Develop Reference

Items in GridBagLayout does not properly align

I'm trying to align 3 items in a GridBagLayout, 2 of the items being on top and 1 item at bottom. Both Items should be the same Size. I have tried to achieve this with BorderLayout and GridBagLayout but no luck.
This is my attempt with GridBagLayout as you can see they are not properly aligned. This is what I tried to do.
Add first item
Set the x to 1
Add second item
Set the y to 1
Add the last item
I was hoping this would work because It doesn't make sense to me why this would not work, Here is the code for it.
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = 0;
JTextField oldPkg = new JTextField();
container.add(oldPkg, gbc);
gbc.gridx = 1;
JTextField newPkg = new JTextField();
gbc.gridy = 1;
JTextField apkPath = new JTextField();
container.add(apkPath, gbc);
The result I want to achieve is
I have achieved it with FlowLayout but it doesn't resign packed when the frame is resized, and the bottom bar is a bit big.
How can I achieve this with GridBagLayout or any other layout so it remains the same on size changes?

Sometimes, you need to set back and try a different approach. Maybe starting with and piece of paper, where you can draw the layout and plot out the constraints.
This will lead you to understanding that apkPath needs to start at x of 0 and "span" two columns.
Currently apkPath is using the same x position as newPkg, you need to change it before using it again.
gbc.gridy = 1;
gbc.gridx = 0;
JTextField apkPath = new JTextField();
container.add(apkPath, gbc);
Okay, but now it's the same size as oldPkg, we need to tell GridBagLayout we want to span multiple columns
gbc.gridy = 1;
gbc.gridx = 0;
gbc.gridwidth = 2;
JTextField apkPath = new JTextField();
container.add(apkPath, gbc);
should now allow the textfield to flow over both columns
I might suggest having a look at How to Use GridBagLayout for more details

Slightly off topic:
Might I just suggest not bothering with 90% of the inbuilt layouts and just going with MigLayout.
There is a MigLayout core jar, and MigLayout swing jar. (Don't take the MigLayout SWT jar by mistake, and also don't use the SWT versions in the import statements).
I guess the licence is liberal. But, you can check whether it fits your needs.
http://www.miglayout.com/
(Just a happy user. Not affiliated)
This does a lot in just a few lines:
public class LayoutAnswer extends JFrame {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
LayoutAnswer window = new LayoutAnswer();
window.init();
window.pack();
window.setVisible(true);
window.setLocationRelativeTo(null);
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
});
}
private JPanel panel = new JPanel( new MigLayout("insets 10","[300::, grow][400::, grow]","[100:150:200][100:150:200]") );
private JLabel lbl1 = new JLabel("One");
private JLabel lbl2 = new JLabel("Two");
private JLabel lbl3 = new JLabel("Three");
public void init() {
add(panel, BorderLayout.CENTER);
panel.add(lbl1, "");
panel.add(lbl2, "wrap");
panel.add(lbl3, "span 2");
}
}

What settings should I use to resolve this GridBagLayout resizing issue?

