Develop Reference

Java : JTree and BasicTreeUI reference doesn't show scrollbars

Working with the JTreeWithScrollbar example, but scaled it back significantly to focus on the issue.
The original code would have the vertical scrollbars appear as needed.
Here, there is plenty of space and no scrollbars are needed.
If the panel is moved enough, the scrollbar will appear.
Once the following line of code was added, the scrollbars stopped appearing.
tree.setUI(new MyTreeUI());
Notice no scrollbar.
If the above line of code is commented out, the vertical scrollbar appears.
Checking the documentation for BasicTreeUI and there isn't anything related to showing/hiding scrollbars.
2 Questions
1 - When utilizing the BasicTreeUI object, what is required to ensure the scrollbars still function?
2 - Why is it the Horizontal scrollbar never appears even if the line of code is commented out?
import javax.swing.JEditorPane;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSplitPane;
import javax.swing.JTree;
import javax.swing.plaf.basic.BasicTreeUI;
import javax.swing.tree.DefaultMutableTreeNode;
import java.awt.Dimension;
public class JTreeWithScrollbar extends JPanel {
private JEditorPane htmlPane;
private JTree tree;
public JTreeWithScrollbar()
{
//Create the nodes.
DefaultMutableTreeNode top = new DefaultMutableTreeNode("The Java Series");
DefaultMutableTreeNode book1Node = new DefaultMutableTreeNode("Book 1");
DefaultMutableTreeNode book2Node = new DefaultMutableTreeNode("Book 2");
top.add(book1Node);
top.add(book2Node);
tree = new JTree(top);
tree.setUI(new MyTreeUI()); ///Comment out this line of code and the vertical scrollbar appears.
JScrollPane treeView = new JScrollPane(tree);
JScrollPane htmlView = new JScrollPane(htmlPane);
JSplitPane splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT);
splitPane.setTopComponent(treeView);
splitPane.setBottomComponent(htmlView);
Dimension minimumSize = new Dimension(100, 50);
htmlView.setMinimumSize(minimumSize);
splitPane.setDividerLocation(100);
splitPane.setPreferredSize(new Dimension(500, 300));
add(splitPane);
}
public static void main(String[] args)
{
//Create and set up the window.
JFrame frame = new JFrame("TreeDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel jp = new JPanel();
jp.add(new JTreeWithScrollbar());
frame.add(jp);
//Display the window.
frame.pack();
frame.setVisible(true);
}
private static class MyTreeUI extends BasicTreeUI
{
public MyTreeUI()
{
super();
}
#Override
protected void updateCachedPreferredSize() {
treeState.invalidateSizes();
tree.treeDidChange();
}
}
}

When utilizing the BasicTreeUI object, what is required to ensure the scrollbars still function?
As shown in the minimal example below, BasicTreeUI correctly shows each scroll bar when needed; resize the frame to see the effect.
Why does the horizontal scrollbar never appear even if the line of code is commented out?
After pack() the frame has been resized to adopt the preferred size of it content. Making the frame slightly smaller illustrates the effect. Your example adds the tree to a JPanel having a default FlowLayout which ignores preferred sizes; the example below adds the tree to the center of the frame's default BorderLayout which responds to preferred sizes.
I am assuming the updateCachedPreferredSize() must be doing other stuff behind the scenes…
Exactly. Each invocation of updateCachedPreferredSize() updates the component's preferred size to reflect any change in state (resize, expand, etc.); when the preferred size exceeds the viewport size, the scroll bars appear. As you observed, invoking super.updateCachedPreferredSize() allows normal operation, and any further customization must preserve that functionality.
In addition,
Expand rows as need like this.
Construct and manipulate Swing GUI objects only on the event dispatch thread.
Don't use setSize() when you really mean to override getPreferredSize() or illustrates a resize effect; more here.
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.plaf.basic.BasicTreeUI;
public class JTreeWithScrollbar {
public static void main(String[] args) {
EventQueue.invokeLater(() -> {
//Create and set up the window.
JFrame frame = new JFrame("TreeDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JTree tree = new JTree(); //default model
for (int i = 0; i < tree.getRowCount(); i++) {
tree.expandRow(i);
}
tree.setUI(new MyTreeUI());
frame.add(new JScrollPane(tree));
//Display the window.
frame.pack();
frame.setSize(frame.getWidth() - 10, frame.getHeight() - 100);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
});
}
private static class MyTreeUI extends BasicTreeUI {
}
}

