Adding vertical scroll to a JPopupMenu?
I would like to add a way to scroll through menu items in a JPopupMenu, much like scrolling through a list of items in a JComboBox.
Let's say I have 10 menu items. I would like to display only 5 menu items at a time, and I would use a vertical scroll button at the bottom or top of the JPopupMenu to show the menu items that are not listed and hide the ones that I just saw.
Is it possible? I am using JIDE Software's JideSplitButton, which displays a JPopupMenu when clicked. I am trying to keep the look and feel of the command bar on which I placed the JideSplitButton, so I don't want to replace it with a JComboBox unless I really have to.
Answer
Here is a version I created using a scrollbar. It is just a simple example, so adapt as you see fit:
import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Insets;
import java.awt.LayoutManager;
import java.awt.event.AdjustmentEvent;
import java.awt.event.AdjustmentListener;
import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;
import javax.swing.JPopupMenu;
import javax.swing.JScrollBar;
public class JScrollPopupMenu extends JPopupMenu {
protected int maximumVisibleRows = 10;
public JScrollPopupMenu() {
this(null);
}
public JScrollPopupMenu(String label) {
super(label);
setLayout(new ScrollPopupMenuLayout());
super.add(getScrollBar());
addMouseWheelListener(new MouseWheelListener() {
@Override public void mouseWheelMoved(MouseWheelEvent event) {
JScrollBar scrollBar = getScrollBar();
int amount = (event.getScrollType() == MouseWheelEvent.WHEEL_UNIT_SCROLL)
? event.getUnitsToScroll() * scrollBar.getUnitIncrement()
: (event.getWheelRotation() < 0 ? -1 : 1) * scrollBar.getBlockIncrement();
scrollBar.setValue(scrollBar.getValue() + amount);
event.consume();
}
});
}
private JScrollBar popupScrollBar;
protected JScrollBar getScrollBar() {
if(popupScrollBar == null) {
popupScrollBar = new JScrollBar(JScrollBar.VERTICAL);
popupScrollBar.addAdjustmentListener(new AdjustmentListener() {
@Override public void adjustmentValueChanged(AdjustmentEvent e) {
doLayout();
repaint();
}
});
popupScrollBar.setVisible(false);
}
return popupScrollBar;
}
public int getMaximumVisibleRows() {
return maximumVisibleRows;
}
public void setMaximumVisibleRows(int maximumVisibleRows) {
this.maximumVisibleRows = maximumVisibleRows;
}
public void paintChildren(Graphics g){
Insets insets = getInsets();
g.clipRect(insets.left, insets.top, getWidth(), getHeight() - insets.top - insets.bottom);
super.paintChildren(g);
}
protected void addImpl(Component comp, Object constraints, int index) {
super.addImpl(comp, constraints, index);
if(maximumVisibleRows < getComponentCount()-1) {
getScrollBar().setVisible(true);
}
}
public void remove(int index) {
// can't remove the scrollbar
++index;
super.remove(index);
if(maximumVisibleRows >= getComponentCount()-1) {
getScrollBar().setVisible(false);
}
}
public void show(Component invoker, int x, int y){
JScrollBar scrollBar = getScrollBar();
if(scrollBar.isVisible()){
int extent = 0;
int max = 0;
int i = 0;
int unit = -1;
int width = 0;
for(Component comp : getComponents()) {
if(!(comp instanceof JScrollBar)) {
Dimension preferredSize = comp.getPreferredSize();
width = Math.max(width, preferredSize.width);
if(unit < 0){
unit = preferredSize.height;
}
if(i++ < maximumVisibleRows) {
extent += preferredSize.height;
}
max += preferredSize.height;
}
}
Insets insets = getInsets();
int widthMargin = insets.left + insets.right;
int heightMargin = insets.top + insets.bottom;
scrollBar.setUnitIncrement(unit);
scrollBar.setBlockIncrement(extent);
scrollBar.setValues(0, heightMargin + extent, 0, heightMargin + max);
width += scrollBar.getPreferredSize().width + widthMargin;
int height = heightMargin + extent;
setPopupSize(new Dimension(width, height));
}
super.show(invoker, x, y);
}
protected static class ScrollPopupMenuLayout implements LayoutManager{
@Override public void addLayoutComponent(String name, Component comp) {}
@Override public void removeLayoutComponent(Component comp) {}
@Override public Dimension preferredLayoutSize(Container parent) {
int visibleAmount = Integer.MAX_VALUE;
Dimension dim = new Dimension();
for(Component comp :parent.getComponents()){
if(comp.isVisible()) {
if(comp instanceof JScrollBar){
JScrollBar scrollBar = (JScrollBar) comp;
visibleAmount = scrollBar.getVisibleAmount();
}
else {
Dimension pref = comp.getPreferredSize();
dim.width = Math.max(dim.width, pref.width);
dim.height += pref.height;
}
}
}
Insets insets = parent.getInsets();
dim.height = Math.min(dim.height + insets.top + insets.bottom, visibleAmount);
return dim;
}
@Override public Dimension minimumLayoutSize(Container parent) {
int visibleAmount = Integer.MAX_VALUE;
Dimension dim = new Dimension();
for(Component comp : parent.getComponents()) {
if(comp.isVisible()){
if(comp instanceof JScrollBar) {
JScrollBar scrollBar = (JScrollBar) comp;
visibleAmount = scrollBar.getVisibleAmount();
}
else {
Dimension min = comp.getMinimumSize();
dim.width = Math.max(dim.width, min.width);
dim.height += min.height;
}
}
}
Insets insets = parent.getInsets();
dim.height = Math.min(dim.height + insets.top + insets.bottom, visibleAmount);
return dim;
}
@Override public void layoutContainer(Container parent) {
Insets insets = parent.getInsets();
int width = parent.getWidth() - insets.left - insets.right;
int height = parent.getHeight() - insets.top - insets.bottom;
int x = insets.left;
int y = insets.top;
int position = 0;
for(Component comp : parent.getComponents()) {
if((comp instanceof JScrollBar) && comp.isVisible()) {
JScrollBar scrollBar = (JScrollBar) comp;
Dimension dim = scrollBar.getPreferredSize();
scrollBar.setBounds(x + width-dim.width, y, dim.width, height);
width -= dim.width;
position = scrollBar.getValue();
}
}
y -= position;
for(Component comp : parent.getComponents()) {
if(!(comp instanceof JScrollBar) && comp.isVisible()) {
Dimension pref = comp.getPreferredSize();
comp.setBounds(x, y, width, pref.height);
y += pref.height;
}
}
}
}
}