I have been searching and trying ways to resolve the problems I encountered with GridBagLayout resizing but to no avail. The problems are:
I drag the bottom of the JDialog window down to make it taller; the search panel (above panel in the below screenshot) kept getting taller, just adding white space that it didn't need for its contents (I don't want this wasted space which takes height away from the scrolling table below it).
If I move the right side of the window to make it a bit narrower, the scroll panel becomes too short even though my screen and the window could have displayed its full height; a vertical scroll bar appears (I don't like the panels to scroll vertically, just horizontally.)
My JDialog that holds below components in the upper right portion uses below layout manager and constraints:
JPanel level 1 uses GridBagLayout Setting 1 (see below)
JScrollPane level 2 uses GridBagLayout Setting 1
JPanel level 3 uses GridBagLayout Setting 2
JPanel level 4 uses GridBagLayout Setting 2
JPanel level 5 uses GridBagLayout Setting 2
JPanel level 5 uses GridBagLayout Setting 2
GridBagLayout.GridBagConstraints (c)
Setting 1:
c.fill = GridBagConstraints.BOTH;
c.weightx = 99.0;
c.weighty = 99.0;
Setting 2:
c.fill = GridBagConstraints.NONE;
c.weightx = 1.0;
c.weighty = 1.0;
Originally, this is my JDialog if I don't use JScrollPane:
If I drag the window to make it bigger, the size of the JPanel (which was what I use before I used JScrollPane to make it scrollable horizontally) remains as it is. I want to achieve the same behavior, only that I want to make it horizontally scrollable.
What layout manager should I use to resolve this resizing problem? If I have to really use GridBagLayout, what constraints/settings should I use? I would highly appreciate any suggestion. Thank you!
UPDATE 1 ------------------------------------------------------
Kindly check sample code scenario below. Both scrollable panels (RED and BLUE) use GridBagConstraints.BOTH, weightx and weighty equal to 99.0. I want the red panel to have a height that is enough to contain the text field. I also want that when the dialog is dragged down to make the window bigger, the red panel's height remains the same. Please note that in the actual screen, both panels' number of contents may change (add/minus buttons exist), hence, setting of minimum panel size (for resizing) won't help. Kindly advise how I should go about this case. Thanks!
package cfr.view.search;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JDialog;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;
public class GBLSample extends JDialog {
private JPanel contentPane;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
GBLSample frame = new GBLSample();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public GBLSample() {
setBounds(100, 100, 350, 400);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
GridBagLayout gbl_contentPane = new GridBagLayout();
contentPane.setLayout(gbl_contentPane);
// RED PANEL ------------------------------------------------
JScrollPane sp1 = new JScrollPane();
GridBagConstraints gbc1 = new GridBagConstraints();
gbc1.fill = GridBagConstraints.BOTH;
gbc1.weightx = 99.0;
gbc1.weighty = 99.0;
contentPane.add(sp1, gbc1);
JPanel redPanel = new JPanel();
redPanel.setBackground(Color.RED);
JTextField field = new JTextField(20);
GridBagConstraints gbc2 = new GridBagConstraints();
gbc2.anchor = GridBagConstraints.PAGE_START;
gbc2.fill = GridBagConstraints.NONE;
contentPane.add(field, gbc2);
redPanel.add(field);
sp1.setViewportView(redPanel);
// BLUE PANEL ------------------------------------------------
JScrollPane sp2 = new JScrollPane();
GridBagConstraints gbc3 = new GridBagConstraints();
gbc3.fill = GridBagConstraints.BOTH;
gbc3.gridx = 0;
gbc3.gridy = 1;
gbc3.weightx = 99.0;
gbc3.weighty = 99.0;
contentPane.add(sp2, gbc3);
JPanel bluePanel = new JPanel();
bluePanel.setBackground(Color.BLUE);
sp2.setViewportView(bluePanel);
}
}
UPDATE 2 ------------------------------------------------------
Still have the same problem with the JPanel's sizing as #1 above.
Problem 1

try this code:
package test;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.border.EmptyBorder;
public class GridBagLayoutSample extends JFrame {
private JPanel contentPane;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
GridBagLayoutSample frame = new GridBagLayoutSample();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public GridBagLayoutSample() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
GridBagLayout gbl_contentPane = new GridBagLayout();
gbl_contentPane.columnWidths = new int[]{0, 0};
gbl_contentPane.rowHeights = new int[]{50, 0, 0};
//the 1.0 value in columnWeights let redPanel and scrollPane (that contain bleuPanel) grow horizontally
//the 1.0 value is in the first index so it affect the first column
//you still need to use a valid value for gbc_redPanel.fill and gbc_scrollPane.fill;
gbl_contentPane.columnWeights = new double[]{1.0, Double.MIN_VALUE};
//the 0.0 value of rowWeights => components in first row will not grow
//the 0.0 value of rowWeights => components in second row will grow
gbl_contentPane.rowWeights = new double[]{0.0, 1.0, Double.MIN_VALUE};
contentPane.setLayout(gbl_contentPane);
JPanel redPanel = new JPanel();
redPanel.setBackground(Color.RED);
GridBagConstraints gbc_redPanel = new GridBagConstraints();
gbc_redPanel.insets = new Insets(0, 0, 5, 0);
gbc_redPanel.fill = GridBagConstraints.BOTH;
gbc_redPanel.gridx = 0;
gbc_redPanel.gridy = 0;
contentPane.add(redPanel, gbc_redPanel);
JScrollPane scrollPane = new JScrollPane();
GridBagConstraints gbc_scrollPane = new GridBagConstraints();
gbc_scrollPane.fill = GridBagConstraints.BOTH;
gbc_scrollPane.gridx = 0;
gbc_scrollPane.gridy = 1;
contentPane.add(scrollPane, gbc_scrollPane);
JPanel bleuPanel = new JPanel();
bleuPanel.setBackground(Color.BLUE);
//scrollpane work with the preferred size of the component in the viewportView
//try to change this values
bleuPanel.setPreferredSize(new Dimension(400, 400));
scrollPane.setViewportView(bleuPanel);
}
}
add this to your code
gbl_contentPane.rowHeights = new int[]{40, 0, 0};
gbl_contentPane.rowWeights = new double[]{0.0,0.0, 1.0, Double.MIN_VALUE};
gbc1.gridx = 0;
gbc1.gridy = 0;
and remove this
gbc1.weightx = 99.0;
gbc1.weighty = 99.0;

