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Adding JScrollPane to JPanel with another panels inside

i been working on some bigger project lately but couldn't figure it out why JScrollPane wouldn't work. I have never used it before and I read many solved problems about it on stackOverflow and other programming forums but non of the code were looking similar to mine to help me implement my method.
this is new project i made to make it short and show some examples.
Red colour is main panel that will contain another panel/JScrollPane inside that will be colour black
and i would like to make this Jpanel with colour black to be scrollable and hold any number of that white JPanels that might be from 0 to a 100+
public class ScrollablePane {
private JFrame frame;
private JPanel panelCopy;
private JPanel panel;
private JPanel container;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
ScrollablePane window = new ScrollablePane();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public ScrollablePane() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
panel = new JPanel();
panel.setBackground(Color.RED);
panel.setBounds(0, 0, 434, 261);
frame.getContentPane().add(panel);
panel.setLayout(null);
container = new JPanel();
container.setBackground(Color.BLACK);
container.setBounds(10, 10, 414, 241);
container.setLayout(new FlowLayout(FlowLayout.CENTER, 10, 10));
panel.add(container);
for(int i = 0; i < 20; i++) {
if(i > 0) {
panelCopy = new JPanel();
panelCopy.setPreferredSize(new Dimension(400, 40));
container.add(panelCopy);
}
}
}
}

if you want to use a JScrollPane, then your code actually needs to use a JScrollPane. The code you posted doesn't even create a JScrollPane.
If you want the panels to display vertically then don't use a FlowLayout. The FlowLayout is a horizontal layout. You could use a BoxLayout or a GridBagLayout.
Why do you create the "panel" variable and add it the the content pane? The content pane of the frame already is a JPanel that uses a BorderLayout. There is no need to add another panel
Don't use a null layout!!! Swing was designed to be used with layout managers. Scrolling won't work if the panel added to the scroll pane uses a null layout.
So in your case the basic logic might be something like:
Box container = Box.createVerticalBox();
// add you child panels to the container.
JPanel wrapper = new JPanel( new BorderLayout() );
wrapper.add(container, BorderLayout.PAGE_START);
JScrollPane scrollPane = new JScrollPane(wrapper);
frame.add(scrollPane, BorderLayout.CENTER);
Note the "wrapper" panel is used to prevent the panels from expanding in size when the scroll pane is larger then the preferred size of the "container" panel.
Try:
//JScrollPane scrollPane = new JScrollPane(wrapper);
JScrollPane scrollPane = new JScrollPane(container);
to see the different result.

How to Add text to JTextArea

Im creating a programme using java. I want the user to enter some text, then push the button so the text entered shows in the label. However, I have 2 problems. First, the text are isn´t displaying when I execute the app. Second, I don´t know how to allow the user to type in the area. Im new in java so that´s why Im asking. Here is the code. Thank you.
import javax.swing.*;
import java.awt.event.*;
class Boton extends JFrame implements ActionListener {
JButton boton;
JTextArea textArea = new JTextArea();
JLabel etiqueta = new JLabel();
public Boton() {
setLayout(null);
boton = new JButton("Escribir");
boton.setBounds(100, 150, 100, 30);
boton.addActionListener(this);
add(boton);
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == boton) {
try {
String texto = textArea.getText();
etiqueta.setText(texto);
Thread.sleep(3000);
System.exit(0);
} catch (Exception excep) {
System.exit(0);
}
}
}
}
public class Main{
public static void main(String[] ar) {
Boton boton1 =new Boton();
boton1.setBounds(0,0,450,350);
boton1.setVisible(true);
boton1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

