Develop Reference

Java - Swing - TextArea - scrollbar

I want to have a textArea to display results that can be scrolled. The scrollbar doesn't appear even though I set it to VERTICAL_SCROLLBAR_ALWAYS
What Am I doing wrong??
void addPlayerPanel(JFrame gameFrame) {
JPanel playerPanel = new JPanel();
// automatically added to contentPane with gameFrame.add()
gameFrame.add(playerPanel, BorderLayout.CENTER);
playerPanel.setBorder(new TitledBorder(new EtchedBorder(), "Registered players"));
// text are to show registered players
JTextArea display = new JTextArea(5, 40);
display.setEditable(true); // set textArea to editable
display.setLayout(new FlowLayout(FlowLayout.CENTER, 0, 0));
JScrollPane scroll = new JScrollPane(display);
scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
// Add Text area
playerPanel.add(scroll);
playerPanel.add(display);
}

You're adding both the JScrollPane AND it's display to the GUI -- DON'T do that. Add just the JScrollPane. It holds the display and that is what you need.
So change:
playerPanel.add(scroll);
playerPanel.add(display);
to
playerPanel.add(scroll);
// playerPanel.add(display);
Question: why are you setting the layout manager of your JTextArea? That really makes little sense.

how to add scrollbar to textarea in java

the jscrollpane that I am adding doesnt appearin my textarea
textArea = new JTextArea();
scroll = new JScrollPane(textArea);
scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
this.add(textArea);
this.add(scroll);
this.setSize(1000, 600);
this.setLayout(new BorderLayout());
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);

textArea = new JTextArea();
scroll = new JScrollPane(textArea);
//this.add(textArea); // get rid of this
this.add(scroll);
You create the scrollpane with the text area, but then the next statement removes the text area from the scrollpane because a component can only have a single parent.
Get rid of that statement and just add the scrollpane to the frame.
Then scrollbars will appear automatically as you add data to the text area.
Also you should create the text area using something like:
textArea = new JTextArea(5, 20);
to give a suggestion on how big to make the text area.
I did what you said but still nothing happens
Another problem is that you need to set the layout manager BEFORE you start adding components to the frame (or panel).

Remove this.add(textArea); and add scroll.setSize( 100, 100 ); will also work for you.

JScrollPane opening to bottom of panel

I have a JScrollPane on a panel (which has many panels inside of it) and when I open the frame with the scroll pane on it, the fame is scrolled to the bottom. Is there anyway I can avoid this?
Here are some facts:
The panel the scroller is on contains multiple panels. Some of these panels have text fields. I have tried to set the carat of the text fields to 0 and this did not work.
I know there should be actual code, but when I tried to make a mock pane (as the one I am using is intertwined with a lot of code) it is not replicating the issue.
The panel that is being scrolled is being generated using a loop that generates a series of questions... so a text box, a said amount of buttons/answers, and a text box and label that shows the amount of points for each question.
The last elements of my panel that is being scrolled are a JTextArea and a JLabel.
Below is the code to declare those.
Is there anyone out there that could at least throw out an idea of what would be making the scroll pane automatically go to the bottom?
Here is the declaration of the pane and the panels inside/outside of it
JPanel newPanel = new JPanel(new BorderLayout(0, 0));
JPanel showPanel = new JPanel();
BoxLayout layout = new BoxLayout(showQuizPanel, BoxLayout.Y_AXIS);
showQuizPanel.setLayout(layout);
buttonPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
buttonPanel.setBackground(Color.white);
newPanel.setBackground(Color.white);
showPanel.setBackground(Color.white);
populateButtonPanel();
populateShowPanel(showPanel, buttonPanel);
populateQuestions(showPanel);
JScrollPane scrollPane = new JScrollPane(showPanel, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
scrollPane.getViewport().setBackground(Color.WHITE);
scrollPane.setAlignmentX(JScrollPane.CENTER_ALIGNMENT);
scrollPane.getVerticalScrollBar().setUnitIncrement(16);
scrollPane.getVerticalScrollBar().setValue(0);
scrollPane.getViewport().setViewPosition(new Point(0,0));
newPanel.add(scrollPane, BorderLayout.CENTER);
return newPanel;
code to declare last elements on page
JPanel pPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
pPanel.setBackground(Color.WHITE);
pPanel.add(qValue);
pPanel.add(new JLabel("Points"));
qArea.add(pPanel);
qArea.add(Box.createVerticalStrut(50));
qValue.setCaretPosition(0);
Thanks!

I believe that when you add text to a text area when building the GUI, the scroll pane will scroll to make the text area visible.
So basically you need to reset the scroll pane to the top.
You can use code like the following after adding all components to the scroll pane:
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
scrollPane.getViewport().setViewPosition( new Point(0, 0) );
}
});
The invokeLater() adds the code to the end of the Event Dispatch Thread (EDT) so that it gets executed after the GUI is visible.
Of course this code assumes that you are creating the rest of the GUI properly on the EDT.

