i'm playing with GridBagLayout in java, I wrote the following code but it's not working as I expected
I expected that the first button would be placed in point (0,0) which is upper left of the frame.
secondly, I expected that the second button height and width would be twice the size of the first button height and width but they weren't.
here is the output: https://ibb.co/hDZPgx
here is the code:
import javax.swing.*;
import java.awt.*;
public class GUIJframe extends JFrame {
private JButton jb1 = new JButton("first");
private JButton jb2 = new JButton("second");
private JButton jb3 = new JButton("third");
private GridBagConstraints gbc = new GridBagConstraints();
private GridBagLayout gbl = new GridBagLayout();
public GUIJframe () {
jcb.addItem(names);
setLocation(150,150);
setSize(500,500);
setLayout(gbl);
addComponent(jb1,0,0,1,1);
addComponent(jb2,1,0,2,2);
addComponent(jb3,2,2,5,5);
setVisible(true);
}
public void addComponent (Component component, int gridx,int gridy, int width, int height) {
gbc.gridx = gridx;
gbc.gridy = gridy;
gbc.gridwidth = width;
gbc.gridheight = height;
gbl.setConstraints(component,gbc);
add (component);
}
}
I expected that the second button height and width would be twice the size of the first button height and width
Your expectation is wrong.
GridBagLayout cells are flexible. The width of one column does not depend on the width of other columns. It only depends on the widths of child components in it (and the insets and ipadx, if set).
If a component takes up two columns, but there is nothing else in either of those columns, there is no reason for the GridBagLayout to expand the columns any larger than necessary to accommodate the preferred width of that component.
The same is true for heights and GridBagLayout rows.
To force one component to be twice the size of another, you will need a different layout. SpringLayout can do it, though it’s not easy to use. You might find it easier to simply add a ComponentListener on the “smaller” component, and use that component’s new size as the basis for the ”larger” component‘s preferred size.
To achieve your desired result, I would use SpringLayout.
SpringLayout lets you create constraints, called Springs, which represent sizing ranges for edges, widths, and heights of components. These can depend on the size ranges of other components, or edges of the container.
SpringLayout layout = new SpringLayout();
setLayout(layout);
SpringLayout.Constraints jb1Constraints =
new SpringLayout.Constraints(jb1);
SpringLayout.Constraints jb2Constraints =
new SpringLayout.Constraints(
Spring.sum(jb1Constraints.getX(), jb1Constraints.getWidth()),
jb1Constraints.getY(),
Spring.scale(jb1Constraints.getWidth(), 2),
Spring.scale(jb1Constraints.getHeight(), 2));
SpringLayout.Constraints jb3Constraints =
new SpringLayout.Constraints(
Spring.sum(jb2Constraints.getX(),
Spring.scale(jb2Constraints.getWidth(), 0.5f)),
Spring.sum(jb2Constraints.getY(), jb2Constraints.getHeight()),
Spring.scale(jb1Constraints.getWidth(), 5),
Spring.scale(jb1Constraints.getHeight(), 5));
add(jb1, jb1Constraints);
add(jb2, jb2Constraints);
add(jb3, jb3Constraints);
// Make container big enough to hold all components.
layout.putConstraint(
SpringLayout.EAST, getContentPane(), 0,
SpringLayout.EAST, jb3);
layout.putConstraint(
SpringLayout.SOUTH, getContentPane(), 0,
SpringLayout.SOUTH, jb3);
The constraints for jb1 are the easiest: honor that component’s minimum size, prefered size, and maximum size. Location is (0, 0).
The constraints for jb2 depend on those of jb1:
The Spring for the x coordinate of jb2 is jb1.x + jb1.width, which is effectively the right edge of jb1.
jb2 has the same y as jb1 (which is, in fact, zero).
The width and height are those of jb1, scaled by 2.
The constraints for jb3 depend on both jb2 and jb1:
The x coordinate is jb2.x + (jb2.width ÷ 2), that is, the horizontal center point of jb2.
