Develop Reference

How to make a Jframe containing a Jpanel scrollable?

So I have this JFrame that contains a JPanel and in there I add JLabels with information I want but since I'll be adding labels all the time at some point the text is too long to appear so I want to add a scrollbar. Basically I want to make my JFrame with a JPanel in it scrollable. I have this code but my problem is that even though the scrollbar appears but it doesnt move and doesn't really work when the text is a lot, meaning the text still gets cut out and the scrollbar is there not moving. Does anyone know how to fix this?
import javax.swing.*;
import java.awt.*;
import java.util.*;
public class Bar {
JFrame info = new JFrame("Information");
JLabel ballinf = new JLabel();
JPanel contentPane = new JPanel();
JScrollPane scrolling = new JScrollPane();
public Bar(){
contentPane.setOpaque(true);
contentPane.setBackground(Color.WHITE);
contentPane.setLayout(null);
scrolling = new JScrollPane(contentPane,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
info.add(scrolling);
info.setSize(750, 600);
info.setLocationByPlatform(true);
info.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
info.setVisible(true);
}
public void adding(int pos){
ballinf = new JLabel("Something ",JLabel.CENTER);//assume the text will be bigger here and have more info
ballinf.setSize(700, 30);
ballinf.setForeground(Color.green);
ballinf.setLocation(5, 5+pos);
contentPane.add(ballinf);
info.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
info.setVisible(true);
}
public static void main(String[] args){
Bar stats = new Bar();
stats.adding(0);
stats.adding(20);//this will be done in a for loop for more than 2 times so the text ends up to be a lot
}
}

contentPane.setLayout(null);
Don't use a null layout!!!
You need to use an appropriate layout manager. Read the section from the Swing tutorial on Layout Managers for more information and working examples. The layout manager will then determine the preferred size of the panel as you add components to the panel.
The scrollpane will then display the scrollbars when necessary.
If you dynamically add components to the panel (after the GUI is visible) then the code should be something like:
panel.add(...);
panel.revalidate();
panel.repaint();

Java JTextField window size

Im trying to display to the user some text:
JTextField warningComponent = new JTextField(VERY_LONG_TEXT_NOENTERS);
warningComponent.setEditable(false);
but the window size is changed according to the text size. I want to set the window to be 30 X 40 all the time regardless of the warning text length.
And i want the warning text to be adjusted to the window size (maybe the user will have to scroll to see the end)
How do i do it?
Maybe i should use other swing component?
I tried most of the methods in JTextField class.
Thanks.

I add it to JPanel
Then the default layout manager should be a FlowLayout which will respect the preferred size of the text field.
To give a suggestion for the preferred size of the text field you need to do:
JTextField warningComponent = new JTextField(VERY_LONG_TEXT_NOENTERS, 20);
The second parameter will give a suggestion on how to size the text field to make approximately 20 characters visible at one time. You will then need to use the arrow keys to see the remaining characters.

And i want the warning text to be adjusted to the window size
If you want the textfield to resize according to the frame size and not the frame size following the dimension of the textfield, you may make use of specific layout to achieve that:
Using BorderLayout:
class MainPanel extends JPanel{
private JTextField txt;
public MainPanel(){
setLayout(new BorderLayout());
setPreferredSize(new Dimension(30, 40));
txt = new JTextField();
txt.setHorizontalAlignment(JTextField.HORIZONTAL);
add(txt);
}
}
Runner class to run to codes:
class TextFieldRunner{
public static void main(String[] args){
SwingUtilities.invokeLater(new Runnable(){
#Override
public void run(){
JFrame frame = new JFrame("Text Runner");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new MainPanel());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
}

You can try JScrollPane in your application, JScrollPane is scroll-able horizontally and vertically as you wish. And add JTextArea to JScrollPane. JTextField is not scroll-able.
Here is a small example:
JScrollPane scrollPane = new JScrollPane();
JTextArea textArea = new JTextArea();
scrollPane.add(textArea);
scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
This is the values for the scroll policy:
VERTICAL_SCROLLBAR_AS_NEEDED
VERTICAL_SCROLLBAR_NEVER
VERTICAL_SCROLLBAR_ALWAYS
HORIZONTAL_SCROLLBAR_AS_NEEDED
HORIZONTAL_SCROLLBAR_NEVER
HORIZONTAL_SCROLLBAR_ALWAYS

