在Swing中使用具有绝对布局的滚动条

Question

I am not able to use scroll bars with absolute layout in Swing.

I don't wish to use this layout but I have to display dynamic objects on my panel on click of a button and align them using setBounds which can be done using this layout only (I guess).

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

public class clothes2 extends javax.swing.JFrame {

    JTextField n=null;
    JButton m=null;

    public clothes2(){
        initComponents();
    }

    public void initComponents() {
        Container contentPane = getContentPane();
        contentPane.setLayout(new BorderLayout());
        final JPanel jp = new JPanel();
        contentPane.setPreferredSize(new Dimension(320,200));
        jp.setLayout(null);
        m=new JButton("add");
        m.setBounds(0,0,50,50);
        jp.add(m);
        m.addMouseListener( new MouseAdapter() {

            int x=0;
            int y=0;

            public void mouseClicked(MouseEvent me){
                x+=100;
                y+=100;
                jp.add(n=new JTextField("Name"));
                n.setBounds(x, y, 50, 50);
                jp.add(n=new JTextField("code"));
                x+=100;
                n.setBounds(x,y, 50, 50);
                jp.revalidate();
                jp.repaint();
                x=0;
            }
        });

        int v = ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS;
        int h = ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS;
        JScrollPane jsp = new JScrollPane(jp, v, h);
        contentPane.add(jsp, BorderLayout.CENTER);
    }

    public static void main(String args[]) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                JFrame f= new clothes2();
                f.setVisible(true);
                f.setSize(640,320);
            }
        });
    }
}

Answer 1

display dynamic objects .. which can be done using this layout only (I guess).

You guess wrong.

See this GUI , that can not only change PLAFs at run-time, but also dynamically add new components ¹ . Click to..

Add Another Label

1. This example adds the new labels to a GridLayout - but the principle is the same for any layout (or any component).

Answer 2

设置容器的首选大小。

Answer 3

JScrollBar uses the preferred size of the component inside it to determine how large the scroll bars should be, and if they should be displayed.

Usually, the layout manager handles this using the preferredLayoutSize method. This can be overriden by explicitly setting the preferred size of the component.

So either you have to set the preferred size, or use a custom layout manager that calculates it for you.

see also here

might help you.

Answer 4

添加布局
jp.setLayout(new FlowLayout());