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How do I add a scrollbar to a JFrame with setLayout(null)?

I have some components which I need to use setBounds() on, hence the reason why I'm using the setLayout(null).
But some of my components are out the window(below the Y-axis). I was wondering if there is a way to add a scrollbar to navigate down the window so as to see all the remaining components. A screenshot of my window is below.
Output of my window image:

That GUI would be simple to produce using layouts. Put the component displaying the list (which looks well suited to being a JTable, given the two pieces of data per row / line) into a JScrollPane. Put the scroll pane into the CENTER of a BorderLayout. Put the red label into the PAGE_START of the border layout. Then .. oh wait, the job is done!
This is what it might look like (using a JTextArea instead of a table).
can u please post a copy of this code.
Try implementing it based on the instructions above. If there is a problem, post a minimal reproducible example of your attempt.

Since you are refering to the items in the scrolling area as components, and not as texts in a JTextArea, please have a look at the below.
import java.awt.*;
import javax.swing.*;
import java.util.Random;
public class Mainframe {
private JFrame f;
Box box;
JScrollPane scrollPane;
Random rand = new Random();
public static void main(String[] args) {
new Mainframe().go();
}
private void go() {
box = new Box(BoxLayout.Y_AXIS);
JLabel label = new JLabel("Possible Paths and Total Distances");
label.setForeground(Color.RED);
for (int i = 0; i < 200; i++) {
box.add(Box.createRigidArea(new Dimension(0, 2)));// creates space between the components
box.add(new JLabel(i + " : " + rand.nextInt(10000)));
}
scrollPane = new JScrollPane(box);
Dimension dim = new Dimension(box.getComponent(0).getPreferredSize());
scrollPane.getVerticalScrollBar().setUnitIncrement(dim.height * 2); // adjusts scrolling speed
//scrollPane.getViewport().setBackground(Color.WHITE);
f = new JFrame();
f.getContentPane().add(label, BorderLayout.NORTH);
f.getContentPane().add(scrollPane, BorderLayout.CENTER);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(640, 480);
f.setLocationRelativeTo(null);
f.setVisible(true);
}
}

Prepend text to JTextArea without scrolling up (java swing)

If I want to prevent the JTextArea from scrolling to the bottom when I add text to the end, the solution is very simple: Just set the caret's update policy to DefaultCaret.NEVER_UPDATE before calling the JTextArea's append method. I am trying to do the same thing (load the text without scrolling), but for prepending text instead of appending text.
I have tried lots of things. One of them is this, but it doesn't work:
public void loadMoreUp(){
caret = (DefaultCaret)ta.getCaret(); // ta is a JTextArea
caret.setUpdatePolicy(DefaultCaret.NEVER_UPDATE); //doesn't work
String s = "The new text\n";
ta.setText(s + ta.getText()); // I have also tried with ta.getDocument().insertString(0,s,null)
}
The behavior I want is that "The new text" gets prepended to the top, but the JTextArea doesn't scroll up with it. "The new text" should not be visible unless the user manually scrolls up to see it.
How can I prepend text to the top of a JTextArea, without it scrolling up? My JTextArea is in a JScrollPane if that is relevant.

So it turns out that making your JTextArea uneditable is what's keeping the scrollbar at the top. I don't think prepending text is moving it -- it's more the case that it never moves at all.
If the goal is simply to keep the scrollbar scrolled all the way down the scrollpane, however, all you really have to do is set the caret position, and no one should be the wiser.
You can even set the caret position to some previous position by saving .getCaretPosition() and using that value later.
textArea.insert("Mein Hund frisst Nuesse\n", 0);
textArea.setCaretPosition(textArea.getDocument().getLength());
You can see my full example here, which you can use to reconcile against your implementation.
import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.JScrollPane;
import java.awt.Dimension;
import javax.swing.JButton;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Foo extends JFrame implements ActionListener
{
JTextArea textArea;
JScrollPane scrollPane;
JButton button;
public Foo()
{
textArea = new JTextArea();
textArea.setEditable(false);
textArea.setText("a\nb\nc\nd\ne\nf\ng\nh\ni\nj\nk\nl\nm\nn\no\np\nq\nr\ns\nt\nu\nv\nw\nx\ny\nz\n");
scrollPane = new JScrollPane(textArea);
scrollPane.setPreferredSize(new Dimension(400, 200));
button = new JButton("Prepend");
button.addActionListener(this);
this.add(button, BorderLayout.PAGE_END);
this.add(scrollPane, BorderLayout.PAGE_START);
}
public void actionPerformed(ActionEvent e)
{
if(e.getSource() == button)
{
textArea.insert("Mein Hund frisst Nuesse\n", 0);
textArea.setCaretPosition(textArea.getDocument().getLength());
//textArea.setText("Mein Hund frisst Nuesse\n" + textArea.getText());
}
}
public static void main(String[] args)
{
Foo f = new Foo();
f.setPreferredSize(new Dimension(500, 300));
f.pack();
f.setVisible(true);
}
}