JTextArea with JScrollPAne within Frame with null Layout

I'm trying to add this JTextArea with a JScrollPane (with vertical but not horizontal scrollbar) to my frame but the result is just a grey area with a scrollbar on the right... I'm probably doing something really dumb but i've done that same exact thing to a JPanel and it worked
public class Chats {
public static int height = 600;
public static int length = 400;
public static void init(String me, String you){
JFrame frame = new JFrame ("Chat");
frame.setSize(larguraframe, alturaframe);
frame.setLocation(620, 100);
frame.setResizable(false);
frame.setLayout(null);
frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
JTextArea chat = new JTextArea();
chat.setColumns(10);
chat.setLineWrap(true);
chat.setWrapStyleWord(true);
JScrollPane scrollpane = new JScrollPane(chat, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER;
scrollpane.setBounds(length/8 - 27, height/9 + 27, 350, 380);
chat.setPreferredSize(new Dimension(lenght-15, 7*height/8-27));
frame.add(chat);
frame.add(scrollpane);
frame.setVisible(true);
}
}
I don't mind changing my frame's Layout but i really want one that allows me to put stuff exactly where i want it. Thanks
EDIT
Okay it now shows on my frame but the TextArea is still not resizable. When i write something in it using a JTextfield and a JButton with a Listener that appends the JTextfield's text to the JTextArea and then sets the text in the JTextField to "" it only accepts up to a certain ammount of lines. After that it just looks the same.

