I'm trying to create a GUI in swing. The GUI would hold a variable number of JPanels of a fixed height stacked on top of one another. When the total height of the JPanels in the stack is greater than the height of enclosing frame, the user should be able to scroll up and down through the Panels.
____________________
| |
| panel 1 |
| |
|____________________|
| |
| panel 2 |
| |
|____________________|
___|____________________|___
| | panel 3 | |
| | | |
| |____________________| | ^
| | | | |
| | panel 4 | | |
| | | | |
| |____________________| | v
| | | |
| | panel 5 | |
|___|____________________|___|
|____________________|
| |
| panel 6 |
| |
|____________________|
I've tried using a combination of JScrollPanes and JPanels with GridLayout and GridBagLayout as well as calls to setPreferedSize and setMinimumSize to no success. I feel that setting this sort of gui up should be fairly straightforward but can't seem to figure out a solution.
If you use JPanels, then the JPanel that is held by the viewport should override the JPanel class and should implement the Scrollable interface, returning proper values for the overridden methods, especially the getPreferredScrollableViewportSize() method. For my money though, I'd prefer to use a JList and use appropriate renderers instead of JPanels, and then setting my JLists visibleRowCount via its setVisibleRowCount(...) method.
For example:
Example edited to now show both JList and a Scrollable JPanel
import java.awt.Component;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Insets;
import java.awt.Rectangle;
import javax.swing.*;
@SuppressWarnings("serial")
public class VisibleRows extends JPanel {
private DefaultListModel<Datum> dataModel = new DefaultListModel<>();
private JList<Datum> datumList = new JList<>(dataModel);
public VisibleRows() {
DataPanel dataPanel = new DataPanel(8);
for (int i = 0; i < 200; i++) {
String name = "John Smith " + i;
int value = i;
Datum datum = new Datum(name, value);
dataPanel.addDatum(datum);
dataModel.addElement(datum);
}
JScrollPane scrollPane1 = new JScrollPane(dataPanel);
scrollPane1.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
add(scrollPane1);
datumList.setVisibleRowCount(8);
datumList.setCellRenderer(new DatumRenderer());
datumList.setPrototypeCellValue(new Datum("XXXXXXXXXXX", 200));
JScrollPane scrollPane2 = new JScrollPane(datumList);
scrollPane2.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
add(scrollPane2);
}
private static void createAndShowGui() {
JFrame frame = new JFrame("VisibleRows");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new VisibleRows());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
@SuppressWarnings("serial")
class DatumRenderer extends DatumPanel implements ListCellRenderer<Datum> {
@Override
public Component getListCellRendererComponent(JList<? extends Datum> list, Datum value, int index,
boolean isSelected, boolean cellHasFocus) {
setDatum(value);
return this;
}
}
@SuppressWarnings("serial")
class DataPanel extends JPanel implements Scrollable {
private int visibleRowCount = 1;
public DataPanel(int visibleRowCount) {
this.visibleRowCount = visibleRowCount;
setLayout(new GridLayout(0, 1));
}
public void addDatum(Datum datum) {
add(new DatumPanel(datum));
}
@Override
public Dimension getPreferredScrollableViewportSize() {
if (getComponentCount() > 0) {
JComponent comp = (JComponent) getComponents()[0];
int width = getPreferredSize().width;
int height = visibleRowCount * comp.getPreferredSize().height;
Dimension d = new Dimension(width, height);
System.out.println(d);
return d;
} else {
return new Dimension(0, 0);
}
}
@Override
public int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction) {
if (getComponentCount() > 0) {
JComponent comp = (JComponent) getComponents()[0];
Dimension d = comp.getPreferredSize();
if (orientation == SwingConstants.VERTICAL) {
return d.height;
} else {
return d.width;
}
}
return 0;
}
@Override
public int getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction) {
if (getComponentCount() > 0) {
JComponent comp = (JComponent) getComponents()[0];
Dimension d = comp.getPreferredSize();
if (orientation == SwingConstants.VERTICAL) {
return visibleRowCount * d.height;
} else {
return d.width;
}
}
return 0;
}
@Override
public boolean getScrollableTracksViewportWidth() {
return true;
}
@Override
public boolean getScrollableTracksViewportHeight() {
return false;
}
}
@SuppressWarnings("serial")
class DatumPanel extends JPanel {
private static final int GBC_I = 3;
private Datum datum;
private JLabel nameLabel = new JLabel();
private JLabel valueLabel = new JLabel();
public DatumPanel() {
setLayout(new GridBagLayout());
add(new JLabel("Name:"), createGbc(0, 0));
add(nameLabel, createGbc(1, 0));
add(new JLabel("Value:"), createGbc(0, 1));
add(valueLabel, createGbc(1, 1));
}
public DatumPanel(Datum datum) {
this();
setDatum(datum);
}
public final void setDatum(Datum datum) {
this.datum = datum;
nameLabel.setText(datum.getName());
valueLabel.setText("" + datum.getValue());
}
public Datum getDatum() {
return datum;
}
private GridBagConstraints createGbc(int x, int y) {
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = x;
gbc.gridy = y;
gbc.insets = new Insets(GBC_I, GBC_I, GBC_I, GBC_I);
gbc.insets.left = x != 0 ? 3 * GBC_I : GBC_I;
gbc.weightx = 0.0;
gbc.weighty = 0.0;
return gbc;
}
}
class Datum {
private String name;
private int value;
public Datum(String name, int value) {
this.name = name;
this.value = value;
}
public String getName() {
return name;
}
public int getValue() {
return value;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("Name: " + name + "\n");
sb.append("Value: " + value);
return super.toString();
}
}