Probably an easy problem with a JScrollPane

Question

Hi,
I would like to scroll a JScrollPane from outside my JScrollPane, of course I could used the setValue of the JScrollBar but I would prefer to simulate a click on the up/down buttons of my bar. Does anyone can help me?
Thanks.
S�bastien

Answer 1

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class souptier extends JFrame implements ActionListener {
  JScrollPane scrollPane;
  JButton
    upButton,
    downButton;
  JRadioButton
    unitButton,
    blockButton;
  public souptier() {
    upButton = new JButton("Up");
    upButton.addActionListener(this);
    downButton = new JButton("Down");
    downButton.addActionListener(this);
    ButtonGroup group = new ButtonGroup();
    unitButton = new JRadioButton("unit");
    group.add(unitButton);
    blockButton = new JRadioButton("block");
    blockButton.setSelected(true);
    group.add(blockButton);
    JPanel buttonPanel = new JPanel(new GridBagLayout());
    GridBagConstraints gbc = new GridBagConstraints();
    gbc.insets = new Insets(0,0,0,45);
    buttonPanel.add(upButton, gbc);
    buttonPanel.add(downButton, gbc);
    gbc.insets = new Insets(0,0,0,0);
    buttonPanel.add(unitButton, gbc);
    buttonPanel.add(blockButton, gbc);
    JPanel panel = new JPanel(new GridBagLayout());
    gbc.insets = new Insets(0,50,0,0);
    gbc.weightx = 1.0;
    gbc.weighty = 1.0;
    gbc.gridwidth = gbc.REMAINDER;
    gbc.anchor = gbc.WEST;
    for(int j = 0; j < 20; j++)
      panel.add(new JLabel(String.valueOf(j)), gbc);
    panel.setBackground(Color.yellow);
    panel.setPreferredSize(new Dimension(1000,1000));
    scrollPane = new JScrollPane(panel);
    scrollPane.getVerticalScrollBar().setUnitIncrement(50);
    scrollPane.getVerticalScrollBar().setBlockIncrement(200);
    getContentPane().add(scrollPane, "Center");
    getContentPane().add(buttonPanel, "South");
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setSize(400,300);
    setLocation(300,400);
    setVisible(true);
  public void actionPerformed(ActionEvent e) {
    JButton button = (JButton)e.getSource();
    int inc;
    if(button == upButton) {
      JScrollBar vertBar = scrollPane.getVerticalScrollBar();
      int currentValue = vertBar.getValue();
      if(unitButton.isSelected())
        inc = vertBar.getUnitIncrement(-1);
      else
        inc = vertBar.getBlockIncrement(-1);
      if(currentValue + inc < vertBar.getMaximum())
        vertBar.setValue(currentValue + inc);
      else
        vertBar.setValue(vertBar.getMinimum());
    if(button == downButton) {
      JScrollBar vertBar = scrollPane.getVerticalScrollBar();
      int currentValue = vertBar.getValue();
      if(unitButton.isSelected())
        inc = vertBar.getUnitIncrement(1);
      else
        inc = vertBar.getBlockIncrement(1);
      if(currentValue - inc > vertBar.getMinimum())
        vertBar.setValue(currentValue - inc);
      else
        vertBar.setValue(vertBar.getMinimum());
  public static void main(String[] args) {
    new souptier();
}