The following code seems to work:
public void loadMoreUp(){
caret.setUpdatePolicy(DefaultCaret.NEVER_UPDATE);
String s = "The new text\n";
JScrollBar vbar = scrollPane.getVerticalScrollBar();
int diff = vbar.getMaximum() - vbar.getValue();
try{
ta.getDocument().insertString(0, s, null);
}
catch(BadLocationException e){
logger.error("Bad Location");
}
SwingUtilities.invokeLater(new Runnable(){
public void run(){
vbar.setValue(vbar.getMaximum()-diff);
}
});
}
The basic idea is to remember the position relative to the END of the document (vbar.getMaximum() - vbar.getValue()), and then restore this value after prepending the text.
invokeLater is needed, otherwise getMaximum runs before its value gets updated. The drawback with this method is that invokeLater makes the text briefly flicker.

How to disable text selection on JTextArea Swing

I don't want the user to select the content on JTextArea. I use setEditable(false) but it's not working. How to disable this feature of JTextArea component. Could you give me advise. Thanks.

If you would like to just disable text selection on any swing control such as JtextArea you can use the coding below:
JtextArea.setHighlighter(null);
This one line of coding will help disable the text selection and can be placed in the constructor or within a initialized method upon Frame execution.
Hope this helps

You can set the "mark" equal to the "dot" of the caret. When these values are equal there is no text selection:
import java.awt.*;
import javax.swing.*;
import javax.swing.text.*;
public class NoTextSelectionCaret extends DefaultCaret
{
public NoTextSelectionCaret(JTextComponent textComponent)
{
setBlinkRate( textComponent.getCaret().getBlinkRate() );
textComponent.setHighlighter( null );
}
#Override
public int getMark()
{
return getDot();
}
private static void createAndShowUI()
{
JTextField textField1 = new JTextField("No Text Selection Allowed");
textField1.setCaret( new NoTextSelectionCaret( textField1 ) );
textField1.setEditable(false);
JTextField textField2 = new JTextField("Text Selection Allowed");
JFrame frame = new JFrame("No Text Selection Caret");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(textField1, BorderLayout.NORTH);
frame.add(textField2, BorderLayout.SOUTH);
frame.pack();
frame.setLocationByPlatform( true );
frame.setVisible( true );
}
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowUI();
}
});
}
}

Late to the party, but here are my findings. I had tried using setEnabled(false) on a JTextPane displaying static (not user-modifiable) content such as line numbers (for another text component). This one alone prevents the component from getting focus and text selection on it:
JTextArea textArea = new JTextArea("Static text");
textArea.setEnabled(false);
My problem with setEnabled(false) is that it forces a single disabledTextColor for all of the text (I've traced it down to javax.swing.text.GlyphView.paint()), while I want to style individual lines/chunks. I've finally tried setFocusable(false) that appears to satisfy both needs:
Not user focusable and no user selection on it;
Custom text color could be applied to individual parts of the content, or it just doesn't change the text color to the disabled one.
The complete solution needs additional setEditable(false) to prevent the mouse cursor from changing but that's it – two properties:
JTextArea textArea = new JTextArea("Static text");
textArea.setEditable(false);
textArea.setFocusable(false);

JLabel setText not updating text

I am trying to update a JLabel by using the setText() method, but I can't redraw JLabel. Do I have to use the repaint() method to do that?
Here is the part of code, I do not get any errors, but it is not updating the JLabel.
public void actionPerformed(ActionEvent e) {
fc = new JFileChooser();
if(e.getSource() == addButton) {
int returnVal = fc.showOpenDialog(Main.this);
if (returnVal == JFileChooser.APPROVE_OPTION) {
filesList = fc.getSelectedFiles();
setFilesList(filesList);
StringBuilder logString = new StringBuilder();
logString.append("Files to Convert " + "\n");
for(int i = 0; i < getFiles().length; i++) {
logString.append(filesList[i].getAbsolutePath());
}
//JLabel log = new JLabel(); created above.
log.setText(logString.toString());
} else {
//log.append("Open command cancelled by user." + newline);
}
//log.setCaretPosition(log.getDocument().getLength());
}
}

JLabel requires no repaint call. Simply calling setText(...) will change the label's text, and that is all that is required.
I wonder if your problem is a concurrency issue, that you are doing a long-running process on the Swing event thread and that this is preventing your label from updating its text.
If so, then consider doing your long-running process in a background thread such as that provided by a SwingWorker, and then updating your JLabel's text on the Swing thread, such as can be done via the SwingWorker's publish/process methods.
For more on this, please have a look at the Lesson: Concurrency in Swing tutorial.
Also Mario De... is correct about not being able to print simple new-lines on a JLabel. 1+ to his answer.

I'm a bit stumped on how the repainting of frames/component works in Java. You can Paint(Graphics g), update(Graphics g) which according to the javadoc just calls paint(g). Finally there's also repaint()...
If none of those seem to work, wouldn't it just be easier to create the label only at the line where you are currently trying to set the text?
Edit: there is also the option of using an ineditable textArea. Not only can it display the standard newline character, but you can put it in a jScrollPane, which is handy when you have lots of files in the log, and you don't need to repaint text components to display updated text. The bonus is magnificent imo...

