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JDesktopPane not displaying any component

I'm experimenting with desktop panes so I can use them in my work projects. The problem here is that I want to use an JInternalFrame within a JDesktopPane, in a normal JPanel it shows normally but cannot move it, using the desktop pane doesn't display any component added.
Here is the code of the last try, is simple just for learning how it works:
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Internal_FrameShowtst extends JFrame{
Internal_FrameShowtst(){
BorderLayout bl = new BorderLayout();
JDesktopPane p = new JDesktopPane();
JPanel p1 = new JPanel();
JButton b = new JButton("click");
JInternalFrame in = new JInternalFrame("Test");
Internal_Frametst ift = new Internal_Frametst();
b.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
//p1.add(new JLabel("hola"));
//in.add(p1);
//in.setVisible(true);
ift.setVisible(true);
}
});
p1.add(b);
bl.addLayoutComponent(p,BorderLayout.CENTER);
//p.add(in);
p.add(ift);
p.repaint();
setLayout(bl);
add(p);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Internal_FrameShowtst().setVisible(true);
}
});
}
}
custom internal frame class:
import javax.swing.*;
public class Internal_Frametst extends JInternalFrame {
Internal_Frametst(){
JPanel p = new JPanel();
JLabel label = new JLabel("Halo");
setIconifiable(true);
//setIcon(true);
setClosable(true);
p.add(label);
p.setSize(300,300);
add(p);
//setVisible(true);
}
}
I've read and tried the following:
Components inside JDesktopPane not showing
JDesktopPane not displaying components when adding JInternalFrame
I've tried adding the components directly, adding a JPanel, adding the internal frame, trying without it, creating the internal frame in the main class, creating my own internal frame in its own class, using layout managers with both panels (normal and desktop), all with the same result.

Your code creates several components that are never added to the visible UI at all. In the version you have posted, the internal frame is invisible and the button to make it visible is not part of the frame. But there are also problems with the initial sizes of the components.
I strongly recommend to keep the creation of a component, the setting of its initial properties, and the code to add it to a parent component close together in your source code.
Further, consider the points discussed in Prefer composition over inheritance? Your subclasses are entirely unnecessary.
Here is a revised version of your code that will open the internal frame when the button is clicked:
import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.*;
public class UiExample {
public static void main(String[] args) {
EventQueue.invokeLater(UiExample::initializeUI);
}
static void initializeUI() {
JPanel p1 = new JPanel();
JButton b = new JButton("Show Internal Frame");
p1.add(b);
JInternalFrame ift = initializeInternalFrame();
b.addActionListener(e -> {
ift.pack();
ift.setVisible(true);
});
JDesktopPane p = new JDesktopPane();
p.add(ift);
JFrame mainFrame = new JFrame();
mainFrame.setSize(300, 200);
mainFrame.getContentPane().add(p, BorderLayout.CENTER);
mainFrame.getContentPane().add(p1, BorderLayout.PAGE_START);
mainFrame.setVisible(true);
}
static JInternalFrame initializeInternalFrame() {
JInternalFrame iFrame = new JInternalFrame();
iFrame.setIconifiable(true);
// setIcon(true);
iFrame.setClosable(true);
iFrame.setDefaultCloseOperation(JInternalFrame.HIDE_ON_CLOSE);
JPanel p = new JPanel();
p.add(new JLabel("Hello"));
iFrame.add(p);
return iFrame;
}
}
Note that setDefaultCloseOperation(JInternalFrame.HIDE_ON_CLOSE) is necessary for being able to show the frame again via setVisible(true) after the internal frame has been closed.

How can I add ScrollBar to JTextArea in Java Swing?

Anyone help me how to add a scroll bar to a JTextArea with Swing in Java?
The JTextArea just disappear when I add the scroll bar on it.
Hope somebody get me add a vertical scrollbar on it.
Additional explanation will be very thankful
public class Practice extends JFrame {
JFrame frame = new JFrame("AAA");
JTextArea textarea = new JTextArea();
JScrollPane scroll = new JScrollPane(textarea);
JPanel panelForScroll = new JPanel(null);
public Practice(){
frame.setLayout(null);
frame.setBounds(100,100,400,710);
frame.setResizable(false);
frame.setVisible(true);
textarea.setEditable(false);
textarea.setFont(new Font("arian", Font.BOLD, 16));
textarea.setBounds(20, 280, 340, 70);
panelForScroll.add(scroll);
frame.add(panelForScroll); //can't find text area....
}
public static void main(String[] args) {
new Practice();
}
}

