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Can't a Swing component be added to multiple containers?

I'm trying (testing something else) to add one JButton reference into two JPanels to test it, and it disappears from the first panel it was added to!

So, can't a Swing component be added to multiple containers?

Thank you in advance.

JPanel vs JFrame in Java

I am learning Java gui. The way I learned to create a windows is to inherit or Extend JFrame class and I good to as JFrame contains all the properties of a Window. Now If I want to add something to this window, I need to use add() method. But Today I came across JPanel which also creates a windows and we can add stuff by jpanelObjec.add().

What is the difference between the two methods? Are they somehow related?

Java: Difference between the setPreferredSize() and setSize() methods in components

Ok, I read the Java Documentation and I just can't figure out what is the main difference between those two methods. Sometimes I used setSize(), sometimes setPreferredSize(), sometimes one does what I want, sometimes the other.

So, what is the main difference between the two? Which one should I use for JFrames and JPanels?

Thanks

How to include custom panel with NetBeans GUI Builder?

I have written a class that extends JPanel. Is it possible to use this in the NetBeans GUI Builder and have it survive all of the automatic code generation?

I have used the customised code option in the GUI builder to instantiate the object as the new class, but it seems like the declaration can't be changed from JPanel, so only methods that I have overridden get called, I can't call new ones that are not present in JPanel.

Concerns about the function of JPanel: paintcomponent()

hello I'm new in java programming, and i need someone explaining me these lines of code:

 public class drawpanel extends JPanel
 {
     public void paintComponent(Graphics g)
     { 
         super.paintComponent(g);
         ...
     }
 }

I dont understand the line public void paintComponent(Graphics g): why do i have to declare that function like that if it's predefined in JPanel?

And this line super.paintComponent(g): I dont understand it at all. Thank you for your help.

Align text in JLabel to the right

I have a JPanel with some JLabel added with the add() method of JPanel. I want to align the JLabel to the right like the image below but I don't know how to do that. Any Idea? Thanks!

JPanel Drop Shadow

I have a JPanel element and I would like added a drop shadow to it, how can I add a nice faded drop shadow to the element? Do I need to use external libraries or is there something that is built in that I can use?

Example:

Java - Vertical "FlowLayout" with Horizontal Scrolling

As described in the title, I've been trying to set up sort of a vertical flow layout with horizontal scrolling. The components within the layout will be JLabels. Let me draw a picture:

+-------------------------+   <--- window
|Label1   Label4    Label7|
|Label2   Label5    Label8|   <--- labels
|Label3   Label6    Label9|
|<===============>========|   <--- scrollbar
+-------------------------+

Same window, expanded vertically

+--------------------------+   <--- window
|Label1   Label5    Label9 |
|Label2   Label6    Label10|   <--- labels
|Label3   Label7    Label11|
|Label4   Label8    Label12|
|<===================>=====|   <--- scrollbar
+--------------------------+

So, the labels would fill the available vertical space and then create a new column. Once the available horizontal space is exhausted, a horizontal scrollbar would appear.

A vertical scrollbar should not typically appear; however, it would be nice to have a vertical scrollbar if the vertical height of the window is unusually small.

Any help is greatly appreciated. I'm new to Java, so any additional explanation would be wonderful. Thanks!

Edit:

Based on the responses below, I am now working with: http://tips4java.wordpress.com/2008/11/06/wrap-layout/ and http://code.google.com/p/verticalflowlayout/

I have the WrapLayout extending VerticalFlowLayout as such:

package LogicSim;

import java.awt.*;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;

/**
 *  FlowLayout subclass that fully supports wrapping of components.
 */
public class VerticalWrapLayout extends VerticalFlowLayout
{
private Dimension preferredLayoutSize;

/**
* Constructs a new <code>WrapLayout</code> with a left
* alignment and a default 5-unit horizontal and vertical gap.
*/
public VerticalWrapLayout()
{
    super();
}