Problems:
You never add the JTextArea into your GUI, and if it doesn't show, a user cannot directly interact with it.
You are calling Thread.sleep on the Swing event thread, and this will put the entire application to sleep, meaning the text that you added will not show.
Other issues include use of null layouts and setBounds -- avoid doing this.
Solutions:
Set the JTextArea's column and row properties so that it sizes well.
Since your JTextArea's text is going into a JLabel, a component that only allows a single line of text, I wonder if you should be using a JTextArea at all. Perhaps a JTextField would work better since it allows user input but only one line of text.
Add the JTextArea to a JScrollPane (its viewport actually) and add that to your GUI. Then the user can interact directly with it. This is most easily done by passing the JTextArea into a JScrollPane's constructor.
Get rid of the Thread.sleep and instead, if you want to use a delay, use a Swing Timer. check out the tutorial here
For example:
import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.Window;
import java.awt.event.KeyEvent;
import javax.swing.*;
public class Main2 {
public static void main(String[] args) {
// create GUI in a thread-safe manner
SwingUtilities.invokeLater(() -> createAndShowGui());
}
private static void createAndShowGui() {
BotonExample mainPanel = new BotonExample();
JFrame frame = new JFrame("GUI");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
}
class BotonExample extends JPanel {
private JLabel etiqueta = new JLabel(" ");
private JButton boton = new JButton("Escribir");
// jtext area rows and column properties
private int rows = 5;
private int columns = 30;
private JTextArea textArea = new JTextArea(rows, columns);
public BotonExample() {
// alt-e will activate button
boton.setMnemonic(KeyEvent.VK_E);
boton.addActionListener(e -> {
boton.setEnabled(false); // prevent button from re-activating
String text = textArea.getText();
etiqueta.setText(text);
// delay for timer
int delay = 3000;
Timer timer = new Timer(delay, e2 -> {
// get current window and dispose ofit
Window window = SwingUtilities.getWindowAncestor(boton);
window.dispose();
});
timer.setRepeats(false);
timer.start(); // start timer
});
// create JPanels to add to GUI
JPanel topPanel = new JPanel(new FlowLayout(FlowLayout.LEADING, 5, 5));
topPanel.add(new JLabel("Etiqueta:"));
topPanel.add(etiqueta);
JPanel bottomPanel = new JPanel();
bottomPanel.add(boton);
JScrollPane scrollPane = new JScrollPane(textArea);
// use layout manager and add components
setLayout(new BorderLayout());
add(topPanel, BorderLayout.PAGE_START);
add(scrollPane, BorderLayout.CENTER);
add(bottomPanel, BorderLayout.PAGE_END);
}
}

textarea.setText("Text"); // this will insert text into the text area
textarea.setVisable(true); // this will display the text area so you can type in it
textarea.setSize(500,500); // set size of the textarea so it actually shows
The user should be able to type in the TA when it is displayed and just do a getText to pull the text

JPanel Paint does not show on my JFrame [duplicate]

I have a simple Swing GUI. (and not only this, all swing GUI I have written). When run it, it doesn't show anything except blank screen, until I resize the main frame, so every components have painted again, and I can show them.
Here is my simple code :
public static void main(String[] args) {
JFrame frame = new JFrame("JScroll Pane Test");
frame.setVisible(true);
frame.setSize(new Dimension(800, 600));
JTextArea txtNotes = new JTextArea();
txtNotes.setText("Hello World");
JScrollPane scrollPane = new JScrollPane(txtNotes);
frame.add(scrollPane);
}
So, my question is : how can when I start this class, the frame will appear all components I have added, not until I resize frame.
Thanks :)

Do not add components to JFrame after the JFrame is visible (setVisible(true))
Not really good practice to call setSize() on frame rather call pack() (Causes JFrame to be sized to fit the preferred size and layouts of its subcomponents) and let LayoutManager handle the size.
Use EDT (Event-Dispatch-Thread)
call JFrame#setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) as said by #Gilbert Le Blanc (+1 to him) or else your EDT/Initial thread will remain active even after JFrame has been closed
Like so:
public static void main(String[] args) {
//Create GUI on EDT Thread
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new JFrame("JScroll Pane Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JTextArea txtNotes = new JTextArea();
txtNotes.setText("Hello World");
JScrollPane scrollPane = new JScrollPane(txtNotes);
frame.add(scrollPane);//add components
frame.pack();
frame.setVisible(true);//show (after adding components)
}
});
}

Your simple code is missing a few things.
You have to invoke SwingUtilities to put the Swing components on the event dispatch thread.
You should call the setDefaultCloseOperation on the JFrame.
You have to call the JFrame methods in the correct order. The setSize or pack method is called, then the setVisible method is called last.
public class SimpleFrame implements Runnable {
#Override
public void run() {
JFrame frame = new JFrame("JScroll Pane Test");
JTextArea txtNotes = new JTextArea();
txtNotes.setText("Hello World");
JScrollPane scrollPane = new JScrollPane(txtNotes);
frame.add(scrollPane);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(new Dimension(800, 600));
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new SimpleFrame());
}
}

Java Swing blank screen instead of window displayed

I'm following through a book called "The JFC Swing Tutorial (Second Edition)" and I'm pretty much at the start I have followed this code and it should be displaying the button and the label in the content pane, but All im getting is a blank screen. any ideas?
Thanks.
import java.awt.GridLayout;
import javax.swing.*;
public class m extends JFrame
{
void UserFrame()
{
//JFrame.setDefaultLookAndFeelDecorated(true);
JFrame frame = new JFrame("Hellow You");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel jp = new JPanel(new GridLayout(0,1));
//makes label
JLabel label = new JLabel("Sup ");
//adds to the frames content pane a label
frame.getContentPane().add(label);
JButton button = new JButton("Hai");
frame.getContentPane().add(button);
jp.add(button);
jp.add(label);
jp.setBorder(BorderFactory.createEmptyBorder(30,30,10,30));
//pack set the window to what it needs AKA to display all components
frame.pack();
//frame.setSize(250, 250);
//shows window
frame.setVisible(true);
}
public static void main(String[] args)
{
final m window = new m();
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
window.UserFrame();
}
});
}
}