Java Positioning a list on a GUI

I'm trying to add a JList to a GUI, but am wondering how to position it? I want it to appear on the right hand side of the TextArea for data that will be sent to the GUI for selection.
Can anyone suggest how to do this? Here is the code (note: very new to Java and GUI's)
protected static void createAndShowGUI() {
GUI predict = new GUI();
JFrame frame = new JFrame("Phone V1.0");
frame.setContentPane(predict.createContentPane());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setMinimumSize(new Dimension(300, 400));
frame.setVisible(true); // Otherwise invisible window
}
private JPanel createContentPane() {
JPanel pane = new JPanel();
TextArea = new JTextArea(5, 10);
TextArea.setEditable(false);
TextArea.setLineWrap(true);
TextArea.setWrapStyleWord(true);
TextArea.setWrapStyleWord(true);
pane.setLayout(new BoxLayout(pane, BoxLayout.Y_AXIS));
//Adds the buttons from Top to Bottom
String[] items = {"dsfsdfd"};
list = new JList(items);
JScrollPane scrollingList = new JScrollPane(list);
int orient = list.getLayoutOrientation();
JPanel window = new JPanel();
pane.add(window);
JPanel buttonPanel = new JPanel();
buttonPanel.setLayout(new GridLayout(5, 3));
JButton[] buttons = new JButton[] {
new JButton("Yes"),
new JButton(""),
new JButton("Clr"),
new JButton("1"),
new JButton("2abc"),
new JButton("3def"),
new JButton("4ghi"),
new JButton("5jkl"),
new JButton("6mno"),
new JButton("7pqrs"),
new JButton("8tuv"),
new JButton("9wxyz"),
new JButton("*+"),
new JButton("0_"),
new JButton("^#")
}; // Array Initialiser
for (int i = 0; i < buttons.length; i++) {
buttonPanel.add(buttons[i]);
buttons[i].addActionListener(this);
}
pane.add(TextArea);
pane.add(list);
pane.add(buttonPanel);
return pane;
}

Read the section from the Swing tutorial on Using Layout Mananger. There is no need to only use a single layout manager. You can nest layout managers to get the desired effect.

Wrap your TextArea and list in a new panel with a BorderLayout manager. Basically the BorderLayout manager lets you arrange components using north, south, east, west and center coordinates. The components at the center takes all available space as the parent container has more space available to it.
private JPanel createContentPane() {
JPanel pane = new JPanel(); //this is your main panel
JPanel textAreaPanel = new JPanel(new BorderLayout()); //the wrapper
//Some more code...
//Then at the end
//Make your TextArea take the center
textAreaPanel.add(TextArea, BorderLayout.CENTER);
//And the list to the east
textAreaPanel.add(list, BorderLayout.EAST);
pane.add(textAreaPanel);
pane.add(buttonPanel);
return pane;
}
The cool thing is that you can nest panels inside other panels, adding them different layout managers to get your desired layout.
On an unrelated note, try to follow Java naming conventions. Instead of JTextArea TextArea use JTextArea textArea. It makes it easier for you and people reading your code to understand it.

You could use a layout manager like Mig Layout for that kind of positionning.
(source: miglayout.com)

I could recommend you FormLayout. Before I found this layout I had a real pain with GridBagLayout. FormLayout is more powerful and much more convenient to learn and use and it is free. Give it a chance.

As others suggested, familiarize yourself with the concept of layout managers. There are several that come with the standard Swing API and several good 3rd party ones out there.
In addition, you will want to add the JList to a scroll pane (JScrollPane). You may want to consider adding it to a split pane (JSplitPane). And by consider I don't mean "do it because some guy on the net said so" I mean "do it if it makes sense for your end users".

How do i get vertical scrolling to JPanel?

I have written a code in java using swing, so that I will have a JscrollPane added to JPanel and then I will add buttons of fixed size to JPanel in vertical fashion
JPanel panel=new JPanel();
panel.setBackground(Color.WHITE);
int v=ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS;
int h=ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS;
JScrollPane jsp=new JScrollPane(panel,v,h);
jsp.setPreferredSize(new Dimension(600,600));
jsp.setBounds(150,670,850,200);
frame.add(jsp);
then I am adding buttons to it at run time.
for(i=0;i<n;i++)
{
button[i]=new JButton();
button[i].setBounds(20,y,120,120);
button[i].setSize(120,120);
button[i].setToolTipText(file[i].toString());
button[i].setIcon(Icon);
panel.add(button[i]);
y=y+140;
}
I want to add a buttons one below the other...(i.e I want a vertical scrollbar)
i.e. button1
button2
'
'
but above code is giving me buttons in a line (i.e. I am getting horizontal scrollbar)
i.e. button1 button2...
another problem is the size of the buttons. Using btn.setSize() is not affecting size at all...
can anybody help me?