Maybe a GridBagLayout might not be suited for your current UI, and a BorderLayout would work better? Put the red panel in BorderLayout.NORTH and put the blue panel in BorderLayout.CENTER. Components in the CENTER region will grow and shrink as you resize your dialog, and your red panel's preferredSize will be respected as you +/- items.

I have been searching and trying ways to resolve the problems I encountered with GridBagLayout resizing but to no avail.
Welcome to GridBagLayout.
First thing to note is that in
JPanel redPanel = new JPanel();
redPanel.setBackground(Color.RED);
JTextField field = new JTextField(20);
// GridBagConstraints gbc2 = new GridBagConstraints();
// gbc2.anchor = GridBagConstraints.PAGE_START;
// gbc2.fill = GridBagConstraints.NONE;
// contentPane.add(field, gbc2);
redPanel.add(field);
sp1.setViewportView(redPanel);
You are adding the text field to the content pane and then adding it again to the panel, which overrides your previous assignment (a component can only belong to one container). I commented out the lines which do nothing. The choice for how to lay out the text field in the red panel is completely different than the choice of how to lay out the red panel in the content pane.
I want the red panel to have a height that is enough to contain the text field.
That is taken care of by the layout manager. However, if you resize the window manually so that the panel will not have enough space, then scrollbars will appear provided that the panel is in a JScrollPane. You can try to #Override the getMinimumSize of the panel to its getPreferredSize, but not all layout managers respect it, I believe.
Regardless, I don't see why you need the scroll pane for the red panel at all.
I also want that when the dialog is dragged down to make the window bigger, the red panel's height remains the same.
Then you should set its weighty to 0.
Note: don't use underscores (_) in non-final variable names in accordance with the Java naming conventions (gbl_contentPane should be gblContentPane).
Edit
Here is an example of of dynamically changing the allocated size for the redPanel. I use BorderLayout for the content pane (also suggested by Dan O) for simplicity.
public class GBLSample extends JDialog {
private JPanel contentPane;
private JScrollPane redSP = new JScrollPane(new RedPanel());
public static void main(String[] args) {
EventQueue.invokeLater(() -> {
GBLSample frame = new GBLSample();
frame.setVisible(true);
});
}
private class RedPanel extends JPanel {
RedPanel() {
setLayout(new GridBagLayout());
setBackground(Color.RED);
GridBagConstraints c = new GridBagConstraints();
c.anchor = GridBagConstraints.FIRST_LINE_START;
add(new JTextField(10), c);
c.weightx = 1;
c.gridx = 1;
add(new JComboBox<>(), c);
c.weightx = 0;
c.gridx = 0;
add(new JComboBox<>(), c);
c.gridx = 1;
add(new JComboBox<>(), c);
c.weighty = 1;
c.gridx = 0;
c.gridy = 2;
add(new JButton("SSSS"), c);
}
#Override
public Dimension getPreferredSize() {
Dimension dim = super.getPreferredSize();
JScrollBar sb = redSP.getHorizontalScrollBar();
if (!sb.isShowing())
return dim;
return new Dimension(dim.width, dim.height + sb.getHeight());
}
}
public GBLSample() {
setBounds(100, 100, 350, 400);
contentPane = new JPanel(new BorderLayout());
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
// RED PANEL ------------------------------------------------
redSP.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_NEVER);
contentPane.add(redSP, BorderLayout.PAGE_START);
// BLUE PANEL ------------------------------------------------
JPanel bluePanel = new JPanel();
bluePanel.setBackground(Color.BLUE);
contentPane.add(new JScrollPane(bluePanel));
}
}
The idea is to add all extra space at the bottom of the panel by giving all the weight to a component on the bottom (and similarly can be done for the x axis with a right-most component). When the scrollbar is shown, the panel recalculates its height and adds the scrollbar's height to to itself (to the bottom most component), then the scrollbar does not hide anything.