The y coordinate is jb2.y + jb2.height, which is effectively the bottom edge of jb2.
The width and height are those of jb1, scaled by 5.
Finally, SpringLayout is different from other layout managers, in that it doesn’t automatically set the size of the container it’s laying out to be big enough to hold all child components. We have to do that work ourselves, by using SpringLayout.putConstraint to link the container’s right edge (EAST) to the jb3’s right edge, and the container’s bottom edge (SOUTH) to jb3’s bottom edge.
Related
The problem:
JPanel with GridBagLayout contains two JScrollPane components, the top one contains JTextArea, the bottom one contains JTable. I expect this set up to make the components fluidly fill the container JPanel and evenly share the vertical area of it on resizing. What actually happens is that the top JScrollPane component shrinks vertically on resizing giving more vertical area to the bottom JScrollPane component to invade; this happens at some sizes, I don not know if they are random.
Important notes:
I already applied GridBagConstraints#weighty = 0.5; to both components, which is supposed to do the job.
I noticed that the problem is because of the presence of the JTextArea, in that if I switch locations; make the JScrollPane/JTextArea on the bottom side and JScrollPane/JTable on the top side; the bottom component JScrollPane/JTextArea shrinks vertically giving more vertical area to the top component JScrollPane/JTable to invade.
I know this exact case can be solved simply using GridLayout(2,1) instead of GridBagLayout (or may be other solutions), however I am fan of GridBagLayout and I want to use most of it. Also if I want to add three components instead of two and I want to make them share the vertical area by percentage for example (%25, %25, 50%) I can use GridBagConstraints#weighty = (0.25, 0.25, 0.5) which is easily applicable with GridBagLayout.
So, in this case how to make components evenly share the vertical area of JPanel container with GridBagLayout on resizing?. Or, in other words; how to enforce components to respect GridBagConstraints#weighty = 0.5; setting on resizing which is applied to both?
Code in SSCCE format:
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextArea;
import javax.swing.table.DefaultTableModel;
public class GridBagFluidFill {
private static JPanel createFormPanel() {
JPanel containerPanel = new JPanel(new GridBagLayout());
containerPanel.setPreferredSize(new Dimension(350, 200));
JScrollPane scrollableTextArea;
JScrollPane scrollableTable;
JTextArea textArea = new JTextArea();
scrollableTextArea = new JScrollPane(textArea);
DefaultTableModel model = new DefaultTableModel(new String[]{"Column1", "Column2", "Column3"}, 0);
JTable table = new JTable(model);
scrollableTable = new JScrollPane(table);
GridBagConstraints c = new GridBagConstraints();
c.gridy = 0;
c.weightx = 1.0;
// I expect this to reserve 50% of the height all time.
c.weighty = 0.5;
c.fill = GridBagConstraints.BOTH;
c.anchor = GridBagConstraints.PAGE_START;
containerPanel.add(scrollableTextArea, c);
c = new GridBagConstraints();
c.gridy = 1;
c.weightx = 1.0;
// I expect this to reserve 50% of the height all time.
c.weighty = 0.5;
c.fill = GridBagConstraints.BOTH;
c.anchor = GridBagConstraints.PAGE_END;
containerPanel.add(scrollableTable, c);
return containerPanel;
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(() -> {
JPanel formPanel = createFormPanel();
JFrame frame = new JFrame("GridBagFluidFill");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(formPanel);
frame.pack();
frame.setVisible(true);
});
}
}
GridBagLayout is complex, and while its documentation does describe all of its functionality, some of it is easy to misinterpret.
I already applied GridBagConstraints#weighty = 0.5; to both components, which is supposed to do the job.
That is not what weightx and weighty do.
Equal weightx and weighty values do not coerce components into having the same width or height. The weight values determine the distribution of extra space when a container is larger than the preferred sizes of each component.
