如何将jbutton添加到jscrollpane

Question

hy, i am trying to add multiple jbuttons to the pane and want to scroll them. so what i done is first added buttons to the jpanel than that jpanel to the jscrollpane than jscrollpane to the another jpanel and so on. but the promblem i am getting is buttons is showing but there is not scroll bar to scroll the pane and see all the buttons.

import java.awt.*;

import javax.swing.*;

import java.awt.event.*;

class ICFTWindow extends JFrame

{
JPanel mainPanel,userlistPanel,chatPanel,userlistPanel2;
JButton checkButton,button2,button3,button4,button5,button6;
JScrollPane scrollpane;
JScrollBar scrollbar;

ICFTWindow()
{
    mainPanel = new JPanel();
    mainPanel.setLayout(null);

    userlistPanel = new JPanel(new FlowLayout());
    userlistPanel.setBounds(0,0,160,270);
    userlistPanel2 = new JPanel();
    userlistPanel2.setBounds(0,0,100,270);
    userlistPanel2.setLayout(new BorderLayout());

    scrollpane = new JScrollPane(userlistPanel);

    checkButton = new JButton();
    checkButton.setPreferredSize(new Dimension(90, 50));

    button2 = new JButton();
    button2.setPreferredSize(new Dimension(90, 50));

    button3 = new JButton();
    button3.setPreferredSize(new Dimension(90, 50));

    button4 = new JButton();
    button4.setPreferredSize(new Dimension(90, 50));

    button5 = new JButton();
    button5.setPreferredSize(new Dimension(90, 50));

    button6 = new JButton();
    button6.setPreferredSize(new Dimension(90, 50));

    userlistPanel.setBorder(BorderFactory.createLineBorder(Color.black));

    scrollpane.add(userlistPanel);
    mainPanel.add(userlistPanel);

    userlistPanel.add(button2);
    userlistPanel.validate();
    userlistPanel.add(checkButton);
    userlistPanel.validate();
    userlistPanel.add(button3);
    userlistPanel.validate();
    userlistPanel.add(button4);
    userlistPanel.validate();
    userlistPanel.add(button5);
    userlistPanel.validate();
    userlistPanel.add(button6);
    userlistPanel.validate();

    userlistPanel.validate();
    userlistPanel2.add(scrollpane);
    mainPanel.add(userlistPanel2);
    add(mainPanel);
    setSize(500,300);
    setVisible(true);

}

public static void main(String args[])
{
    new ICFTWindow();
}
}

Answer 1

Delete these two lines:

scrollpane.add(userlistPanel);
mainPanel.add(userlistPanel);

You don't need to add the JPanel (for which you want a scroll bar) to the JScrollPane . It is enough to send it to the constructor of the scroll pane.

After that, you have to add the scroll pane to the top level component and it will also add the panel contained within and put a scroll bar on it. See here for more details on how to use scroll panes.