Java swing JScrollPane not scrollable

This is the add(main) version
This is the add(scroll) version
Im trying to get a window full of lables and make it scrollable, this is my code for that purpose:
public class JobHistoryListScreen extends JFrame implements View
{
#Override
public void showScreen()
{
setSize(800, 800);
setLayout(new BorderLayout());
setDefaultCloseOperation(EXIT_ON_CLOSE);
JPanel main = new JPanel();
main.setSize(500,500);
JScrollPane scroll = new JScrollPane(main,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
scroll.setSize(500,500);
//Font
//Font david50 = new Font("David", Font.BOLD, 50);
for(int i=0; i<1000; i++)
{
JLabel empty = new JLabel("No jobs to display!");
empty.setBounds(0,i+250,400,100);
empty.setFont(david50);
main.add(empty);
}
add(main);
setVisible(true);
}
public static void main(String[] args) {
JobHistoryListScreen v = new JobHistoryListScreen();
v.showScreen();
}
}
For some reason the window gets filled with the labels but is not scrollable at all.

Learn about layout managers. Refer to Laying Out Components Within a Container. Default for JPanel is FlowLayout and because the JPanel is inside a JScrollPanel, the labels will not wrap. And since you set the horizontal scroll bar policy to NEVER, there is no horizontal scroll bar and hence you cannot scroll horizontally. Try using BoxLayout to display all the labels one under the other. Alternatively you could use a GridLayout with 0 (zero) rows and 1 (one) column. Refer to the tutorial for more details.
EDIT
Here is my modified version of your code. Explanatory notes appear after the code.
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.GridLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.WindowConstants;
public class JobHistoryListScreen implements Runnable {
private JFrame frame;
#Override // java.lang.Runnable
public void run() {
showScreen();
}
public void showScreen() {
frame = new JFrame("Jobs");
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
JPanel main = new JPanel(new GridLayout(0, 1));
JScrollPane scroll = new JScrollPane(main,
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
scroll.setPreferredSize(new Dimension(500, 500));
Font david50 = new Font("David", Font.BOLD, 50);
for(int i=0; i<1000; i++) {
JLabel empty = new JLabel("No jobs to display!");
empty.setFont(david50);
main.add(empty);
}
frame.add(scroll);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
JobHistoryListScreen v = new JobHistoryListScreen();
// Launch Event Dispatch Thread (EDT)
EventQueue.invokeLater(v);
}
}
I don't know what interface View is so I removed that part.
No need to extend class JFrame.
No need to explicitly call setSize() on JFrame. Better to call pack().
Default content pane for JFrame is JPanel and default layout manager for that JPanel is BorderLayout so no need to explicitly set.
No need to call setSize() on JPanel.
Call setPreferredSize() rather than setSize() on JScrollPane.
Add the JScrollPane to the JFrame and not the JPanel.
No need to call setBounds() because GridLayout handles this.
Explicitly launch EDT (Event Dispatch Thread) by calling invokeLater().
Here is a screen capture of the running app. Note the vertical scroll bar.

Java Swing Moving Away From Null Layout

I built a great GUI using the frowned upon null layout (I defined a lot of constants and used a window resize listener to make it easy). Everything worked perfectly until I started using a new computer. Now, the component's are not positioned properly (from the picture you can see that the components are offset down and right). After researching the problem I learned that layout managers make sure that the components are positioned properly throughout different machines. Because of this, I would like to start rebuilding the GUI in an actual layout manager. The problem is that I often feel limited in the way I position components when attempting to use an actual layout manager.
For anyone who is curious, I was originally using a dell inspiron laptop with windows 10, and have moved to an Asus Laptop (I don't know the actual model, but the touch screen can detach from the keyboard), also with windows 10.
My question:
Which layout manager would be the fastest and easiest to build the GUI shown in the picture above (out of the stock Swing Layouts and others). I would like this layout to respect the components' actual sizes for only a few but not all of the components. Using this layout, how would I go about positioning the inventory button (the hammer at the bottom left) so that the bottom left corner of the inventory button is 5 pixels up and right from the bottom left corner of the container, even after resizing the container?
Thanks in advance. All help is appreciated.
EDIT: The "go find a key" and "Attempt to force the door open" options should have their sizes respected.