Unfortunately, there was a bug in the system's overridden JPanel.getMinimumSize() that was causing my search panel to get squished out of existence. I was able to find a fix for it already without changing any setting with the system's customized layout manager. Still, thanks a lot for all your answers and help.

JScrollPane can resize smaller, but JTextArea does not

I have a window containing a JScrollArea, which contains a JPanel which contains a JTextArea. When I resize the window to make it larger, the layout updates perfectly, but if I make the window smaller, the JPanel does not shrink its contents. I attempted to add a ComponentListener on the JScrollArea to resize the JPanel based on the new size of the viewport, but this seems to defeat the purpose of the vertical scroll bar.
UPDATE: The idea here is that the JScrollArea will contain a JPanel (since it can only contain one component for its viewport), and within that JPanel I will be adding multiple JPanels containing components that describe processes that are running to the user. Since there could be any number of these processes running, I need to have some kind of scroll bar functionality available. Hence the component hierarchy I'm using below.
The desired behavior here is that the window can be resized larger or smaller and the text area will wrap its contents accordingly, and a vertical scroll bar will appear if the contents of the JPanel are larger vertically than the window. Any suggestions?
public class TestWindow extends JFrame {
JPanel scrollContentPanel;
JScrollPane scrollPane;
public TestWindow() {
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
JPanel mainPanel = new JPanel();
this.setContentPane(mainPanel);
GridBagLayout mainPanelLayout = new GridBagLayout();
mainPanel.setLayout(mainPanelLayout);
scrollContentPanel = new JPanel();
scrollPane = new JScrollPane();
scrollPane.setViewportView(scrollContentPanel);
scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
GridBagLayout scrollContentLayout = new GridBagLayout();
scrollContentPanel.setLayout(scrollContentLayout);
JPanel contentEntry = new JPanel();
GridBagConstraints contentEntryConstraints = new GridBagConstraints();
contentEntryConstraints.weightx = 1.0;
contentEntryConstraints.insets = new Insets(3, 3, 5, 3);
contentEntryConstraints.fill = GridBagConstraints.BOTH;
contentEntryConstraints.gridx = 0;
contentEntryConstraints.gridy = 1;
scrollContentPanel.add(contentEntry, contentEntryConstraints);
GridBagLayout contentEntryLayout = new GridBagLayout();
contentEntry.setLayout(contentEntryLayout);
JTextArea descTextArea = new JTextArea();
descTextArea.setEditable(false);
descTextArea.setFont(new Font("Dialog", Font.PLAIN, 11));
descTextArea.setText("This is a description of an arbitrary unspecified length that may easily span multiple lines without any breaks in-between. Therefore it is necessary that the description automatically wrap as appropriate.");
descTextArea.setLineWrap(true);
descTextArea.setWrapStyleWord(true);
GridBagConstraints descTextAreaConstraints = new GridBagConstraints();
descTextAreaConstraints.weightx = 1.0;
descTextAreaConstraints.weighty = 1.0;
descTextAreaConstraints.insets = new Insets(0, 0, 3, 0);
descTextAreaConstraints.fill = GridBagConstraints.BOTH;
descTextAreaConstraints.gridx = 0;
descTextAreaConstraints.gridy = 1;
descTextAreaConstraints.gridwidth = 2;
contentEntry.add(descTextArea, descTextAreaConstraints);
GridBagConstraints scrollPaneConstraints = new GridBagConstraints();
scrollPaneConstraints.insets = new Insets(0, 0, 5, 0);
scrollPaneConstraints.weightx = 1.0;
scrollPaneConstraints.weighty = 1.0;
scrollPaneConstraints.fill = GridBagConstraints.BOTH;
scrollPaneConstraints.gridx = 0;
scrollPaneConstraints.gridy = 0;
mainPanel.add(scrollPane, scrollPaneConstraints);
scrollPane.addComponentListener(new ComponentAdapter() {
#Override
public void componentResized(ComponentEvent evt) {
super.componentResized(evt);
scrollContentPanel.setPreferredSize(scrollPane.getViewportBorderBounds().getSize());
scrollContentPanel.validate();
}
});
pack();
}
public static void main(String[] args) {
TestWindow wnd = new TestWindow();
wnd.setVisible(true);
}
}

