使用JScrollPane的问题，纵向的滚动条出不来？

[jindunfu]

import javax.swing.*;
import java.awt.*;

public class TestFlowLayout
extends JFrame {
JScrollPane jScrollPane1 = new JScrollPane();
JPanel jPanel1 = new JPanel();
FlowLayout flowLayout1 = new FlowLayout();
BorderLayout borderLayout1 = new BorderLayout();

public TestFlowLayout() {
try {
this.setSize(400, 300);
jbInit();
}
catch (Exception e) {
e.printStackTrace();
}
}

private void jbInit() throws Exception {
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
this.getContentPane().setLayout(borderLayout1);
jPanel1.setLayout(flowLayout1);
flowLayout1.setAlignment(FlowLayout.LEFT);
for (int i = 9; i < 69; i++) {
jPanel1.add(new JButton("JButton" + (i + 1)), null);
}
jPanel1.setPreferredSize(new Dimension(380, -1));
this.getContentPane().add(jScrollPane1, BorderLayout.CENTER);
jScrollPane1.getViewport().add(jPanel1, null);
}

public static void main(String[] args) {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
}
catch (Exception e) {
e.printStackTrace();
}
TestFlowLayout frame = new TestFlowLayout();
frame.setVisible(true);
}

}

[jindunfu]

怎么打家都没空吗？我都急死了。神呀 救救我！

[autowind]

加上这一句，jScrollPane1.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

添加横向的滚动条方法同上。

[hemiao_1993]

jPanel1.setPreferredSize(new Dimension(380, -1));
改为jPanel1.setPreferredSize(new Dimension(380, 380));就OK了

[fangwei1_2000]

测了下.
this.setSize(400, 300);
上面这句设置了300
下面的话不能小于265,低于这个数字好象就不行了.

[jindunfu]

to:autowind(一个人住真痛苦)
jScrollPane1.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);纵向的滚动条是有了，但不能滚动。jPanel1的内容也还是看不到。

to:hemiao_1993(冷血动物)
jPanel1.setPreferredSize(new Dimension(380, 380));后是能滚动了，但jPanel1的内容是动态的，这样好象不行的。

总之还是要谢谢二位。