点击按钮，你可以根据面板大小添加新的按钮。在这张图片中，无法看到垂直滚动条，这就是问题所在。
我使用的代码是以下代码：
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package ScrollPanelTest;
import java.awt.ComponentOrientation;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JScrollBar;
/**
*
* @author leandro.lima
*/
public class ScrollPane extends javax.swing.JFrame {
public int count = 1;
private WrapLayout layout = new WrapLayout(FlowLayout.LEADING, 5, 5);
/**
* Creates new form ScrollPane
*/
public ScrollPane() {
initComponents();
}
/**
* 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">
private void initComponents() {
jButton1 = new javax.swing.JButton();
jScrollPane1 = new javax.swing.JScrollPane();
jPanel1 = new javax.swing.JPanel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jButton1.setText("jButton1");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
jPanel1.setBackground(new java.awt.Color(255, 255, 255));
jPanel1.setMinimumSize(new java.awt.Dimension(0, 0));
jPanel1.setPreferredSize(new java.awt.Dimension(0, 0));
java.awt.FlowLayout flowLayout1 = new java.awt.FlowLayout();
flowLayout1.setAlignOnBaseline(true);
jPanel1.setLayout(flowLayout1);
jScrollPane1.setViewportView(jPanel1);
jPanel1.setComponentOrientation(ComponentOrientation.LEFT_TO_RIGHT);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addComponent(jButton1)
.addContainerGap(327, Short.MAX_VALUE))
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jScrollPane1))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap(163, Short.MAX_VALUE)
.addComponent(jButton1))
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addComponent(jScrollPane1)
.addGap(34, 34, 34)))
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
final JButton button = new JButton();
button.setPreferredSize(new Dimension(100, 100));
button.setSize(new Dimension(100, 100));
button.setAction(new AbstractAction("<html><center><h4>Button " + (count++) + "</h4><br>Remove me</center></html>") {
@Override
public void actionPerformed(ActionEvent ae) {
jPanel1.remove(button);
jPanel1.getRootPane().repaint();
getContentPane().repaint();
}
});
jPanel1.add(button);
jPanel1.getRootPane().repaint();
getContentPane().repaint();
}
/**
* @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 ("Windows".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | javax.swing.UnsupportedLookAndFeelException ex) {
}
//</editor-fold>
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new ScrollPane().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JPanel jPanel1;
private javax.swing.JScrollPane jScrollPane1;
// End of variables declaration
}
Obs：我找不到添加按钮时重新绘制面板的方法，如果你知道，请也给我看看。
谢谢！
jPanel1.setLayout(flowLayout1);
jScrollPane1.setViewportView(jPanel1);
您正在面板中使用FlowLayout。FlowLayout不会重新计算面板的首选大小。由于首选大小永远不会改变，垂直滚动条将永远不会出现。
这就是为什么您需要在面板上使用WrapLayout。
您定义了一个WrapLayout变量，但您从未在面板上实际使用过WrapLayout。
另外，我不知道你为什么要使用GroupLayout来做这么简单的事情。框架的默认布局管理器是BorderLayout。只需使用面板创建滚动窗格，并将滚动窗格添加到BorderLayout.CENTER。然后您将包含按钮的另一个面板添加到BorderLayout。PAGE_END。它的两行代码。学习您创建自己的GUI，不要依赖IDE生成的复杂代码。
当按钮被添加时，我找不到重新绘制面板的方法，如果你知道，请告诉我。
从可见GUI添加（或删除）组件时，基本代码如下：
panel.add(...);
panel.revalidate();
panel.repaint();