JTextArea should be placed directly into the JScrollPane, as long as that is the component your are trying to scroll. If there are other items you want to scroll with it (and hence the intermediate JPanel), then you might want to consider making that JPanel implement Scrollable so that the JScrollPane knows what to do with it. JTextArea implements Scrollable, which is why it works with JScrollPane out of the box.

no idea about your goal without detailed description, explanation
JTextArea should be placed in JScrollPane
set intial setPreferredSize for JTextArea, e.g. JTextArea(5, 10)
you are put three JPanels (is there reason ??? for this components hierarchy) one to JScrollPane, JTextArea is placed directly into JPanel instead of to the JScrollPane
then usage of ComponentListener is useless and contraproductive

Java Swing GridBagLayout Component Positioning

I am using Swing's GridBagLayout for the fist time and I have so far only added two components to a container, although I intend to add more below vertically. So far, the first component (a JLabel) is positioned correctly at PAGE_START, and I have remembered to set weight attributes for the components' corresponding GridBagConstraints. The second component (a JTextField) however is not positioning as I intended and it being centered in the container rather than moving up underneath the JLabel. I have attempted to use multiple anchor constants including FIRST_LINE_START, PAGE_START, NORTH & NORTHWEST but so far nothing is working.
And so, once again I call for the gifted coders of stackoverflow for help. Below is a snippet of the code and below that is an image of the problem graphically.
// Instantiate components and configure their corresponding GridBagConstraints attributes
// refPlusType properties
refPlusType = new JLabel("<html><h3>"+"Reference"+" - "+"Job Type"+" </h3><hr /></html>");
refPlusTypeGC = new GridBagConstraints();
refPlusTypeGC.gridx = 0; // Grid position
refPlusTypeGC.gridy = 0;
refPlusTypeGC.gridwidth = 2; // Number of colums occupied by component
refPlusTypeGC.insets = new Insets(5, 10, 5, 10); // Specifies margin
refPlusTypeGC.weightx = 0.1; // Required for anchor to work.
refPlusTypeGC.weighty = 0.1; // Required for anchor to work.
refPlusTypeGC.anchor = GridBagConstraints.PAGE_START; // Position in container
// addressLine1 properties
addressLine1 = new JTextField();
addressLine1GC = new GridBagConstraints();
addressLine1GC.gridx = 0;
addressLine1GC.gridy = 1;
addressLine1GC.gridwidth = 2;
addressLine1GC.insets = new Insets(0, 10, 0, 10);
addressLine1GC.fill = GridBagConstraints.HORIZONTAL; // Specifies component fill Horizontal space
addressLine1GC.weightx = 0.1;
addressLine1GC.weighty = 0.1;
addressLine1GC.anchor = GridBagConstraints.FIRST_LINE_START;
// Add components to this HALLogisticsDetailsPanel
this.add(refPlusType, refPlusTypeGC);
this.add(addressLine1, addressLine1GC);
Image below;
Thank you all for any help you can offer.

Try increasing the weighty for addressLine1 to a much larger value. I did a quick test setting it to 1000:
addressLine1GC.weighty = 1000.0;
and that pushed the addressLine1 field up under the label with the whitespace below.