Here is a program which demonstrates this:
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.GridBagConstraints;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JPanel;
import javax.swing.JFrame;
public class GridBagEqualWeightsDemo {
static void showWindow() {
// Source: https://www.gutenberg.org/files/98/98-h/98-h.htm
String text =
"It was the best of times, it was the worst of times, it was"
+ " the age of wisdom, it was the age of foolishness, it was the"
+ " epoch of belief, it was the epoch of incredulity, it was the"
+ " season of Light, it was the season of Darkness, it was the"
+ " spring of hope, it was the winter of despair, we had everything"
+ " before us, we had nothing before us, we were all going direct"
+ " to Heaven, we were all going direct the other way—in short,"
+ " the period was so far like the present period, that some of its"
+ " noisiest authorities insisted on its being received, for good"
+ " or for evil, in the superlative degree of comparison only.";
JTextArea topArea = new JTextArea(text, 4, 20);
topArea.setLineWrap(true);
topArea.setWrapStyleWord(true);
JTextArea bottomArea = new JTextArea(text, 8, 20);
bottomArea.setLineWrap(true);
bottomArea.setWrapStyleWord(true);
JScrollPane top = new JScrollPane(topArea);
JScrollPane bottom = new JScrollPane(bottomArea);
top.setMinimumSize(top.getPreferredSize());
bottom.setMinimumSize(bottom.getPreferredSize());
JPanel panel = new JPanel(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.fill = GridBagConstraints.BOTH;
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.weightx = 1;
gbc.weighty = 0.5;
panel.add(top, gbc);
panel.add(bottom, gbc);
JFrame frame = new JFrame("GridBagConstraints Equal Weights");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(panel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> showWindow());
}
}
As you can see, the two components start out with different preferred heights, so GridBagLayout will never give them the same height. As you make the window taller, the components’ respective heights look more similar due to the smaller relative difference, but they are never the same.
GridBagLayout only uses the weighty to determine how to distribute the extra space—that is, the container height which exceeds each component’s (different) preferred height. If the panel is 50 pixels higher than the preferred height, as computed based on each child component’s preferred size, then equal weighty values means each component will be laid out with 25 pixels added to its respective preferred height.
If you want to force two components which may have different preferred sizes to always have the same width and/or height, GridBagLayout is the wrong tool for the job. As you have mentioned, GridLayout is well suited to this. SpringLayout can also do this, though its usage is complex.
You are free (and encouraged!) to use multiple panels inside each other with different layouts.
I already applied GridBagConstraints#weighty = 0.5; to both components, which is supposed to do the job.
The weighty constraint is used to tell the GridBagLayout how to allocate "extra" (and apparently less) space.
That is, each component is first allocated its preferred space. Then if there is extra (or apparently less) space available, that constraint is used.
If you add debug code to display the preferred sizes of each scroll pane you will get:
java.awt.Dimension[width=223,height=19] // text area
java.awt.Dimension[width=453,height=403] // table
So the issue is with this statement:
containerPanel.setPreferredSize(new Dimension(350, 200));
You are forcing the components to be smaller than their preferred size. So it appears the GridBagLayout is allocating 50% to each.
I was wondering why JTextArea shrinks without a good reason
As the height of the frame grows each component is allocated 50% until the point at which the frame is large enough to display each component at its preferred size. This is why the text area shrinks and the table jumps.
As you increase the height from there extra space is allocated at 50/50 as expected.
If you uncomment the setPreferredSize() statement you will see the natural layout and the reason for the jumping becomes clear.
I want to make them share the vertical area by percentage for example (%25, %25, 50%)
If you want allocations like that then check out Relative Layout which was designed for this purpose.
I'm using a GridBagLayout Manager to define clearly where (for now) thow labels and a JScrollPane should be.
I use gridbagconstraint to tell the first JLabel named "label1" (with text) he should be 3 unit wide * 1 units tall.
I tell another JLabel named "blank" (empty) he should be 9 units wide * 1 unit tall.