I know that you've already "accepted" an answer, but I feel that I'd be remiss if I didn't give an answer that gave important points, ones that in the long run would allow you to create a better and more robust (i.e., a more easily debuggable, modifiable, and enhanceable) application.
Again,
Never set a JTextArea's preferredSize, as this will create a JTextArea whose size is inflexibly set that will not add additional lines when needed. Instead set the JTextArea's row and column properties.
While null layouts and setBounds() might seem to Swing newbies like the easiest and best way to create complex GUI's, the more Swing GUI'S you create the more serious difficulties you will run into when using them. They won't resize your components when the GUI resizes, they are a royal witch to enhance or maintain, they fail completely when placed in scrollpanes, they look gawd-awful when viewed on all platforms or screen resolutions that are different from the original one.
Better to use a JPanel, or more often multiple nested JPanels, each using its own layout manager that allow you to more simply create agile and powerful complex yet beautiful GUI's.
When using layout managers, you'll want to pack() your JFrame after adding all components so that all layout managers will do their jobs and layout components appropriately.
I've an example program below I show,
a title JLabel with large centered text
a JTextArea, called chatViewArea, of specified row and column size held within a JScrollPane and that is for viewing the chat. It is non-focusable so that the user cannot directly interact with it.
Another JTextArea, called textEntryArea, for entering text. You could use a simple JTextField for this and give it an ActionListener so that it responds to the enter key, however if you want a multi-lined text component that acts similar, you'll need to change the key bindings for the JTextArea's enter key. I've done that here so that the enter key "submits" the text held within the textEntryArea JTextArea, and the control-enter key combination acts the same as the enter key used to -- creating a new line.
The main JPanel uses simply a BorderLayout to allow placement of the title at the top, the chat view JTextArea in the center and the text entry JTextArea at the bottom. Note that if you needed to see more components, such as a JList showing other chatters, this can be done by nesting JPanels and using more layouts if need be.
For example:
import java.awt.BorderLayout;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.*;
#SuppressWarnings("serial")
public class Chat2 extends JPanel {
private static final int ROWS = 25; // rows in the chat view JTextArea
private static final int COLS = 40; // columns in the chat view JTextArea
// and text entry area
private static final int ENTRY_ROWS = 4; // rows in the text entry JTextArea
private static final int BL_HGAP = 10; // horizontal gap for our
// BorderLayout
private static final int BL_VGAP = 5; // vertical gap for our BorderLayout
private static final int EB_GAP = 15; // gap for empty border that goes
// around entire app
private static final String TITLE_TEXT = "My Chat Application";
private static final float TITLE_POINTS = 32f; // size of the title jlabel
// text
private JTextArea chatViewArea = new JTextArea(ROWS, COLS);
private JTextArea textEntryArea = new JTextArea(ENTRY_ROWS, COLS);
public Chat2() {
// label to display the title in bold large text
JLabel titleLabel = new JLabel(TITLE_TEXT, SwingConstants.CENTER);
titleLabel.setFont(titleLabel.getFont().deriveFont(Font.BOLD, TITLE_POINTS));
// set up the chat view JTextArea to have word wrap
// and to not be focusable
chatViewArea.setWrapStyleWord(true);
chatViewArea.setLineWrap(true);
chatViewArea.setFocusable(false);
// add it to a JScrollPane, and give the scrollpane vertical scrollbars
JScrollPane viewScrollPane = new JScrollPane(chatViewArea);
viewScrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
// set up the text entry JTextArea
textEntryArea.setWrapStyleWord(true);
textEntryArea.setLineWrap(true);
// key bindings so that control-enter will act as enter and the enter key will "submit"
// the user input to the chat window and the chat server
// will allow us to use a multilined text entry area if desired instead
// of a single lined JTextField
setEnterKeyBinding(textEntryArea);
JScrollPane entryScrollPane = new JScrollPane(textEntryArea);
entryScrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
// add an empty border around entire application
setBorder(BorderFactory.createEmptyBorder(EB_GAP, EB_GAP, EB_GAP, EB_GAP));
// make the main layout a BorderLayout
setLayout(new BorderLayout(BL_HGAP, BL_VGAP));
// add our components to the GUI
add(titleLabel, BorderLayout.PAGE_START);
add(viewScrollPane, BorderLayout.CENTER);
add(entryScrollPane, BorderLayout.PAGE_END);
}
// Again, use key bindings so that control-enter JTextArea will act as enter key
// and the enter key will "submit" the user input to the chat window and the chat server.
// When ctrl-enter is pushed the Action originally bound to the enter key will be called
// and when enter is pushed a new Action, the EnterKeyAction, will be called
private void setEnterKeyBinding(JTextArea textArea) {
int condition = JComponent.WHEN_FOCUSED; // only for focused entry key
InputMap inputMap = textArea.getInputMap(condition);
ActionMap actionMap = textArea.getActionMap();
KeyStroke entryKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0);
KeyStroke ctrlEntryKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, KeyEvent.CTRL_DOWN_MASK);
// first give ctrl-enter the action held by enter
Object entryKey = inputMap.get(entryKeyStroke);
Action entryAction = actionMap.get(entryKey);
inputMap.put(ctrlEntryKeyStroke, ctrlEntryKeyStroke.toString());
actionMap.put(ctrlEntryKeyStroke.toString(), entryAction);
// now give enter key a new Action
EnterKeyAction enterKeyAction = new EnterKeyAction();
inputMap.put(entryKeyStroke, entryKeyStroke.toString());
actionMap.put(entryKeyStroke.toString(), enterKeyAction);
}
public void appendToChatArea(final String text) {
if (SwingUtilities.isEventDispatchThread()) {
chatViewArea.append(text + "\n");
} else {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
chatViewArea.append(text + "\n");
}
});
}
}
private class EnterKeyAction extends AbstractAction {
#Override
public void actionPerformed(ActionEvent e) {
String text = textEntryArea.getText();
textEntryArea.setText("");
chatViewArea.append("User: " + text + "\n");
// TODO send text to the chat server!
}
}
private static void createAndShowGui() {
Chat2 mainPanel = new Chat2();
JFrame frame = new JFrame("My Chat Window");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
// pack the JFrame so that it will size itself to its components
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}

Try setting a layout like this:
frame.setLayout(new BorderLayout());
And adding the scrollpane to the center:
frame.add(scrollpane, BorderLayout.CENTER);
Also remove the line pointed by Jire in his answer.