There are several errors in your code:
You're using a null layout, this is discouraged as it produces more problems than solutions, specially when you try to use JScrollPanes, since they take the preferredSize of the Component to decide whether to add the scroll bars or not. See Why is it frowned upon to use a null layout in Swing? for more information about this. To fix this, remove this line:
frame.setLayout(null);
And instead use a layout manager or combinations of them along with borders for extra spacing between components.
While null layouts might seem like the best, easiest and faster way to design complex GUIs for Swing newbies, the more you progress in it, the more problems related to the use of them you'll find (as it's the case)
You're extending your class from JFrame and you're creating an instance of JFrame in it too, please use one or the other. When you extend JFrame you're saying your class is a JFrame and thus it cannot be placed inside another Container because JFrame is a rigid container. I recommend to forget the extends JFrame part, since anyway you're not using the JFrame that is generated by this action and stay with the object you created. See https://stackoverflow.com/questions/41252329/java-swing-using-extends-jframe-vs-calling-it-inside-of-class for a more detailed answer about this problem.
You're making your GUI visible before you have added all the elements, this could cause your GUI to not display all the elements until you hover over them, this line:
frame.setVisible(true);
Should be one of the last lines in your program
You're not placing your program on the Event Dispatch Thread (EDT) which makes your application to not be thread safe, you can fix it by writing this on your main method.
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
//Place your constructor here
}
});
You're setting bounds for the textArea but not for the scrollPane, but you should really not be setting the bounds manually (see point #1 again).
Now, you can make a simple GUI with a JTextArea with a JScrollPane as follows:
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
public class ScrollPaneToTextArea {
private JTextArea textArea;
private JFrame frame;
private JScrollPane scroll;
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new ScrollPaneToTextArea().createAndShowGui();
}
});
}
public void createAndShowGui() {
frame = new JFrame("ScrollPane to TextArea");
textArea = new JTextArea(10, 20); //Rows and cols to be displayed
scroll = new JScrollPane(textArea);
// scroll = new JScrollPane(textArea, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
frame.add(scroll); //We add the scroll, since the scroll already contains the textArea
frame.pack();
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
Which produces this output and the scroll bars are added when needed (i.e. when text goes further than the rows it can handle in the view)
If you want the vertical scroll bars to appear always you can uncomment the line:
scroll = new JScrollPane(textArea, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
Which will produce the following outputs:
You can read more about JScrollPane in the docs and JTextArea also in their own docs.

JPanel panelForScroll = new JPanel(null);
This sets the NULL Layout to this JPanel. This would require more configuration (just as you did for the frame object).
Just remove the null (also from frame.setLayout(null)!)

You have to use Jtextpane to get the scroll bar on textarea.
JTextArea ta = new JTextArea();
JScrollPane sp = new JScrollPane(ta);
JFrame f = new JFrame();
f.getContentPane().add(sp);

you are setting the panel's layout to null,then you didn't specify the scroll bar bounds. Since you only have one component in your panel which is the scroll bar I recommend using FlowLayout

How to display one Jframe at a time? [duplicate]

I'm trying to make a little game that will first show the player a simple login screen where they can enter their name (I will need it later to store their game state info), let them pick a difficulty level etc, and will only show the main game screen once the player has clicked the play button. I'd also like to allow the player to navigate to a (hopefully for them rather large) trophy collection, likewise in what will appear to them to be a new screen.
So far I have a main game window with a grid layout and a game in it that works (Yay for me!). Now I want to add the above functionality.
How do I go about doing this? I don't think I want to go the multiple JFrame route as I only want one icon visible in the taskbar at a time (or would setting their visibility to false effect the icon too?) Do I instead make and destroy layouts or panels or something like that?
What are my options? How can I control what content is being displayed? Especially given my newbie skills?

A simple modal dialog such as a JDialog should work well here. The main GUI which will likely be a JFrame can be invisible when the dialog is called, and then set to visible (assuming that the log-on was successful) once the dialog completes. If the dialog is modal, you'll know exactly when the user has closed the dialog as the code will continue right after the line where you call setVisible(true) on the dialog. Note that the GUI held by a JDialog can be every bit as complex and rich as that held by a JFrame.
Another option is to use one GUI/JFrame but swap views (JPanels) in the main GUI via a CardLayout. This could work quite well and is easy to implement. Check out the CardLayout tutorial for more.
Oh, and welcome to stackoverflow.com!