You must use an appropriate Layoutmanager like GridLayout, Boxlayout or GridBagLayout for the panel.
It depends what else you want to put into the panel.
GridLayout is easier to use IMO:
JPanel panel = new JPanel();
panel.setLayout(new GridLayout(0, 1)); // any number of rows, 1 column
...
panel.add(button[i]);
BoxLayout is almost as easy:
JPanel panel = new JPanel();
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
...
panel.add(button[i]);
GridBagLayout is more powerful, allowing more than one column, components spanning more than one cell, ... needs a GridBagConstraints to add the elements:
JPanel panel = new JPanel();
panel.setLayout(new GridBagLayout());
GridBagConstraints constraints = new GridBagConstraints(
0, RELATIVE, // x = 0, y = below previous element
1, 1, // cell width = 1, cell height = 1
0.0, 0.0 // how to distribute space: weightx = 0.0, weighty = 0,0
GridBagConstraints.CENTER, // anchor
GridBagConstraints.BOTH, // fill
new Insets(0, 0, 0, 0), // cell insets
0, 0); // internal padding
...
panel.add(button[i], constraints);
Have a look at this tutorial: Laying Out Components Within a Container (The visual guide is a good start point)
EDIT:
you can also lay out the components by hand, that is, specify the location and size of each component in the container. For this you must set the LayoutManager to null so the default manager gets removed.
JPanel panel = new JPanel();
panel.setLayout(null);
...
button[i].setLocation(x, y);
button[i].setSize(width, heigth);
// OR button[i].setBounds(x, y, width, height);
panel.add(button[i]);

You need to define an appropriate LayoutManager for your JPanel, which is responsible for how the Components added to it are positioned. The default LayoutManager is FlowLayout, which lays out Components left-to-right. For laying out Components vertically you should consider using BoxLayout or GridBagLayout.

You have to set LayoutManager for JPanel or use Box(BoxLayout.Y_AXIS) instead.

For the size of buttons use preferredSize
For your layout problem you need to change the layout manager to one that does a vertical layout. For playing around purposes you can use BoxLayout like this:
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));

This is much easier if you let the layout manager do its work.
In Swing, the way the components are layout over other component ( a panel for instance ) is using a layout manager.
It is used to avoid having to compute the coordinates of all the components against each other each time the container component resizes, or a new component is added.
There are different layout mangers, the one that you need here is BoxLayout.
By using this layout you don't need to specify the button position, nor its size. The layout manager query each component and use that information to place them in the correct position and size.
For instance the following frame
Was created this ( modified version of your ) code:
import javax.swing.*;
import java.awt.*;
public class ScrollTest {
private JPanel panel;
private Icon[] icons = new Icon[3];
public void main() {
panel =new JPanel();
// Use top to bottom layout in a column
panel.setLayout( new BoxLayout( panel, BoxLayout.Y_AXIS ));
panel.setBackground(Color.WHITE);
int v=ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS;
int h=ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS;
JScrollPane jsp=new JScrollPane(panel,v,h);
jsp.setPreferredSize(new Dimension(600,600));
jsp.setBounds(150,670,850,200);
JFrame frame = new JFrame();
frame.add(jsp);
// my addition to load sample icons
loadImages();
// simulate dynamic buttons
addButtons();
frame.pack();
frame.setVisible( true );
}
void loadImages() {
icons[0] = new ImageIcon( "a.png" );
icons[1] = new ImageIcon( "b.png" );
icons[2] = new ImageIcon( "c.png" );
}
void addButtons() {
for( int i = 0 ; i < icons.length ; i++ ) {
JButton button = new JButton();
Icon icon = icons[i];
button.setIcon( icon );
// Set the button size to be the same as the icon size
// The preferred size is used by the layout manager
// to know what the component "better" size is.
button.setPreferredSize( new Dimension( icon.getIconWidth(),
icon.getIconHeight() ) );
// This is IMPORTANT. The maximum size is used bythe layout manager
// to know "how big" could this component be.
button.setMaximumSize( button.getPreferredSize() );
panel.add( button );
}
}
public static void main( String ... args ) {
new ScrollTest().main();
}
}
I hope this helps.

One can also get a vertical scrolling for JPanel with SpringLayout. It's possible if panel's vertical size will be defined by setting a constraint SpringLayout.SOUTH. This can be done like this:
JPanel panel = new JPanel();
SpringLayout panelLayout = new SpringLayout();
panel.setLayout(panelLayout);
// Adding components to the panel here
// .....
// That's what defines panel's exact size and makes its scrolling possible
panelLayout.putConstraint(SpringLayout.SOUTH, panel, 0,
SpringLayout.SOUTH, lastComponentOfThePanel);
JScrollPane panelScrollPane = new JScrollPane(panel);
where lastComponentOfThePanel is a component at the bottom of a panel.
Hope this will help somebody. In my opinion, SpringLayout is very powerful layout manager, and sometimes it's very difficult or almost impossible to replace this one with GridBagLayout.

What about?
JScrollPane scrollPane = new JScrollPane(yourpanel);
container.add(scrollPane);