/**
* Constructs a new <code>FlowLayout</code> with the specified
* alignment and a default 5-unit horizontal and vertical gap.
* The value of the alignment argument must be one of
* <code>WrapLayout</code>, <code>WrapLayout</code>,
* or <code>WrapLayout</code>.
* @param align the alignment value
*/
public VerticalWrapLayout(int align)
{
    super(align);
}

/**
* Creates a new flow layout manager with the indicated alignment
* and the indicated horizontal and vertical gaps.
* <p>
* The value of the alignment argument must be one of
* <code>WrapLayout</code>, <code>WrapLayout</code>,
* or <code>WrapLayout</code>.
* @param align the alignment value
* @param hgap the horizontal gap between components
* @param vgap the vertical gap between components
*/
public VerticalWrapLayout(int align, int hgap, int vgap)
{
    super(align, hgap, vgap);
}

/**
* Returns the preferred dimensions for this layout given the
* <i>visible</i> components in the specified target container.
* @param target the component which needs to be laid out
* @return the preferred dimensions to lay out the
* subcomponents of the specified container
*/
@Override
public Dimension preferredLayoutSize(Container target)
{
    return layoutSize(target, true);
}

/**
* Returns the minimum dimensions needed to layout the <i>visible</i>
* components contained in the specified target container.
* @param target the component which needs to be laid out
* @return the minimum dimensions to lay out the
* subcomponents of the specified container
*/
@Override
public Dimension minimumLayoutSize(Container target)
{
    Dimension minimum = layoutSize(target, false);
    minimum.width -= (getHgap() + 1);
    return minimum;
}

/**
* Returns the minimum or preferred dimension needed to layout the target
* container.
*
* @param target target to get layout size for
* @param preferred should preferred size be calculated
* @return the dimension to layout the target container
*/
private Dimension layoutSize(Container target, boolean preferred)
{
        synchronized (target.getTreeLock())
        {
    //  Each row must fit with the width allocated to the containter.
    //  When the container width = 0, the preferred width of the container
    //  has not yet been calculated so lets ask for the maximum.

    int targetWidth = target.getSize().width;

    if (targetWidth == 0)
        targetWidth = Integer.MAX_VALUE;

    int hgap = getHgap();
    int vgap = getVgap();
    Insets insets = target.getInsets();
    int horizontalInsetsAndGap = insets.left + insets.right + (hgap * 2);
    int maxWidth = targetWidth - horizontalInsetsAndGap;

    //  Fit components into the allowed width

    Dimension dim = new Dimension(0, 0);
    int rowWidth = 0;
    int rowHeight = 0;

    int nmembers = target.getComponentCount();

    for (int i = 0; i < nmembers; i++)
    {
        Component m = target.getComponent(i);

        if (m.isVisible())
        {
            Dimension d = preferred ? m.getPreferredSize() : m.getMinimumSize();

            //  Can't add the component to current row. Start a new row.

            if (rowWidth + d.width > maxWidth)
            {
                addRow(dim, rowWidth, rowHeight);
                rowWidth = 0;
                rowHeight = 0;
            }

            //  Add a horizontal gap for all components after the first

            if (rowWidth != 0)
            {
                rowWidth += hgap;
            }

            rowWidth += d.width;
            rowHeight = Math.max(rowHeight, d.height);
        }
    }

    addRow(dim, rowWidth, rowHeight);

    dim.width += horizontalInsetsAndGap;
    dim.height += insets.top + insets.bottom + vgap * 2;

    //  When using a scroll pane or the DecoratedLookAndFeel we need to
    //  make sure the preferred size is less than the size of the
    //  target containter so shrinking the container size works
    //  correctly. Removing the horizontal gap is an easy way to do this.