You don't need to add chat because it is adapted by scrollPane.
Remove this line: frame.add(chat);

Add
chat.setBounds(length/8 - 27, height/9 + 27, 330, 360);
And see the magic happen... but do tweek the arguments here in order to get the right dimensions.
For resizable frame just do frame.setResizable(true); instead of frame.setResizable(false);

How to remove the padding between in the JPanel still using a flow layout?

Here's the portion of my java application GUI that I have a question about.
What this GUI consists is a blue JPanel(container) with default FlowLayout as LayoutManager that contains a Box which contains two JPanels(to remove the horizontal spacing or i could have used setHgaps to zero for that matter instead of a Box) that each contains a JLabel.
Here's my code for creating that part of the GUI.
private void setupSouth() {
final JPanel southPanel = new JPanel();
southPanel.setBackground(Color.BLUE);
final JPanel innerPanel1 = new JPanel();
innerPanel1.setBackground(Color.ORANGE);
innerPanel1.setPreferredSize(new Dimension(DEFAULT_WIDTH, DEFAULT_HEIGHT));
innerPanel1.add(new JLabel("Good"));
final JPanel innerPanel2 = new JPanel();
innerPanel2.setBackground(Color.RED);
innerPanel2.setPreferredSize(new Dimension(DEFAULT_WIDTH, DEFAULT_HEIGHT));
innerPanel2.add(new JLabel("Luck!"));
final Box southBox = new Box(BoxLayout.LINE_AXIS);
southBox.add(innerPanel1);
southBox.add(innerPanel2);
myFrame.add(southPanel, BorderLayout.SOUTH);
}
My question is how would i get rid the vertical padding between the outer JPanel(the blue one) and the Box?
I know this is padding because i read on Difference between margin and padding? that "padding = space around (inside) the element from text to border."
This wouldn't work because this has to due with gaps(space) between components.- How to remove JPanel padding in MigLayout?
I tried this but it didn't work either. JPanel Padding in Java

You can just set the gaps in the FlowLayout, i.e.
FlowLayout layout = (FlowLayout)southPanel.getLayout();
layout.setVgap(0);
The default FlowLayout has a 5-unit horizontal and vertical gap. Horizontal doesn't matter in this case as the BorderLayout is stretching the panel horizontally.
Or simple initialize the panel with a new FlowLayout. It'll be the same result.
new JPanel(new FlowLayout(FlowLayout.CENTER, 0, 0));
Edit:
"I tried that, didn't work.."
Works for me...
Setting the gap ↑ Not setting the gap ↑
import java.awt.*;
import javax.swing.*;
public class Test {
public void init() {
final JPanel southPanel = new JPanel();
FlowLayout layout = (FlowLayout)southPanel.getLayout();
layout.setVgap(0);
southPanel.setBackground(Color.BLUE);
final JPanel innerPanel1 = new JPanel();
innerPanel1.setBackground(Color.ORANGE);
innerPanel1.add(new JLabel("Good"));
final JPanel innerPanel2 = new JPanel();
innerPanel2.setBackground(Color.RED);
innerPanel2.add(new JLabel("Luck!"));
final Box southBox = new Box(BoxLayout.LINE_AXIS);
southBox.add(innerPanel1);
southBox.add(innerPanel2);
southPanel.add(southBox); // <=== You're also missing this
JFrame myFrame = new JFrame();
JPanel center = new JPanel();
center.setBackground(Color.yellow);
myFrame.add(center);
myFrame.add(southPanel, BorderLayout.SOUTH);
myFrame.setSize(150, 100);
myFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
myFrame.setLocationByPlatform(true);
myFrame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable(){
public void run() {
new Test().init();
}
});
}
}
Note: Always post a runnable example (as I have done) for better help. You say it doesn't work, but it always works for me, so how would we know what you're doing wrong without some code that will run and demonstrate the problem?

