I have a panel derived from JPanel. I have a custom control derived from JLabel. I am attempting to center this custom JLabel on my panel.
The only way I know to do this that will work is to use the a null layout (setLayout(null)) and then calculate the custom JLabel's setLocation() point so that it's in the right spot.
The custom JLabel is physically moved from one panel to this panel in this app and I believe the location previously set in setLocation is affecting things. However when I set it to (0,0) the component goes up into the upper left corner.
BorderLayout doesn't work because when only 1 component is provided and placed into BorderLayout.CENTER, the central section expands to fill all of the space.
An example I cut and pasted from another site used BoxLayout and component.setAlignmentX(Component.CENTER_ALIGNMENT). This didn't work either.
Another answer mentioned overriding the panel's getInset() function (I think that's what it was called), but that proved to be a dead end.
So far I'm working with a panel with a GridBagLayout layout and I include a GridBagConstraints object when I insert the custom JLabel into my panel. This is inefficient, though. Is there a better way to center the JLabel in my JPanel?
Set GridBagLayout for JPanel, put JLabel without any GridBagConstraints to the JPanel, JLabel will be centered
example
import java.awt.*;
import javax.swing.*;
public class CenteredJLabel {
private JFrame frame = new JFrame("Test");
private JPanel panel = new JPanel();
private JLabel label = new JLabel("CenteredJLabel");
public CenteredJLabel() {
panel.setLayout(new GridBagLayout());
panel.add(label);
panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.add(panel);
frame.setSize(400, 300);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
CenteredJLabel centeredJLabel = new CenteredJLabel();
}
});
}
}
Supose your JLabel is called label, then use:
label.setHorizontalAlignment(JLabel.CENTER);
Forget all the LayoutManagers in the Java Standard Library and use MigLayout. In my experience it's much easier to work with an usually does exactly what you expect it to do.
Here's how to accomplish what you're after using MigLayout.
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import net.miginfocom.swing.MigLayout;
public class Test
{
public static void main( String[] args )
{
JFrame frame = new JFrame( );
JPanel panel = new JPanel( );
// use MigLayout
panel.setLayout( new MigLayout( ) );
// add the panel to the frame
frame.add( panel );
// create the label
JLabel label = new JLabel( "Text" );
// give the label MigLayout constraints
panel.add( label, "push, align center" );
// show the frame
frame.setSize( 400, 400 );
frame.setVisible( true );
}
}
Most of that is just boilerplate. The key is the layout constraint: "push, align center":
align center tells MigLayout to place the JLabel in the center of its grid cell.
push tells MigLayout to expand the grid cell to fill available space.
BoxLayout is the way to go. If you set up a X_AXIS BoxLayout, try adding horizontal glues before and after the component:
panel.add(Box.createHorizontalGlue());
panel.add(label);
panel.add(Box.createHorizontalGlue());
I don't like the answers here.
I've never seen a valid use of a GridBagLayout ever in my career. Not saying there isn't one, just saying I haven't seen [a valid] one, and there might be correlation there. Moreover, adding a single JLabel to the middle of a Container might make it center for demonstrational purposes, but you're going to have a lot harder of a time later on if you try to continue to work with that over some other layouts.
I do like the suggestion about the BoxLayout, because that is actually a great way to do it. That said, that answer is only part of the puzzle, hence why I'm dredging up a 7 year old question.
My 'Answer'
Really there is no short answer to your question. There is an exact answer to your question based on what you asked, but StackOverflow is about a community learning from each other, and I suspect you're trying to learn how to use layouts in general (or you were 7 years ago) and telling you to type a combination of keys to do exactly your demo case is not going to teach you the answer.
I'm going to try not to explain any layouts that you can't web-search the answer for on your own (with a link to the Oracle tutorial at the end, because I think it explains the different layouts fairly well).