Here is an example of a Login Dialog as #HovercraftFullOfEels suggested.
Username: stackoverflow Password: stackoverflow
import java.awt.*;
import java.awt.event.*;
import java.util.Arrays;
import javax.swing.*;
public class TestFrame extends JFrame {
private PassWordDialog passDialog;
public TestFrame() {
passDialog = new PassWordDialog(this, true);
passDialog.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new TestFrame();
frame.getContentPane().setBackground(Color.BLACK);
frame.setTitle("Logged In");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
}
});
}
}
class PassWordDialog extends JDialog {
private final JLabel jlblUsername = new JLabel("Username");
private final JLabel jlblPassword = new JLabel("Password");
private final JTextField jtfUsername = new JTextField(15);
private final JPasswordField jpfPassword = new JPasswordField();
private final JButton jbtOk = new JButton("Login");
private final JButton jbtCancel = new JButton("Cancel");
private final JLabel jlblStatus = new JLabel(" ");
public PassWordDialog() {
this(null, true);
}
public PassWordDialog(final JFrame parent, boolean modal) {
super(parent, modal);
JPanel p3 = new JPanel(new GridLayout(2, 1));
p3.add(jlblUsername);
p3.add(jlblPassword);
JPanel p4 = new JPanel(new GridLayout(2, 1));
p4.add(jtfUsername);
p4.add(jpfPassword);
JPanel p1 = new JPanel();
p1.add(p3);
p1.add(p4);
JPanel p2 = new JPanel();
p2.add(jbtOk);
p2.add(jbtCancel);
JPanel p5 = new JPanel(new BorderLayout());
p5.add(p2, BorderLayout.CENTER);
p5.add(jlblStatus, BorderLayout.NORTH);
jlblStatus.setForeground(Color.RED);
jlblStatus.setHorizontalAlignment(SwingConstants.CENTER);
setLayout(new BorderLayout());
add(p1, BorderLayout.CENTER);
add(p5, BorderLayout.SOUTH);
pack();
setLocationRelativeTo(null);
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
jbtOk.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (Arrays.equals("stackoverflow".toCharArray(), jpfPassword.getPassword())
&& "stackoverflow".equals(jtfUsername.getText())) {
parent.setVisible(true);
setVisible(false);
} else {
jlblStatus.setText("Invalid username or password");
}
}
});
jbtCancel.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
setVisible(false);
parent.dispose();
System.exit(0);
}
});
}
}

I suggest you insert the following code:
JFrame f = new JFrame();
JTextField text = new JTextField(15); //the 15 sets the size of the text field
JPanel p = new JPanel();
JButton b = new JButton("Login");
f.add(p); //so you can add more stuff to the JFrame
f.setSize(250,150);
f.setVisible(true);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Insert that when you want to add the stuff in. Next we will add all the stuff to the JPanel:
p.add(text);
p.add(b);
Now we add the ActionListeners to make the JButtons to work:
b.addActionListener(this);
public void actionPerforemed(ActionEvent e)
{
//Get the text of the JTextField
String TEXT = text.getText();
}
Don't forget to import the following if you haven't already:
import java.awt.event*;
import java.awt.*; //Just in case we need it
import java.x.swing.*;
I hope everything i said makes sense, because sometimes i don't (especially when I'm talking coding/Java) All the importing (if you didn't know) goes at the top of your code.

Instead of adding the game directly to JFrame, you can add your content to JPanel (let's call it GamePanel) and add this panel to the frame. Do the same thing for login screen: add all content to JPanel (LoginPanel) and add it to frame. When your game will start, you should do the following:
Add LoginPanel to frame
Get user input and load it's details
Add GamePanel and destroy LoginPanel (since it will be quite fast to re-create new one, so you don't need to keep it memory).