anchor = NORTH works like a charm:
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class TestJPanels {
private JLabel refPlusType;
private JTextField addressLine1;
protected void initUI() {
final JFrame frame = new JFrame(TestJPanels.class.getSimpleName());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel(new GridBagLayout());
// Instantiate components and configure their corresponding GridBagConstraints attributes
// refPlusType properties
refPlusType = new JLabel("<html><h3>" + "Reference" + " - " + "Job Type" + " </h3><hr /></html>");
GridBagConstraints refPlusTypeGC = new GridBagConstraints();
refPlusTypeGC.gridwidth = GridBagConstraints.REMAINDER; // Number of colums occupied by component
refPlusTypeGC.insets = new Insets(5, 10, 5, 10); // Specifies margin
refPlusTypeGC.weightx = 1; // Required for anchor to work.
refPlusTypeGC.anchor = GridBagConstraints.PAGE_START; // Position in container
// addressLine1 properties
addressLine1 = new JTextField(20);
GridBagConstraints addressLine1GC = new GridBagConstraints();
addressLine1GC.insets = new Insets(0, 10, 0, 10);
addressLine1GC.fill = GridBagConstraints.HORIZONTAL; // Specifies component fill Horizontal space
addressLine1GC.weightx = 1;
addressLine1GC.weighty = 1;
addressLine1GC.anchor = GridBagConstraints.NORTH;
// Add components to this HALLogisticsDetailsPanel
panel.add(refPlusType, refPlusTypeGC);
panel.add(addressLine1, addressLine1GC);
frame.add(panel);
frame.setSize(600, 600);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new TestJPanels().initUI();
}
});
}
}

The best 'tutorial' for GridBagLayout that I have seen was created by Scott Stanchfield. You can find a link to the PowerPoint presentation he gave at JavaOne 2001 here
There used to be an article online with the same information, but it appears to have been swallowed up by Oracle.
Please read all the warnings about why GBL is not ideal. If you are determined to use it, Scott gives a great visual lesson on how to determine all the constraints by creating a simple sketch of your GUI.
Jim S.

Okay, I got it. I don't like accepting my own answers but here we go. At the end of the day I am trying to get the whole lot to bunch together properly at the top of the container. Adding weighty attributes to all the components individually means that the remaining space in the container is distributed between all of them (relative to their weighty attribute) therefore spacing them out.
The answer seems to be that by adding a weighty attribute to the lowest component in the GridBagLayout, the rest of the remaining space is allocated to below the lowest component and therefore pushing all components to the top. By default is seems that when remaining space is allocated to a component based on it's weight, it is allocated below it (at least on the y axis).
Here is the new code with three components to help demonstrate;
// Instantiate components and configure their corresponding GridBagConstraints attributes
// refPlusType properties
refPlusType = new JLabel("<html><h3>"+"Reference"+" - "+"Job Type"+" </h3><hr /></html>");
refPlusTypeGC = new GridBagConstraints();
refPlusTypeGC.gridx = 0; // Grid position
refPlusTypeGC.gridy = 0;
refPlusTypeGC.gridwidth = 2; // Number of colums occupied by component
refPlusTypeGC.insets = new Insets(5, 10, 5, 10); // Specifies margin
// addressLine1 properties
addressLine1 = new JTextField();
addressLine1GC = new GridBagConstraints();
addressLine1GC.gridx = 0;
addressLine1GC.gridy = 1;
addressLine1GC.gridwidth = 2;
addressLine1GC.insets = new Insets(0, 10, 0, 10);
addressLine1GC.fill = GridBagConstraints.HORIZONTAL; // Specifies component fill Horizontal space
// addressLine2 properties
addressLine2 = new JTextField();
addressLine2GC = new GridBagConstraints();
addressLine2GC.gridx = 0;
addressLine2GC.gridy = 2;
addressLine2GC.gridwidth = 2;
addressLine2GC.insets = new Insets(0, 10, 0, 10);
addressLine2GC.fill = GridBagConstraints.HORIZONTAL; // Specifies component fill Horizontal space
addressLine2GC.weighty = 1; // Required for anchor to work.
addressLine2GC.anchor = GridBagConstraints.NORTH; // Position in container
// Add components to this HALLogisticsDetailsPanel
this.add(refPlusType, refPlusTypeGC);
this.add(addressLine1, addressLine1GC);
this.add(addressLine2, addressLine2GC);

How to use GridBagConstraints to create the layout?