BoxLayout
BoxLayout is one way to do it, and there is already a code snippet to demo it above so I won't provide one. I'll expand on it to say that, just as mentioned, that only answers your question exactly, but doesn't really teach you anything. Glue, as the BoxLayout refers to it, basically gives you an equal amount of remaining real-estate between all the 'glue' currently in the Container. So, if you were to do something like
panel.add(Box.createHorizontalGlue());
panel.add(label);
panel.add(Box.createHorizontalGlue());
panel.add(otherLabel);
You would find that your JLabel is no longer centered, because the 'glue' is only the remaining real-estate left, after two JLabels were added to the Container which will be equally divided between the two 'slots' (two calls to Container#add(Component) with a glue parameter) in theContainer`.
BorderLayout
BorderLayout is another way to go about this. BorderLayout is broken down into 5 regions. BorderLayout#CENTER, as you might guess, is the center region. The important note about this layout and how it centers things is how it obeys sizes of the Component that is in the center. That I won't detail though; the Oracle tutorial at the end covers it well enough if you're interested, I think.
Worth Noting
I suppose you could use a GridLayout, but it's a more simple way to do it over a GridBagLayout, which I already said even that I think is not a good approach. So I won't detail this one either.
The Point of it All
Now all that said, I think all LayoutManagers are worth a look. Just like anything else with relation to programming - use the tool that fits the job. Don't just assume because you used X layout before, that you should always use X layout and no other layout is viable. Figure out what you want your display to look like, and how you think it should behave with respect to resizing components, and then pick what you think would work best.
Another dual meaning of picking the right tool, is that you don't have to just fit all of your components into one single Container and make one layout do everything. There is nothing stopping you (and I strongly encourage you to) use multiple Containers and group them all together. Control each Container with a layout that is appropriate for that section of the display, and a different layout for a different Container.
Important!!
The reason why this is very important is because each layout has rules and things that they obey, and other things that they respect, and then others that are effectively ignored (i.e. preferred, maximum, and minimum sizes, for instance). If you use different layouts [correctly], you will find your display accepts dynamically being resized while still obeying the shape that you wanted it to hold. This is a very important key difference between doing it the right way, and just settling with GridBagLayout.
JPanel outer = new JPanel(new BorderLayout());
JPanel centerPanel = new JPanel();
centerPanel.setLayout(new BoxLayout(centerPanel, BoxLayout.PAGE_AXIS));
JPanel southPanel = new JPanel(new CardLayout());
outer.add(centerPanel, BorderLayout.CENTER);
outer.add(southPanel, BorderLayout.SOUTH);
Figure out what is appropriate to your scenario, and go with that. There is no one-size-fits-all unless you want something overly cumbersome and made redundant by other layouts (i.e. GridBagLayout).
Oracle's Tutorial
If you've made it this far, then I think you're looking for as much information as you can get. In which case, I strongly encourage you to read Oracle's tutorial on layout managers because it lays out general details of them all very well: https://docs.oracle.com/javase/tutorial/uiswing/layout/visual.html
Use this.
labelName.setHorizontalAlignment(SwingConstants.CENTER);
or
labelName.setHorizontalAlignment(JPanel.CENTER);
Both of them must work.
Do like this instead of libraries and layouts :
JLabel jlabel = new JLabel("Label Text", SwingConstants.CENTER);
Make sure to import javax.swing.SwingConstants INTERFACE , BUT DO NOT IMPLEMENT IT. It contains only constants and no methods.
Put the JLabel in a JPanel or else it will come at the center of the JFrame or JWindow (your top level container).
Related
I have a project to copy the google sign-in GUI here . So far I'm still searching on what I'm gonna start with, but after some research I think it is possible on BorderLayout to do this. Im getting how it works by readjusting everything through borders, and I kind of like it because it is quite responsive compared to having null layout and coding every setBounds for each component.
I've been imagining using a background panel, a panel for the fill up form,
and creating panels for each pair of label and textfields to properly create the space and stacking (or nesting) them on top of the other. Our teacher just told us to snip out the image, she just wants if we know how to design something out of scratch. That and also saving the input into a text file.
However, I can't seem to grasp the concept of increasing the component size inside the borders to imitate the gaps between the text fields, like some sort of a padding between components? Using setSize doesnt work and so far my search only results into resizing borders, or perhaps I still have not entered the right searachable term for it?
Also, Ive been looking for another way and I think this project will also work using GridBaglayout. However many people say GridBagLayout is too complicated. What do you think would be easier?
