我正在尝试使用 Netbeans 用 Java 制作图形界面。我使用JFrame Form。在其中，一个JScrollPane包含一个JPanel。在JScrollPane中，为属性verticalScrollBarPolicy分配了值“AS_NEEDED”，以便仅在内容太大时滚动。
但我的问题是垂直滚动条从应用程序开始就存在。如何解决？
我将setLayout方法放在我的JPanel的构造函数中（之前在我的jMenuItem1ActionPerformed方法中），它似乎可以工作。
但是，我还有另一个小问题。当我打开几个文件时，一个太大的间隙将它们分开（当有很多文件时情况并非如此）。
下面是可视化的 IHM、JPanel和JScrollPane的属性以及生成的代码。
public class Items_IHM extends javax.swing.JFrame {
JCheckBox checkBox;
List<JCheckBox> listOfCheckBox = new ArrayList<>();
File[] allFiles;
File folder;
/**
* Creates new form Items_IHM
*/
public Items_IHM() {
initComponents();
panel.setLayout(new GridLayout(0, 1, 10, 10));
this.setLocationRelativeTo(null);
}
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents
private void initComponents() {
srollPane = new javax.swing.JScrollPane();
panel = new javax.swing.JPanel();
buttonExecute = new javax.swing.JButton();
jMenuBar1 = new javax.swing.JMenuBar();
jMenu1 = new javax.swing.JMenu();
jMenuItem1 = new javax.swing.JMenuItem();
jMenuItem2 = new javax.swing.JMenuItem();
jMenu2 = new javax.swing.JMenu();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
srollPane.setHorizontalScrollBarPolicy(javax.swing.ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
srollPane.setMinimumSize(new java.awt.Dimension(300, 400));
srollPane.setPreferredSize(new java.awt.Dimension(200, 300));
javax.swing.GroupLayout panelLayout = new javax.swing.GroupLayout(panel);
panel.setLayout(panelLayout);
panelLayout.setHorizontalGroup(
panelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 339, Short.MAX_VALUE)
);
panelLayout.setVerticalGroup(
panelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 477, Short.MAX_VALUE)
);
srollPane.setViewportView(panel);
buttonExecute.setText("Execute");
buttonExecute.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
buttonExecuteActionPerformed(evt);
}
});
jMenu1.setText("Fichier");
jMenuItem1.setAccelerator(javax.swing.KeyStroke.getKeyStroke(java.awt.event.KeyEvent.VK_O, java.awt.event.InputEvent.CTRL_MASK));
jMenuItem1.setText("Ouvrir");
jMenuItem1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jMenuItem1ActionPerformed(evt);
}
});
jMenu1.add(jMenuItem1);
jMenuItem2.setAccelerator(javax.swing.KeyStroke.getKeyStroke(java.awt.event.KeyEvent.VK_Q, java.awt.event.InputEvent.CTRL_MASK));
jMenuItem2.setText("Quitter");
jMenuItem2.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jMenuItem2ActionPerformed(evt);
}
});
jMenu1.add(jMenuItem2);
jMenuBar1.add(jMenu1);
jMenu2.setText("Editer");
jMenuBar1.add(jMenu2);
setJMenuBar(jMenuBar1);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(buttonExecute, javax.swing.GroupLayout.PREFERRED_SIZE, 90, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap())
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(srollPane, javax.swing.GroupLayout.PREFERRED_SIZE, 341, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(99, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(srollPane, javax.swing.GroupLayout.PREFERRED_SIZE, 479, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(buttonExecute, javax.swing.GroupLayout.DEFAULT_SIZE, 31, Short.MAX_VALUE)
.addContainerGap())
);
pack();
}// </editor-fold>//GEN-END:initComponents
private void jMenuItem1ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jMenuItem1ActionPerformed
Preferences preferences = Preferences.userRoot();
String path = preferences.get("DEFAULT_PATH", "");
JFileChooser fileChooser = new JFileChooser();
fileChooser.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
fileChooser.setCurrentDirectory(new File(path));
int returnVal = fileChooser.showOpenDialog(null);
if (returnVal == JFileChooser.APPROVE_OPTION) {
// allNameFilesTextArea.setText("");
folder = fileChooser.getSelectedFile();
fileChooser.setCurrentDirectory(folder);
preferences.put("DEFAULT_PATH", folder.getAbsolutePath());
allFiles = folder.listFiles(new FilenameFilter() {
public boolean accept(File folder, String name) {
return name.toLowerCase().endsWith(".csv");
}
});
listOfCheckBox.clear();
panel.removeAll();
panel.revalidate();
panel.repaint();
for (int i = 0; i < allFiles.length; i++) {
checkBox = new JCheckBox(allFiles[i].getName());
listOfCheckBox.add(checkBox);
panel.add(checkBox);
}
}
}//GEN-LAST:event_jMenuItem1ActionPerformed
private void buttonExecuteActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_buttonExecuteActionPerformed
Items_Application itemsApp;
try {
if (listOfCheckBox.size() > 0) {
itemsApp = new Items_Application(folder.getPath());
for (int i = 0; i < listOfCheckBox.size(); i++) {
if (listOfCheckBox.get(i).isSelected()) {
itemsApp.loadInItem(allFiles[i].getPath());
}
}
itemsApp.buildListOfItemsWithSamePartNb();
itemsApp.buildListOfItemsWithSameThalesNb();
itemsApp.writeOutItems(folder.getPath());
}
} catch (IOException ex) {
ex.printStackTrace();
}
}//GEN-LAST:event_buttonExecuteActionPerformed
private void jMenuItem2ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jMenuItem2ActionPerformed
System.exit(0);
}//GEN-LAST:event_jMenuItem2ActionPerformed
/**
* @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(Items_IHM.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(Items_IHM.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Items_IHM.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Items_IHM.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Items_IHM().setVisible(true);
}
});
}