I want to layout my JPane like so:
-------
| |
| |
| |
-------
| |
-------
This way, the top section is bigger/taller than the bottom section (the top section consists of another JPanel and uses the Graphics object to display an image, while the bottom section also consists of another JPanel but uses the Graphics object to draw some lines and text).
I've heard that the best way to do this was using the GridBagLayout and GridBagConstraints.
I'm trying to figure out the appropriate properties for the GridBagConstraints, and I'm having some difficulties. This is what I have so far...
For the top part, I have:
gridx = 0
gridy = 0
weighty = 1.0; // expand downwards, because the bottom should never expand in the Y direction
fill = GridBagConstraints.BOTH
For the bottom part, I have:
gridx = 0
gridy = 1
fill = GridBagConstraints.HORIZONTAL
anchor = GridBagConstraints.PAGE_END
Unfortunately, all the ends up happening is a large gray rectangle appears (I have a white background for the application) - no images load, no lines/text appear.
What should I do? What should I adjust?
I've read a few tutorials, but it just seems really confusing, I got it working in my first application, but now when I try to do this it just doesn't seem to work for me.

In general, for gridbag layout
if you want a component scale, you must give its scale direction a weight, and any sizes (width/height) you set for that direction will be ignored by the layout manager.
If you don't want a component scale, the component must have its size defined (if you want, you can dig into this topic in documents of java). In your case of the bottom panel, you need to give its, at least, a preferred height.
This can work as your expectation
pnlTop.setBackground(Color.WHITE);
pnlBottom.setBackground(Color.BLUE);
// Because you don't want the bottom panel scale, you need to give it a height.
// Because you want the bottom panel scale x, you can give it any width as the
// layout manager will ignore it.
pnlBottom.setPreferredSize(new Dimension(1, 20));
getContentPane().setLayout(new GridBagLayout());
GridBagConstraints cst = new GridBagConstraints();
cst.fill = GridBagConstraints.BOTH;
cst.gridx = 0;
cst.gridy = 0;
cst.weightx = 1.0; // --> You miss this for the top panel
cst.weighty = 1.0;
getContentPane().add(pnlTop, cst);
cst = new GridBagConstraints();
cst.fill = GridBagConstraints.HORIZONTAL;
cst.gridx = 0;
cst.gridy = 1;
cst.weightx = 1.0; // You miss this for the bottom panel
cst.weighty = 0.0;
getContentPane().add(pnlBottom, cst);
Further more, if you want to use gridbag layout, I recommend you to try the painless-gridbag library http://code.google.com/p/painless-gridbag/ (I'm the author of that library). It doesn't solve this problem for you (as your problem concerns managing component's size in gridbag layout) but it will save you a lot of typing and make your code easier to maintain
pnlBottom.setPreferredSize(new Dimension(1, 20));
PainlessGridBag gbl = new PainlessGridBag(getContentPane(), false);
gbl.row().cell(pnlTop).fillXY();
gbl.row().cell(pnlBottom).fillX();
gbl.done();

not sure from your question, maybe will help you Top at 70%, Bottom at 30%
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
public class BorderPanels extends JFrame {
private static final long serialVersionUID = 1L;
public BorderPanels() {
getContentPane().setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
JPanel panel1 = new JPanel();
Border eBorder = BorderFactory.createEtchedBorder();
panel1.setBorder(BorderFactory.createTitledBorder(eBorder, "70pct"));
gbc.gridx = gbc.gridy = 0;
gbc.gridwidth = gbc.gridheight = 1;
gbc.fill = GridBagConstraints.BOTH;
gbc.anchor = GridBagConstraints.NORTHWEST;
gbc.weightx = gbc.weighty = 70;
getContentPane().add(panel1, gbc);
JPanel panel2 = new JPanel();
panel2.setBorder(BorderFactory.createTitledBorder(eBorder, "30pct"));
gbc.gridy = 1;
gbc.weightx = 30;
gbc.weighty = 30;
gbc.insets = new Insets(2, 2, 2, 2);
getContentPane().add(panel2, gbc);
pack();
}
public static void main(String[] args) {
new BorderPanels().setVisible(true);
}
}

If you may use 3th party libs, you may consider the FormLayout as well. It allows you to specify the height of each row, and the resize behavior.
I did not test this but
FormLayout layout = new FormLayout(
"pref", //columns
"50dlu:grow(0.2)","25dlu:grow(0.1)" //rows
);
might do the trick. More information on the syntax can be found in the JGoodies Forms pdf