我有一个从URL读取数据的程序使其成为BufferedImage并在JPanel上绘制它。但非常奇怪的错误，如图像切换等。这是我的代码：
package paraguay.cameras;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.Toolkit;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;
import java.net.URL;
import java.util.Timer;
import java.util.TimerTask;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.UIManager;
public class Paraguay_Cameras {
public static URL url1 = null;
public static URL url2 = null;
public static URL url3 = null;
public static URL url4 = null;
public static BufferedImage img1 = null;
public static BufferedImage img2 = null;
public static BufferedImage img3 = null;
public static BufferedImage img4 = null;
public static JPanel cam1 = null;
public static JPanel cam2 = null;
public static JPanel cam3 = null;
public static JPanel cam4 = null;
public static void main(String[] args) {
// UI
setLookAndFeelofNimbus();
// DIMESIONS
final Dimension screen_size = Toolkit.getDefaultToolkit()
.getScreenSize();
final int width = (int) screen_size.getWidth();
final int height = (int) screen_size.getHeight();
final Dimension sqr = new Dimension(width / 4, height / 4);
// TIMERS
Timer t = new Timer();
TimerTask reload = new TimerTask() {
@Override
public void run() {
try {
url1 = new URL(
"http://camaras.ultimahora.com/Camara/Centro.jpg?rand=12645");
url2 = new URL(
"http://camaras.ultimahora.com/Camara/tembetary.jpg?rand=6314");
url3 = new URL(
"http://camaras.ultimahora.com/Camara/recoleta.jpg?rand=15474");
url4 = new URL(
"http://camaras.ultimahora.com/Camara/elportal.jpg?rand=2599");
} catch (Exception exc) {
JOptionPane
.showMessageDialog(
null,
"Oh no! Looks like we can't connect to the internet!\nPlease try again...",
"", JOptionPane.ERROR_MESSAGE);
System.exit(0);
}
try {
img1 = ImageIO.read(url1);
} catch (Exception exc) {
JOptionPane
.showMessageDialog(
null,
"Uh, oh! Looks like we can't get the image in panel 1!\nSolution: Check your internet connection",
"", JOptionPane.ERROR_MESSAGE);
}
try {
img2 = ImageIO.read(url2);
} catch (Exception exc) {
JOptionPane
.showMessageDialog(
null,
"Uh, oh! Looks like we can't get the image in panel 2!\nSolution: Check your internet connection",
"", JOptionPane.ERROR_MESSAGE);
}
try {
img3 = ImageIO.read(url3);
} catch (Exception exc) {
JOptionPane
.showMessageDialog(
null,
"Uh, oh! Looks like we can't get the image in panel 3!\nSolution: Check your internet connection",
"", JOptionPane.ERROR_MESSAGE);
}
try {
img4 = ImageIO.read(url4);
} catch (Exception exc) {
JOptionPane
.showMessageDialog(
null,
"Uh, oh! Looks like we can't get the image in panel 4!\nSolution: Check your internet connection",
"", JOptionPane.ERROR_MESSAGE);
}
}
};
// JPANELS
cam1 = new JPanel() {
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.drawImage(img1, 0, 0, null);
}
};
cam1.setPreferredSize(sqr);
cam2 = new JPanel() {
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.drawImage(img2, 0, 0, null);
}
};
cam2.setPreferredSize(sqr);
cam3 = new JPanel() {
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.drawImage(img3, 0, 0, null);
}
};
cam3.setPreferredSize(sqr);
cam4 = new JPanel() {
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.drawImage(img4, 0, 0, null);
}
};
cam4.setPreferredSize(sqr);
JPanel main = new JPanel(new GridLayout(2, 2));
main.add(cam1);
main.add(cam2);
main.add(cam3);
main.add(cam4);
main.setBackground(Color.WHITE);
// JFRAME
JFrame window = new JFrame("Paraguay Cameras");
window.setSize(width, height);
window.add(main);
window.setVisible(true);
window.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
window.setLocationRelativeTo(null);
window.setResizable(true);
window.setAlwaysOnTop(true);
window.setEnabled(true);
window.addWindowListener(new WindowAdapter() {
@Override
public void windowClosing(WindowEvent we) {
System.exit(0);
}
});
t.schedule(reload, 0, 4000);
cam1.repaint();
cam2.repaint();
cam3.repaint();
cam4.repaint();
}
public static void setLookAndFeelofNimbus() {
try {
UIManager
.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
} catch (Exception exc) {
JOptionPane
.showMessageDialog(
null,
"Oops! Looks like we can't use the UI (User Interface) of Nimbus...",
"", JOptionPane.ERROR_MESSAGE);
}
}
}
任何人都可以帮我修复我的错误吗？谢谢！
答案 0 :(得分：1)
加载图像后，您永远不会重新绘制面板。坦率地说，在目前的代码中很难实现这一点。重构代码，以便在重新加载图像后调用main.repaint();来刷新面板。另外，请不要忘记在super.paintComponents(g);实施中致电paintComponent()。
另一点，对于Swing，最好使用javax.swing.Timer。有关详细信息，请参阅How to Use Swing Timers。
另请注意，在这种情况下调用setPreferredSize()将无效，因为您正在使用GridLayout。一般来说，应该主要避免使用setPreferredSize()，请参阅Should I avoid the use of set[Preferred|Maximum|Minimum]Size methods in Java Swing?