很努力，但我无法弄清楚如何做到这一点。这段代码是我的“Snake”程序的一部分。所有其他工作，除此之外。这是我的代码：
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();
}
}
}
答案 0 :(得分：0)
从JFrame中删除paintComponent。这也称为super.paint i.o. super.paintComponent方法。
pnlpnl = new JPanel() {
@Override
public void paintComponent(Graphics gr) {
super.paintComponent(gr);
gr.setColor(Color.CYAN);
gr.fillRect(0, 0, 200, 200);
}
};
在此paintComponent中，您可以使用JFrame的字段。
在构造函数中调用initStartFrame时，它不应该是可覆盖的（然后将调用子类的版本，而不会完全初始化子类）。
//Sometimes: public final void initStartFrame(String name) {
private void initStartFrame(String name) {
按原样启动框架：
// GUI
frame.validate();
//frame.repaint();
frame.pack();
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
frame.setVisible(true);
}
});