In my experience almost every (99%) of the panels using GridBagLayout can be designed by using all other layouts. So, someone could say that GridBagLayout is optional
In your situation, avoiding the use of a GridBagLayout is easy. Take a look at the following code:
public class NoGridBagLayout extends JFrame {
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> new NoGridBagLayout().setVisible(true));
}
public NoGridBagLayout() {
super();
setDefaultCloseOperation(EXIT_ON_CLOSE);
setExtendedState(MAXIMIZED_BOTH);
JPanel borderPanel = new JPanel(new BorderLayout());
borderPanel.setBorder(new TitledBorder("borderPanel - BorderLayout"));
JLabel label = new JLabel("Create a google account.");
label.setHorizontalAlignment(JLabel.CENTER);
label.setFont(label.getFont().deriveFont(25f));
borderPanel.add(label, BorderLayout.PAGE_START);
setContentPane(borderPanel);
JPanel gridPanel = new JPanel(new GridLayout(1, 2));
gridPanel.setBorder(new TitledBorder("gridPanel - GridLayout"));
getContentPane().add(gridPanel, BorderLayout.CENTER);
JPanel leftBoxedPanel = new JPanel(); // Fill it with panels using BoxLayout.X_AXIS
leftBoxedPanel.setLayout(new BoxLayout(leftBoxedPanel, BoxLayout.Y_AXIS));
leftBoxedPanel.setBorder(new TitledBorder("leftBoxedPanel - BoxLayout.Y_AXIS"));
gridPanel.add(leftBoxedPanel);
JPanel rightBoxedPanel = new JPanel(); // Fill it with panels using BoxLayout.X_AXIS
rightBoxedPanel.setLayout(new BoxLayout(rightBoxedPanel, BoxLayout.Y_AXIS));
rightBoxedPanel.setBorder(new TitledBorder("rightBoxedPanel - BoxLayout.Y_AXIS"));
gridPanel.add(rightBoxedPanel);
}
}
Preview:
I'am using panel with absolute layout (don't ask why) and I need to add elements on it programmatically. I done that part, but now I want to surround panel with JScrollPane so that when user add more items, scroll bar does its job. But surrounding panel with scroll bar doesn't work. What can I do here.
JFrame frame = new JFrame();
frame.setSize(582, 451);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
JScrollPane scrollPane = new JScrollPane();
scrollPane.setBounds(10, 11, 546, 391);
frame.getContentPane().add(scrollPane);
JPanel panel = new JPanel();
scrollPane.setViewportView(panel);
panel.setLayout(null);
for(int i=0;i<labelList.size();i++){
if(a==4){
a=0;
b++;
}
labelList.get(i).setBounds(10+120*a+10*a, 10+130*b+10*b, 120, 130);
labelList.get(i).setOpaque(true);
labelList.get(i).setBackground(Color.WHITE);
labelList.get(i).setText(Integer.toString(i));
panel.add(labelList.get(i));
a++;
}
You're not going to like my answer, but I feel that we should be compelled to give you the best answer, which is not always what you want to hear. And that is this: use layout managers to do your component layouts. Yes while it might seem to newbies that null layouts are the easiest to use, as you gain more experience you will find that exactly the opposite is true. Null layout use makes for very inflexible GUI's that while they might look good on one platform look terrible on most other platforms or screen resolutions and that are very difficult to update and maintain. Instead you will want to study and learn the layout managers and then nest JPanels, each using its own layout manager to create pleasing and complex GUI's that look good on all OS's.
As for ease of use, I invite you to create a complex GUI with your null layout, and then later try to add a component in the middle of this GUI. This will require you to manually re-calculate all the positions and sizes of components added to the left or below the new component, which is prone to many errors. The layout managers will all do this automatically for you.
Specifically use of valid layout managers will update your JPanel's preferredSize automatically increase as more components are added and as the JPanel is revalidated (the layouts are told to re-layout their components). Your null JPanel will not do this, and so the JScrollPane will not work. Yes, a work around is for you to manually calculate and set your JPanel's preferredSize, but this is dangerous and not recommended for the same reasons noted above.