Then I declare a JScrollPane, and tell it it should be on y=1, height = 11, and x=0 width = 12.
I set gridbag's contraint's fill to BOTH, because want each component to fill the rectangle I describe.
label1 should be a quarter of the whole width available, but since label1 has some text, label1 takes 2/3 of the space.
Is there a way to just ignore the PreferredSizes of the components, just like a GridLayout (kind of) does ?
I've read the documentation about this, but I don't find any clue.
Some source code :
public class JPanelMain {
//gridconstraints
private GridBagConstraints gbc;
private static final int min = 1;
private static final int maxSize= 12;
private static final int forth =maxSize/4;
private static final int third =maxSize/3;
public JPanelMain(JFrame frame) {
JPanel pane = new JPanel();
pane.setLayout(new GridBagLayout());
gbc = new GridBagConstraints(
0,//gridx
0,//gridy
0,//gridwidth
0,//gridheight
1,//weightx
1,//weighty
GridBagConstraints.CENTER,//anchor
GridBagConstraints.BOTH,//fill
new Insets(0,0,0,0),//insets
0,//padx
0//pady
);
JLabel label1 = new JLabel ();
label1.setBorder(BorderFactory.createTitledBorder("Label1"));
JLabel blank = new JLabel();
blank.setBorder(BorderFactory.createTitledBorder("blank"));
label1.setOpaque(true);
gbc.gridwidth =(third);
gbc.gridheight = (min);
pane.add(label1,gbc);
label1.setText("Label1");
blank.setOpaque(true);
gbc.gridx = third;
gbc.gridwidth = maxSize -third;
pane.add(blank,gbc);
gbc.gridy = min;
gbc.gridheight = maxSize - min;
gbc.gridx= 0;
gbc.gridwidth=maxSize;
DefaultListModel<String> patients = new DefaultListModel<>();
fill(patients);
JList<String> list = new JList<>(patients);
pane.add(new JScrollPane(list),gbc);
frame.add(pane);
}
private void fill (DefaultListModel<String> model) {
/**/
}
}
the result is as described (and it is the same in height):
I've read (and I believe mostly understood) the example.
There is no such concept as "units" in GridBagLayout. A GBL uses cells.
If you have two components on the first row then you have two cells. Each cell is sized by the component in the cell.
If you then have a component on the second row you have a couple of options. The component could be displayed in the first or second column. Or you could give the component a "gridwidth" of 2, which means it will fill the width of the two columns.
You could use the "weightx" constraint. It indicates how space should be allocated to a component when extra space is available. So if one component could be .20 and the other .80. This is the best way to assign space proportionally however this is only for the "extra" spaces. Each component will originally be sized at its preferred size.
If you want truly relative sizes then you can use the Relative Layout. It allows you to specify the size of components relative to the total space available, so the preferred size can be ignored.
So you would need to create a panel using the RelativeLayout for the first row containing the two labels and then add that panel to the panel using the GridBagLayout.
JPanel grid = new JPanel();
GridLayout layout = new GridLayout (6,7,0,0);
grid.setLayout (layout);
slot = new ImageIcon ("");
for (int x = 0; x < 42; ++x)
{
slotbtn = new JButton(slot);
slotbtn.setContentAreaFilled (false);
//slotbtn.setBorderPainted (false);
slotbtn.setBorder (BorderFactory.createEmptyBorder (0,0,0,0));
slotbtn.setFocusPainted (false);
grid.add(slotbtn);
}
This is the output I get:
I am creating a 6x7 grid. The output I need is for there to be no space in between the rows and columns, everything should be compressed together. I tried pack and it didn't work. What am I doing wrong?
-- I tried FlowLayout but I had to resize the frame and I have other buttons on the frame so I don't think I'd prefer resizing it to make the buttons fit in their proper places.
