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我有一個JComponent在JPanel內部沒有出現問題。JPanel沒有顯示任何東西
我使用Netbeans的Java GUI生成器部分構建GUI。 我得到了一個與GUI生成器一起構建的MainFrame類來處理菜單項。 我有一個MainPanel類，它在MainFrame類（菜單欄下）中。
然後我手動添加另一個JPanel到該MainPanel，這樣我就可以在沒有Netbeans GUI的情況下再次完全控制GUI。
但是，當我添加一個JButton到該JPanel然後沒有顯示出來。
MainFrame.java（包括Netbeans的代碼）：
package gui;
import javax.swing.JFrame;
/**
*
* @author Frank
*/
public class MainFrame extends javax.swing.JFrame {
/**
* Creates new form MainFrame
*/
public MainFrame() {
initComponents();
customInit();
}
private void customInit() {
this.setTitle("Trading Card Game");
this.setExtendedState(JFrame.MAXIMIZED_BOTH);
}
/**
* This method is called from within the constructor to initialize the form. WARNING: Do NOT
* modify this code. The content of this method is always regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents
private void initComponents() {
mainPanel1 = new gui.MainPanel();
jMenuBar1 = new javax.swing.JMenuBar();
menuFile = new javax.swing.JMenu();
menuFileQuit = new javax.swing.JMenuItem();
menuPreview = new javax.swing.JMenu();
menuPreviewStart = new javax.swing.JMenuItem();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
javax.swing.GroupLayout mainPanel1Layout = new javax.swing.GroupLayout(mainPanel1);
mainPanel1.setLayout(mainPanel1Layout);
mainPanel1Layout.setHorizontalGroup(
mainPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 400, Short.MAX_VALUE)
);
mainPanel1Layout.setVerticalGroup(
mainPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 279, Short.MAX_VALUE)
);
menuFile.setText("File");
menuFileQuit.setText("Quit");
menuFileQuit.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
menuFileQuitActionPerformed(evt);
}
});
menuFile.add(menuFileQuit);
jMenuBar1.add(menuFile);
menuPreview.setText("Preview");
menuPreviewStart.setText("Start");
menuPreview.add(menuPreviewStart);
jMenuBar1.add(menuPreview);
setJMenuBar(jMenuBar1);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(mainPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(mainPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
pack();
}// </editor-fold>//GEN-END:initComponents
private void menuFileQuitActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_menuFileQuitActionPerformed
System.exit(0);
}//GEN-LAST:event_menuFileQuitActionPerformed
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
new MainFrame().setVisible(true);
}
});
}
// Variables declaration - do not modify//GEN-BEGIN:variables
private javax.swing.JMenuBar jMenuBar1;
private gui.MainPanel mainPanel1;
private javax.swing.JMenu menuFile;
private javax.swing.JMenuItem menuFileQuit;
private javax.swing.JMenu menuPreview;
private javax.swing.JMenuItem menuPreviewStart;
// End of variables declaration//GEN-END:variables
}
MainPanel.java（包括Netbeans的代碼）：
package gui;
import java.awt.BorderLayout;
import java.awt.Color;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import model.Game;
/**
*
* @author Frank
*/
public class MainPanel extends javax.swing.JPanel {
/**
* Creates new form MainPanel
*/
public MainPanel() {
initComponents();
initPanel();
}
private void initPanel() {
this.setBorder(BorderFactory.createLineBorder(Color.yellow));
this.add(new JButton("Test"), BorderLayout.CENTER);
revalidate();
}
/**
* This method is called from within the constructor to initialize the form. WARNING: Do NOT
* modify this code. The content of this method is always regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents
private void initComponents() {
setLayout(new java.awt.BorderLayout());
}// </editor-fold>//GEN-END:initComponents
// Variables declaration - do not modify//GEN-BEGIN:variables
// End of variables declaration//GEN-END:variables
}
黃色邊框示出了圍繞所述的JPanel雖然。
任何線索爲什麼與「測試」的JButton沒有顯示出來？
圖片描述的情況（外觀無按鈕！）： no button http://img4.imageshack.us/img4/1466/so1l.jpg
問候。
另請參見[*我如何創建屏幕截圖？*]（http://meta.stackexchange.com/questions/99734/how-do-i-create-a-screenshot-to-illustrate-a -post） – trashgod 2013-04-09 17:30:42
你甚至想用這個說什麼？只是連接一些東西肯定不會解決一些我看不到的問題。 – skiwi 2013-04-09 17:32:00
你的桌面是不相關的，並且使用'setExtendedState（）'是多餘的。 – trashgod 2013-04-09 17:42:32