JButton not changing size

I've researched the ways to change the size of a jbutton to be displayed on a JFrame.
I am trying both the button.setSize(200,200) and button.setPreferredSize(new Dimension(200,200)), but it does not change. Here's the code:
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JButton;
import javax.swing.JFrame;
public class Index extends JFrame{
private String title = "This is the motherfucking title";
Dimension dim = new Dimension(500,500);
public Index(){
this.setResizable(false);
this.setTitle(title);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(dim);
this.getContentPane().setBackground(Color.BLACK);
JButton button = new JButton("Button");
button.setSize(200,200);
this.add(button);
}
public static void main(String args[]){
Index ih = new Index();
ih.setVisible(true);
}
}
Here's the result: http://i.imgur.com/Llj0pfo.png
What am I doing wrong?

try this:
JButton button = new JButton("Button");
button.setSize(200,200);
getContentPane().setLayout(null);
getContentPane().add(button);
setVisible(true);
inside your constructor.

this.add(button);
You are adding the button to the content pane of the frame. By default the content uses a BorderLayout and the component is added to the CENTER. Any component added to the CENTER will automatically get the extra space available in the frame. Since you set the size of the frame to (500, 500) there is lots of space available.
As a general rule you should NOT attempt to set the preferred size of a component, since only the component know how big it should be in order to paint itself properly. So your basic code should be:
JButton button = new JButton("...");
frame.add(button);
frame.pack();
frame.setVisible(true);
Now the button will be at its preferred size. However, the button will change size if you resize the frame. If you don't want this behaviour, then you need to use a different Layout Manager.

Use SwingUtilities.invokeLater(); create your Index() inside it, then call setVisible(true); at the end of constructor. At the same time remeber that by default JFrame uses BorderLayout.
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
new Index();
}
});

Aligning components in Box

edit: if you downvote this question, you may leave a comment to explain why, that will be more constructive.
I obtain this unexpected result...
... using this code:
import javax.swing.Box;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;
public class TestAlignment extends JFrame {
// Constructor
public TestAlignment() {
super("Test Alignment");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Components to show
JLabel leftLabel = new JLabel("Left");
JButton centerButton = new JButton("Middle");
JLabel rightLabel = new JLabel("Right");
// Add all to box
Box box = Box.createVerticalBox();
box.add(leftLabel);
box.add(centerButton);
box.add(rightLabel);
box.add(Box.createHorizontalStrut(180));
// Align content in box
leftLabel.setAlignmentX(LEFT_ALIGNMENT);
centerButton.setAlignmentX(CENTER_ALIGNMENT);
rightLabel.setAlignmentX(RIGHT_ALIGNMENT);
// Add box to frame, and show frame
box.setOpaque(true);
setContentPane(box);
setVisible(true);
}
// Main
public static void main(String[] args) {
// Create frame in EDT
SwingUtilities.invokeLater(new Runnable() {
#Override public void run() { new TestAlignment(); }
});
}
}
I understand now this works as expected for JComponent.setAlignmentX(): this method tells which sides of the components must be aligned (top label leftmost side aligned with button center and bottom label rightmost side).
I would like to understand how to have each label aligned as expected intuitively (left label on the left, right label on the right), labels touching the vertical edges of the Box?
(I know how to do with putting each label in a Box embedded, and using Box.createHorizontalGlue() to force it to the left or the right side, but seems to me too much for the simple purpose of alignment. I'm looking for something more simple)

Don't think you can do this with a BoxLayout. Your example does show the intuitive code, which doesn't work as you would hope.
I would suggest you probably need to use a GridBagLayout. I think it supports the setAlignmentX(...) method the way you want to use it.
If not, then can use the Relative Layout. It is simple to use, like the BoxLayout and does support the alignment you want when you use:
setAlignment( RelativeLayout.COMPONENT );

You can use BoxLyout:
// Components to show
// Left
JLabel leftLabel = new JLabel("Left");
JPanel leftPanel = new JPanel();
leftPanel.setLayout(new BoxLayout(leftPanel, BoxLayout.X_AXIS));
leftPanel.add(leftLabel);
leftPanel.add(Box.createHorizontalGlue());
// Center
JButton centerButton = new JButton("Middle");
// Right
JLabel rightLabel = new JLabel("Right");
JPanel rightPanel = new JPanel();
rightPanel.setLayout(new BoxLayout(rightPanel, BoxLayout.X_AXIS));
rightPanel.add(Box.createHorizontalGlue());
rightPanel.add(rightLabel);
// Add all to box
Box box = Box.createVerticalBox();
box.add(leftPanel);
box.add(centerButton);
box.add(rightPanel);
box.add(Box.createHorizontalStrut(180));
// Align content in box
// leftLabel.setAlignmentX(LEFT_ALIGNMENT);
centerButton.setAlignmentX(CENTER_ALIGNMENT);
// rightLabel.setAlignmentX(RIGHT_ALIGNMENT);