-- I placed this JPanel inside another jpanel(which uses borderlayout and contains two other panels) and I placed it at the center, the two other panels North and South.
this issue because you divide the grid (the whole size of grid) to 7*6 so if you re-size the window you will see this gaps changed so if you wan't to remove this gab
calculate the size of the window (ex: width = 7* width of your image , hight = 6*hight of your mage)
or re-size your image
JButton employs a margin property to provide additional padding to the content area of the button, you could try using...
slotbtn.setMargin(new Insets(0, 0, 0, 0));
I would also try using something like slotbtn.setBorder(new LineBorder(Color.RED)); to determine if the spacing is from the button, icon or layout
GridLayout will also provide each cell with equal amount of space, based on the available space to the container, this means that the cell may increase beyond the size of the icon.
While a little more work, GridBagLayout would (if configured properly) honour the preferred size of each component.
Have a look at How to use GridBagLayout for more ideas.
I get no margins using your code, with any image I use. Check your image. And maybe post a runnable example replicating the problem. Maybe there's something going on you're not showing us. I'd start by checking the image for margins. Check it against this. If it still has margins, than its your image. Also, Don't set the size to anything! You may be stretching the panel unnecessarily, which will cause the gaps. Also if there an of your other panels are larger than the grip panel, it will also cause it to stretch. But take all your set(Xxx)sizes out and see what happens. Just pack()
import java.awt.GridLayout;
import javax.swing.*;
public class TestButtonGrid {
public TestButtonGrid() {
ImageIcon icon = new ImageIcon(getClass().getResource("/resources/stackoverflow3.png"));
JPanel panel = new JPanel(new GridLayout(6, 7));
for (int i = 0; i < 42; i++) {
JButton slotbtn = new JButton(icon);
slotbtn.setContentAreaFilled(false);
//slotbtn.setBorderPainted (false);
slotbtn.setBorder(BorderFactory.createEmptyBorder(0, 0, 0, 0));
slotbtn.setFocusPainted(false);
panel.add(slotbtn);
}
JFrame frame = new JFrame();
frame.add(panel);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
new TestButtonGrid();
}
}
I want to resize my buttons to be the same size and place then in a Panel on a JApplet. I have tried using
public void init() {
// TODO start asynchronous download of heavy resources
JButton btnWestern=new JButton("Western");
JButton btnPop=new JButton("Pop");
GridBagConstraints c4=new GridBagConstraints();
JPanel jPanel1 = new JPanel();
getContentPane().setLayout(new java.awt.GridBagLayout());
jPanel1.setLayout(new java.awt.GridBagLayout());
c4.gridx = 0;
c4.gridy = 0;
c4.insets = new Insets(36, 10, 0, 249);
jPanel1.add(btnWestern, c4);
c4.gridx = 0;
c4.gridy = 1;
c4.insets = new Insets(33, 10, 0, 249);
jPanel1.add(btnPop, c4);
add(jPanel1, new java.awt.GridBagConstraints());
}
When I run, this is what I get
But I noticed that if I change the button text to be the same or have the same length, like
JButton btnWestern=new JButton("Button1");
JButton btnPop=new JButton("Button2");
I get the desired output
What can I do to make sure that even the text of the buttons are not the same length, the buttons are the same size?
I'd suggest reading through the How to Use GridBagLayout tutorial if you haven't already. GridBagLayout is powerful but it is also one of the more complex LayoutManagers available.
I believe you need to set the GridBagConstraints.fill property to get the behavior you desire.
In your case this should be something like
c4.fill = GridBagConstraints.HORIZONTAL;
Edit (A bit of explanation for the observed behavior) When you use the same text on both buttons, their calculated size ends up being the same, so they are rendered as you want. When you use different size text, the buttons will render in a size that fits the text by default. The default value for GridBagConstraints.fill is GridBagConstraints.NONE which indicates to the LayoutManger to not resize the component. Changing the fill to GridBagConstraints.HORIZONTAL tells the LayoutManger to resize the component horizontally to fill the display area.