    Container scrollPane = SwingUtilities.getAncestorOfClass(JScrollPane.class, target);

    if (scrollPane != null)
    {
        dim.width -= (hgap + 1);
    }

    return dim;
}
}

/*
 *  A new row has been completed. Use the dimensions of this row
 *  to update the preferred size for the container.
 *
 *  @param dim update the width and height when appropriate
 *  @param rowWidth the width of the row to add
 *  @param rowHeight the height of the row to add
 */
private void addRow(Dimension dim, int rowWidth, int rowHeight)
{
    dim.width = Math.max(dim.width, rowWidth);

    if (dim.height > 0)
    {
        dim.height += getVgap();
    }

    dim.height += rowHeight;
}
}

Here is my frame setup:

    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(300, 300);
    frame.setVisible(true);


    JPanel panel = new JPanel();
    panel.setLayout( new VerticalWrapLayout(0) );

    JScrollPane pane = new JScrollPane(panel);
    frame.add( pane, BorderLayout.CENTER );

    for (int i=0; i < 80; i++ ) {
        panel.add( new JLabel( "Label" + i ) );
    }

Now, this sets up the labels in vertical columns in the way that I'm after, but it still creates the vertical scroll bar. I'm pretty shaky when it comes to modifying the VerticalWrapLayout class. Also, I really don't understand how the JScrollPane interacts will these classes. Any suggestions on how to proceed?

Solved! Please see the answers below as well as my answer.

Difference between JPanel, JFrame, JComponent, and JApplet

im making a physics simulator for fun and i was looking up graphics tutorials when i tried to figure out the difference between all these J's. could somebody elaborate on them or perhaps provide a link to a helpful source?

How do I change JPanel inside a JFrame on the fly?

To put it simple, there's a simple java swing app that consists of JFrame with some components in it. One of the components is a JPanel that is meant to be replaced by another JPanel on user action.

So, what's the correct way of doing such a thing? I've tried

panel = new CustomJPanelWithComponentsOnIt();
parentFrameJPanelBelongsTo.pack();

but this won't work. What would you suggest?

How can I align all elements to the left in JPanel?

I would like to have all elements in my JPanel to be aligned to the left. I try to do it in the following way:

JPanel panel = new JPanel();
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
panel.setAlignmentX(Component.LEFT_ALIGNMENT);

As a result Java use left side of all elements as a position of the element and then put all elements in the center (not left part) of the JPanel.

JPanel Padding in Java

I have a formatting question for my Java swing application. It should be fairly straightforward, but I am having difficulty finding any aid (Every topic seems to be regarding removing any default padding in JPanel). The text in my various JPanels hug the sides and top, touching the colored borders: how can I add padding? Thank you.

Java :Add scroll into text area

How can i add the scroll bar to my text area. i have tried with this code but it's not working.

            middlePanel=new JPanel();
        middlePanel.setBorder(new TitledBorder(new EtchedBorder(), "Display Area"));

        // create the middle panel components

        display = new JTextArea(16, 58);
        display.setEditable(false); // set textArea non-editable
        scroll = new JScrollPane(display);
        scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

        //Add Textarea in to middle panel
        middlePanel.add(scroll);
        middlePanel.add(display);

Thanks

add controls vertically instead of horizontally using flow layout

I am adding checkboxes on JPanel in flowLayout the checkboxes are being added horizontally

i want to add checkboxes vertically on JPanel using what is the possible solution for it please suggest.

How to add an image to a JPanel?

I have a JPanel to which I'd like to add JPEG and PNG images that I generate on the fly.

All the examples I've seen so far in the Swing Tutorials, specially in the Swing examples use ImageIcons.

I'm generating these images as byte arrays, and they are usually larger than the common icon they use in the examples, at 640x480.

1. Is there any (performance or other) problem in using the ImageIcon class to display an image that size in a JPanel?
2. What's the usual way of doing it?
3. How to add an image to a JPanel without using the ImageIcon class?

Edit: A more careful examination of the tutorials and the API shows that you cannot add an ImageIcon directly to a JPanel. Instead, they achieve the same effect by setting the image as an icon of a JLabel. This just doesn't feel right...