The simplest solution that comes to my mind is a BorderLayout for the main panel. Add the textarea to NORTH / PAGE_START. Make another BorderLayout containing the inventory button (WEST / LINE_START) and the location label (EAST / LINE_END). Add that to SOUTH / PAGE_END of the main BorderLayout. Then just add a BoxLayout with vertical alignment to the main BorderLayout's CENTER containing the two buttons. Here's a tutorial for the standard layout managers.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Insets;
import java.awt.image.BufferedImage;
import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextArea;
public class Example {
public Example() {
JTextArea textArea = new JTextArea("There is a locked door");
textArea.setRows(5);
textArea.setBorder(BorderFactory.createLineBorder(Color.GRAY));
textArea.setEditable(false);
WhiteButton button1 = new WhiteButton("Go find a key") {
#Override
public Dimension getMinimumSize() {
return new Dimension(200, 25);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 25);
}
#Override
public Dimension getMaximumSize() {
return new Dimension(200, 25);
}
};
WhiteButton button2 = new WhiteButton("Attempt to force the door open");
button2.setMargin(new Insets(0, 60, 0, 60));
JPanel buttonPanel = new JPanel();
buttonPanel.setLayout(new BoxLayout(buttonPanel, BoxLayout.Y_AXIS));
buttonPanel.add(button1);
buttonPanel.add(Box.createVerticalStrut(5));
buttonPanel.add(button2);
WhiteButton inventoryButton = new WhiteButton(
new ImageIcon(new BufferedImage(50, 50, BufferedImage.TYPE_INT_RGB)));
JLabel locationLabel = new JLabel("Location: 0");
locationLabel.setVerticalAlignment(JLabel.BOTTOM);
JPanel southPanel = new JPanel(new BorderLayout());
southPanel.add(inventoryButton, BorderLayout.WEST);
southPanel.add(locationLabel, BorderLayout.EAST);
JPanel mainPanel = new JPanel(new BorderLayout(0, 5));
mainPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
mainPanel.add(textArea, BorderLayout.NORTH);
mainPanel.add(buttonPanel);
mainPanel.add(southPanel, BorderLayout.SOUTH);
JFrame frame = new JFrame("Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setContentPane(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new Example();
}
});
}
private class WhiteButton extends JButton {
public WhiteButton() {
setBackground(Color.WHITE);
}
public WhiteButton(String text) {
this();
setText(text);
}
public WhiteButton(ImageIcon icon) {
this();
setIcon(icon);
setBorder(BorderFactory.createLineBorder(Color.GRAY));
}
}
}

Java - Set size of decorated JFrame

I've got a problem with the size of a JFrame:
I want to show content in the Jframe. The content will have the size 640 x 480. But I can not use the method JFrame.setSize(640, 480); because I also want to show the decoration of the window.
My first thought was: Add a panel with the preferred dimension and than use pack();. But this also doesn't work - I only get a really small window.
I think the solution to my problem could be similar to this:
String JFrame Size
How do I make a JFrame a certain size not including the border
Here is my code:
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class Fenster extends JFrame {
JPanel panel;
Dimension dim;
Fenster(){
dim = new Dimension(640, 480);
panel = new JPanel();
panel.setSize(dim);
panel.setMinimumSize(dim);
panel.setMaximumSize(dim);
panel.setPreferredSize(dim);
panel.setBounds(0, 0, 640, 480);
panel.setDoubleBuffered(true);
JLabel label = new JLabel("bla");
panel.add(label);
this.setLayout(null);
this.getContentPane().add(panel);
this.setLocationRelativeTo(null);
this.setResizable(false);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
this.pack();
this.setVisible(true);
}
}

this.setLayout(null); is your problem. Let the layout manager do it's job
From the JavaDocs
public void pack() Causes this Window to be sized to fit the
preferred size and layouts of its subcomponents. The resulting width
and height of the window are automatically enlarged if either of
dimensions is less than the minimum size as specified by the previous
call to the setMinimumSize method. If the window and/or its
owner are not displayable yet, both of them are made displayable
before calculating the preferred size. The Window is validated after
its size is being calculated.
Most containers (JComponent, JPanel) have a default, preferred size of 0x0, the layout manager provides this information based on the requirements of the layout manager itself and the contents of the container, but using a null, you effectivly make the container 0x0...
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setUndecorated(true);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
public TestPane() {
setLayout(new GridBagLayout());
add(new JLabel("Look ma, no null layouts!"));
}
#Override
public Dimension getPreferredSize() {
return new Dimension(640, 480);
}
}
}
Avoid using null layouts, pixel perfect layouts are an illusion within modern ui design. There are too many factors which affect the individual size of components, none of which you can control. Swing was designed to work with layout managers at the core, discarding these will lead to no end of issues and problems that you will spend more and more time trying to rectify
See Why is it frowned upon to use a null layout in SWING? for more details...