In the following GridBagLayout code, I'm expecting the specified minimum size of JButton btn2 to be respected when the JFrame is resized to be made smaller. But when I make the JFrame smaller, the btn2 gets smaller than its minimum size and then vanishes.
Can someone point me in the right direction of what I'm doing wrong? Maybe I have to set the minimum size of the JPanel that contains the buttons?
Any help is appreciated, thanks!
JFrame frame = new JFrame();
frame.setSize(400,300);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel();
panel.setMinimumSize(new Dimension(400,300));
panel.setBackground(Color.RED);
panel.setLayout(new GridBagLayout());
GridBagConstraints gbc = null;
JButton btn1 = new JButton("btn1");
btn1.setPreferredSize(new Dimension(150,50));
btn1.setMinimumSize(new Dimension(150,50));
gbc = new GridBagConstraints(0, 0, 1, 1, 0.0, 0.0,
GridBagConstraints.NORTHWEST, GridBagConstraints.NONE,
new Insets(0,0,0,0), 0, 0);
panel.add(btn1, gbc);
JButton btn2 = new JButton("btn2");
btn2.setPreferredSize(new Dimension(150,150));
btn2.setMinimumSize(new Dimension(150,150));
gbc = new GridBagConstraints(1, 0, 1, 1, 1.0, 1.0,
GridBagConstraints.NORTHWEST, GridBagConstraints.BOTH,
new Insets(0,0,100,100), 0, 0);
panel.add(btn2, gbc);
frame.getContentPane().add(panel);
frame.setVisible(true);
In addition to Andrew Thompson's answer:
The GBL DOES NOT respect the minimum size set on a component if the component's preferred size can and will be respected.
The GBL DOES respect the minimum size set on a component when the component's preferred size cannot be respected, that is: the component prefers to be of size (w,h) but the GBL sees this is impossible due to lack of space, and therefore it falls back on the advertised minimum size of the component.
It is therefore very much possible to make your component suddenly become larger than it was before when you downsize the containing frame. You only have to set a minimum size on it that is larger than the preferred size. So you are making the frame smaller, and suddenly your component becomes larger. That is... weird but possible :) All hail GBL.
Here is an example of a panel that implements this behavior (GBC is an easier class to use than the original GridBagConstraints):
private static JPanel getPanel() {
JPanel panel = new JPanel(new GridBagLayout());
final JTextField textField = new JTextField("test");
final String text = "text";
final JLabel label = new JLabel(text);
final JButton button = new JButton(new AbstractAction("Enlarge label!") {
private String actText = text;
#Override
public void actionPerformed(ActionEvent arg0) {
actText = actText + text;
label.setText(actText);
}
});
GBC g;
g = new GBC().locate(0, 0).weight(0.0, 0.0).align(GBC.WEST, GBC.HORIZONTAL, null);
textField.setMinimumSize(new Dimension(200,20));
panel.add(textField, g);
g = new GBC().locate(1, 0).weight(1.0, 0.0);
panel.add(label, g);
g = new GBC().locate(0, 1).weight(1.0, 1.0).span(2, 1);
panel.add(button, g);
return panel;
}
In general, I would say to not use components that must be fixed in size within a GBL. Wrap it inside other panels with different layout managers.
If you really want to use your fixed-sized component within a GBL, override its getPreferredSize() method and return the size you want. But I prefer to ignore these methods.
Maybe I have to set the minimum size of the JPanel that contains the buttons?
AFAIR GBL was notorious for ignoring sizing hints. No, a correction on that. To get sensible resizing of components within GBL, use the GridBagConstraints with appropriate values. Beware though, the behavior of the layout to not display any component that would be forced to less than its minimum size.
I would pack() the frame then set the minimum size on the frame. Here is how it might look, changing the last line to..
frame.pack();
frame.setVisible(true);
frame.setMinimumSize(frame.getSize());
Given the layout though, I would tend to put btn1 into the PAGE_START of the BorderLayout of a panel that is then added to the LINE_START of another BL. btn2 would go in the CENTER of the outer BL.