This simple example works for me so problem is not JLabel but some bug in other part of your source code. Please post full source code.
import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.GridLayout;
import java.awt.Panel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class Application {
public static void main(String[] args) {
JFrame frame = new JFrame("JLabel test");
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Panel p = new Panel();
p.setLayout(new GridLayout());
Button button = new Button("Change");
final JLabel label = new JLabel(Long.toString(Long.MAX_VALUE));
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
label.setText(Long.toString(e.getWhen()));
}
});
p.add(button);
p.add(label);
frame.add(p, BorderLayout.NORTH);
frame.pack();
}
}

I have run into a similar problem. I tried to setText("Good Bye") in actionPerformed() in an exit button ActionListener before disposing my JFrame right there, but the text was not changing.
Eventually I realized that my label was not getting updated as I was disposing the frame in the anonymous ActionListener class. After I had let the code leave ActionListener.actionPerformed(), the label text got updated.
I had to dispose my JFrame in a new thread though to ensure that:
actionPerformed is finished so that the main thread returns from the anonymous nested class and updates the label in the main class.
A new thread is started which waits for a second to allow "Good Bye" to be read.
This new thread the disposes the frame.

repaint() won't work here.
Simply use label_name.paintImmediately(label_name.getVisibleRect());
It will get updated right away.

Please try -
jlabel.setText("Your Text");
jLabel.setVisisble(true);

How can I display red text in a JTextArea?

I want to show error(text) in result in red color after compiling exec file
and display it in textarea of gui using swing in java.

A normal JTextArea doesn't support fancy things like different colors of text. However, there are similar components that do. See http://java.sun.com/docs/books/tutorial/uiswing/components/text.html

JEditorPane can get content formatted in HTML. The official Sun tutorial also gives some insight:
The JTextArea class provides a component that displays multiple lines of text and optionally allows the user to edit the text. If you need to obtain only one line of input from the user, you should use a text field. If you want the text area to display its text using multiple fonts or other styles, you should use an editor pane or text pane. If the displayed text has a limited length and is never edited by the user, use a label.

Here's a quick example of adding text to a JEditorPane using AttributeSet and StyleConstants.
This brings up a little frame with a JEditorPane and you can use it to add text of lots of colors without using HTML.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.text.*;
import javax.swing.border.*;
public class TextColor extends JFrame implements ActionListener {
JTextPane myTextPane;
JTextArea inputTextArea;
public TextColor() {
super();
JPanel temp = new JPanel(new BorderLayout());
inputTextArea = new JTextArea();
JButton btn = new JButton("Add");
btn.addActionListener(this);
temp.add(btn, BorderLayout.SOUTH);
temp.add(inputTextArea, BorderLayout.NORTH);
this.getContentPane().add(temp, BorderLayout.SOUTH);
myTextPane = new JTextPane();
myTextPane.setBorder(new EtchedBorder());
this.getContentPane().add(myTextPane, BorderLayout.CENTER);
this.setSize(600, 600);
this.setVisible(true);
}
public void actionPerformed(ActionEvent ae) {
Color newTextColor = JColorChooser.showDialog(this, "Choose a Color", Color.black);
//here is where we change the colors
SimpleAttributeSet sas = new SimpleAttributeSet(myTextPane.getCharacterAttributes());
StyleConstants.setForeground(sas, newTextColor);
try {
myTextPane.getDocument().insertString(myTextPane.getDocument().getLength(),
inputTextArea.getText(), sas);
} catch (BadLocationException ble) {
ble.printStackTrace();
}
}
public static void main(String args[]) {
new TextColor();
}
}

Smita,
take care to paste snippet of your code so that one can understand where exactly problem is or help is required.
Coming to your problem,
To the best of my knowledge, there is no way to set different colors for different text elements in textArea in java. You can set only one color for all.
Alternative is to use JTextPane.
See if following code helps your cause.
String text = "Some Text..."; //This can be any piece of string in your code like
output of your program...
JTextPane myTextPane = new JTextPane();
SimpleAttributeSet sas = new SimpleAttributeSet(myTextPane.getCharacterAttributes());
// As what error you were referring was not clear, I assume there is some code in your
program which pops out some error statement. For convenience I use Exception here..
if( text.contains("Exception") ) //Checking if your output contains Exception...
{
StyleConstants.setForeground(sas, Color.red); //Changing the color of
StyleConstants.setItalic(sas, true);
try
{
myTextPane.getDocument().insertString
(
myTextPane.getDocument().getLength(),
text + "\n",
sas
);
}
catch( BadLocationException ble )
{
text.append(ble.getMessage());
}
}
else
{
StyleConstants.setForeground(sas, Color.GREEN);
try
{
myTextPane.getDocument().insertString
(
myTextPane.getDocument().getLength(),
text + "\n",
sas
);
}
catch(BadLocationException ble)
{
text.append(ble.getMessage());
}
}
I guess this will solve your problem with few modifications.
Thanks.
Sushil