JLabel alignment in JPanel

I'm trying to align a JLabel to the right in a JPanel. I'm adding a JTabbedPane, a JPanel which contains my JLabel and JTextArea to a main JPanel.
I have searched SO and tried some methods like setAlignmentX, setHorizontalAlignment(SwingConstants.LEFT) and nested containers to no avail.
Here's my code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class LabelProblem
{
public static void main(String[] args)
{
JFrame frame = new JFrame("Label Problem");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel Main = new JPanel();
Main.setLayout(new BoxLayout(Main, BoxLayout.Y_AXIS));
JPanel ComponentPanel = new JPanel();
JLabel label = new JLabel("Sample Text");
label.setHorizontalAlignment(SwingConstants.LEFT);
label.setBorder(BorderFactory.createLineBorder(Color.BLACK));
label.setAlignmentX(Component.RIGHT_ALIGNMENT);
ComponentPanel.add(label);
JTabbedPane Tab = new JTabbedPane();
Tab.add("Document 1", new JPanel());
Main.add(Tab);
Main.add(ComponentPanel);
JTextArea Area = new JTextArea(10,10);
JScrollPane Scroll = new JScrollPane(Area);
frame.add(Main);
frame.add(Scroll, BorderLayout.SOUTH);
frame.setSize(450,450);
frame.setVisible(true);
}
}
How can I align my JLabel to the right?
Thanks!

So, the place of that label is determined by the layout of ComponentPanel. Since you didn't specify any layout it is using the default FlowLayout with a CENTER alignment. Assuming that you are ok with a FlowLayout it is a mere question of setting the alignment of the LEFT since this is possible with this layout.
Here's the code with the fix, however I suspect that as you put more elements to the ComponentPanel you will want to use another layout since FlowLayout is more adequate for menus and the like and not for displaying the main content.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.FlowLayout;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTabbedPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
class LabelProblem
{
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
initGUI();
}
});
}
public static void initGUI()
{
JFrame frame = new JFrame("Label Problem");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel main = new JPanel();
main.setLayout(new BoxLayout(main, BoxLayout.Y_AXIS));
JPanel componentPanel = new JPanel(new FlowLayout(FlowLayout.LEFT));
JLabel label = new JLabel("Sample Text");
label.setBorder(BorderFactory.createLineBorder(Color.BLACK));
componentPanel.add(label);
JTabbedPane Tab = new JTabbedPane();
Tab.add("Document 1", new JPanel());
main.add(Tab);
main.add(componentPanel);
JTextArea area = new JTextArea(10, 10);
JScrollPane scroll = new JScrollPane(area);
frame.add(main);
frame.add(scroll, BorderLayout.SOUTH);
frame.setSize(450, 450);
frame.setVisible(true);
}
}
Result:
Note: I also changed the variable names to follow the java style convention: variable names should start with lower case to differenciate them from clases names, starting in upper case.

One simple approach is to set the label's horizontalAlignment to JLabel.RIGHT in the constructor.
import java.awt.*;
import javax.swing.*;
class LabelProblem {
public static void main(String[] args) {
JFrame frame = new JFrame("Label Problem");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new GridLayout(0, 1));
JTabbedPane tab = new JTabbedPane();
tab.add("Document 1", new JPanel());
frame.add(tab);
JLabel label = new JLabel("Sample Text", JLabel.RIGHT);
frame.add(label);
JTextArea area = new JTextArea(10, 10);
JScrollPane scroll = new JScrollPane(area);
frame.add(scroll);
frame.pack();
frame.setSize(450, 450);
frame.setVisible(true);
}
}

I think it may be a matter of you not actually setting layouts where you imagine you're setting layouts.
You have a JPanel with a vertically oriented BoxLayout (Main) enclosing another JPanel with default layout (ComponentPanel), finally enclosing your label. The reason why your label can't be pushed to the right is because is already is pushed to the right within it's enclosing container. If you set a colored border around ComponentPanel, you'll see what I mean -- it only occupies the same amount of space as the JLabel, giving the JLabel nowhere to move.
You need to set a layout and constraints for your intermediate ComponentPanel, allowing it to horizontally fill its parent container so that the label has someplace to go.
You haven't really specified how your layout is supposed to look, but if you change the layout on Main to X_AXIS, your label will pop over to the left (as will its parent container). Without knowing what you're really trying to do, I can't say much more.
I would however, suggest you throw your BoxLayout away entirely and look into using GridBagLayout, which gives you a high level control over your UI. GridBagLayout isn't the most concise construct, but that's the price of control.