How do I resize JScrollPane after resizing a JTextArea

My JFrame Consists of three main parts a banner at top scrollpane containing a JTextArea center and a JTextField at the bottom. When I re-size the frame I adjust the columns and rows in my JTextArea. When making the frame larger the JTextArea expands visually but removes the scroll-bar. Then if I make the frame smaller the JTextArea stays the same size. This Is where I attempt to re-size my JTextArea.
frame.addComponentListener(new ComponentAdapter() {//Waits for window to be resized by user
public void componentResized(ComponentEvent e) {
uneditTextArea.setRows(((int)((frame.getHeight()-140)/18.8)));//sets Textarea size based on window size
uneditTextArea.setColumns(((int)((frame.getWidth()-100)/10.8)));
frame.revalidate();//refreshes screen
}
});
Why would the ScrollPane not re adjust to the change in size of the TextField.
The Rest of the code is below in case it is needed.
public class window extends JFrame
{
private static JFrame frame = new JFrame("Lillian");
private static JButton inputButton = new JButton("Send");
private static JTextField editTextArea = new JTextField(46);
private static JTextArea uneditTextArea = new JTextArea(26,50);
private static JPanel logoPanel = new JPanel();//Input text window
private static JPanel itextPanel = new JPanel();//Input text window
private static JPanel submitPanel = new JPanel();//Submit Button
private static JPanel bottom = new JPanel();//will contain scrollpane
private static JPanel middle = new JPanel();//willcontain itextpanel & submitbutton
private static JPanel otextPanel = new JPanel();//Text Output
public static void runWindow()
{
ImageIcon logo = new ImageIcon("Lillian_resize.png");//banner
ImageIcon icon = new ImageIcon("Lillian_icon.png");//application icon
frame.setIconImage(icon.getImage());
frame.setSize(660,640);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
logoPanel.setSize(10,10);
JLabel logoLabel = new JLabel(logo);
final JScrollPane scrollPane = new JScrollPane(otextPanel);//adds text to panel will scrollbar
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);//scrollbar only apears when more text than screen
scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);//scrollbar never apears
scrollPane.setBorder(BorderFactory.createEmptyBorder());
logoPanel.add(logoLabel);
submitPanel.add(inputButton);
itextPanel.add(editTextArea);
otextPanel.add(uneditTextArea);
frame.getContentPane().add(logoPanel,"North");
frame.getContentPane().add(middle);
frame.getContentPane().add(bottom,"South");
middle.add(scrollPane,"North");//adds panels to outer panel
bottom.add(itextPanel, "West");
bottom.add(submitPanel, "East");
uneditTextArea.setLineWrap(true);
uneditTextArea.setWrapStyleWord(true);
uneditTextArea.setEditable(false);
uneditTextArea.setCaretPosition(uneditTextArea.getDocument().getLength());
frame.revalidate();//refreshes screen
//---------------wait for action------------
frame.addComponentListener(new ComponentAdapter() {//Waits for window to be resized by user
public void componentResized(ComponentEvent e) {
uneditTextArea.setRows(((int)((frame.getHeight()-140)/18.8)));//sets Textarea size based on window size
uneditTextArea.setColumns(((int)((frame.getWidth()-100)/10.8)));
frame.revalidate();//refreshes screen
}
});
}
}

There should be no need to use a ComponentListener to resize components. That is the job of the layout managers that you use to dynamically resize the components.
You should not be adding the text area to a JPanel first. Instead when using text areas you would generally add the text area directly to the viewport of a JScrollPane by using code like:
JScrollPane scrollPane = new JScrollPane( textArea );
Then you add the scrollpane to the frame with code like:
frame.add(scrollPane, BorderLayout.CENTER);
As you have noticed you should also NOT use hardcoded literals like "Center". Instead use the variables provided by the layout manager. Since you are using a BorderLayout, use the variables defined in the BorderLayout class.
Also, you should NOT be using static variable to create your GUI. I suggest you read the section from the Swing tutorial on Layout Manager. The tutorial will give you more information and the example code will show you how to better structure your program so that you don't need to use static variables.