Simply add
frame.add(jp);
just before
frame.pack();
What's happening here? You correctly add all your widgets to a JPane, but you basically threw that JPane away and didn't use it anywhere.
This will be sufficient just to get it to work properly.
If you want to do it correctly, you should also remove frame.getContentPane().add(label); and frame.getContentPane().add(button); (Thank you #dic19 for noting that!). These will not work the way you used it.

Putting multiple JPanels inside a JTabbed pane

I've looked around a while and also played around trying to add multiple panels to a JTabbedPane.
My question is: Is it possible to add the same Jpanel to multiple TabbedPanes. Everything way that I tried, it doesn't seem to work correctly. This is how it it works.
public MainGUI() {
JMenuBar menuBar = new JMenuBar();
setJMenuBar(menuBar);
JTabbedPane tabbedPane = new JTabbedPane(JTabbedPane.TOP);
getContentPane().add(tabbedPane, BorderLayout.CENTER);
JEditorPane instructionalEditorPane = new JEditorPane();
tabbedPane.addTab("Instructional", instructionalEditorPane);
JPanel codePanel = new JPanel();
JPanel drawPanel = new JPanel();
JSplitPane splitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, codePanel, drawPanel);
splitPane.setResizeWeight(0.75);
tabbedPane.addTab("Code Panel", splitPane);
JEditorPane unifiedInstPane = new JEditorPane();
JPanel unifiedCodePanel = new JPanel();
JPanel unifiedDrawPanel = new JPanel();
JSplitPane unifiedSplitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, unifiedCodePanel, unifiedDrawPanel);
unifiedSplitPane.setResizeWeight(0.75);
JSplitPane unifiedPanel = new JSplitPane(JSplitPane.VERTICAL_SPLIT,unifiedInstPane, unifiedSplitPane);
unifiedPanel.setResizeWeight(0.40);
tabbedPane.addTab("Unified Tab", unifiedPanel);
}
What I would like to do is just add the instructionalEditorPane and the splitPane to multiple tabbedPanes but when I do I loose the original Individual tabbedPanes. If I have to I can do it this way but I would then have to write to both the unifiedInstPane & the instructionalEditorPane to keep them updated. I would also have to do this for the 2 splitPanes which have the codePanel and drawPanels embedded. This will make it harder to keep all the panels in sync.
Any suggestions?

"Is it possible to add the same Jpanel to multiple TabbedPanes." -- no. You can only add a component to one container at a time. Your JPanels should share models but use unique components. The model will likely be a non-GUI class of your creation.
For example, here's a very simplistic rendering of my recommendations:
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import javax.swing.*;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;
public class MainGui2 extends JPanel {
private static final int TAB_COUNT = 3;
private JTabbedPane tabbedPane = new JTabbedPane();
private PlainDocument doc = new PlainDocument();
private Action btnAction = new ButtonAction("Button");
public MainGui2() {
for (int i = 0; i < TAB_COUNT; i++) {
tabbedPane.add("Tab " + (i + 1), createPanel(doc, btnAction));
}
setLayout(new BorderLayout());
add(tabbedPane);
}
private JPanel createPanel(PlainDocument doc, Action action) {
JTextArea textArea = new JTextArea(doc);
textArea.setColumns(40);
textArea.setRows(20);
JPanel panel = new JPanel();
panel.add(new JScrollPane(textArea));
panel.add(new JButton(action));
return panel;
}
private class ButtonAction extends AbstractAction {
public ButtonAction(String title) {
super(title);
}
#Override
public void actionPerformed(ActionEvent evt) {
try {
String text = "Button Pressed!\n";
doc.insertString(doc.getLength(), text, null);
} catch (BadLocationException e) {
e.printStackTrace();
}
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("MainGui2");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new MainGui2());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
Better would be to create a formal model class that gets injected into each view, each tabbed pane's individual panes.
Edit
You state in comment:
Yes I can fix that by making calls to the instances but then I'm back to my original problem of having to make calls to each instance to affect a change in all the panel. Say for example I have a drawing panel and I need to call repaint(), I would have to make a call to 2 different instances to get both tabbedPanes to update. Is there any way around this?
Yes, the solution is to use an MVC, or model-view-control, structure. Your model holds your overall program logic, the views are what the user sees, and the control interacts between the two.
Consider having your model notify either the control or the views that its been changed, and then this stimulates a repaint an all observer views.