I am extremely new to Java Swing, and I'm having quite a bit of issues getting a nice layout going. I have checked out google, and even other answers on this website, but no information I find seems to solve the issue. Here is the result of my efforts:
As you can see, the label, text field, and button are all out of alignment. It is my goal for all of them to have the same left-hand border, and for the button and text field to have the same right-hand border, with these left and right hand borders being each the same distance from the left and righthand sides of my window.
Here are the important parts of my code:
public void run()
{
JFrame frame = new JFrame("Arduino Server");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
InstancePanel = new ServerGUIPanel();
frame.getContentPane().add(InstancePanel);
frame.pack();
frame.setVisible(true);
}
And, in ServerGUIPanel.java:
public ServerGUIPanel()
{
setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
setPreferredSize(new Dimension(500, 500));
setBorder(new EmptyBorder(10, 10, 10, 10));
StatusLabel = new JLabel("STATUS: BOOTUP");
add(StatusLabel);
PortField = new JTextField();
PortField.setPreferredSize(new Dimension(5000, 20));
PortField.setMaximumSize(PortField.getPreferredSize());
PortField.setActionCommand("PortChanged");
add(PortField);
ConnectionButton = new JButton();
ConnectionButton.setPreferredSize(new Dimension(5000, 20));
ConnectionButton.setMaximumSize(ConnectionButton.getPreferredSize());
ConnectionButton.setActionCommand("ConnectionClicked");
add(ConnectionButton);
}
Does anyone have a simple solution to this? What am I doing wrong here?
Thank you very much!
--Georges Oates Larsen
Read the section from the Swing tutorial on How to Use BoxLayout for the basics of using a BoxLayout as well as a section on alignment issues.
Basically you need to make sure the alignmentX value of all components is set to be left aligned.
Also:
Don't use setPreferredSize() to set the size of a component. Each Swing component will determine its own preferred size.
Use Java naming conventions. Variable names should NOT start with an upper case character.
I would not recommend using setPreferredSize() AND setMaximumSize(). The latter will cause problems when stretching your main frame. [Your components will likely not want resize]
You should be using layout managers to handle all the alignments itself. I would stay away from using BoxLayout in this case, as different components want to size differently, and that will sway the alignment when added into your BoxLayout panel.
Moreover, you might want to give your main frame a layout as well.
Can you post how you used your GridBagLayout?
I think I solved my problem, but I don't know why it works this way, so I'm hoping someone can explain it to me so I don't do the same mistake again in the future.
Here's a quick example that is compilable of what I'm trying to do:
public class BoxLayoutTest extends JFrame
{
public BoxLayoutTest()
{
setSize(400,300);
JPanel mainPanel = new JPanel(new FlowLayout());
setContentPane(mainPanel);
JPanel subPanel = new JPanel();
subPanel.setLayout(new BoxLayout(subPanel, BoxLayout.PAGE_AXIS));
subPanel.setBackground(Color.BLUE);
JLabel labelTest = new JLabel("This is a test");
subPanel.add(labelTest);
labelTest.setPreferredSize(new Dimension(150, 20));
mainPanel.add(subPanel);
System.out.println(mainPanel.getSize());
}
public static void main( String[] args )
{
BoxLayoutTest testFrame = new BoxLayoutTest();
testFrame.setVisible(true);
}
}
At first, I had problems with the panel containing the JLabel not resizing like it should with the preferred size. I found out that it was because I was using some variation of mainPanel.getSize() as a preferred size for my subpanels. In this example, I'm using actual number values, which work.
The reason why it didn't work the old way (and that's actually the thing I'd like someone to explain), is why, as seen in the SOP line, mainPanel.getSize() returns a width and a height of 0 while it clearly takes the whole screen, which is 400x300.
Thanks #camickr for telling me I shouldn't set a preferredSize for my Panels, this helped me figure out where the problem was coming from.
Why [does] mainPanel.getSize() returns a width and a height of 0?
Until pack() "causes this Window to be sized to fit the preferred size and layouts of its subcomponents," the dimensions will be zero.
System.out.println(mainPanel.getSize());
this.pack();
System.out.println(mainPanel.getSize());
Console:
java.awt.Dimension[width=0,height=0]
java.awt.Dimension[width=160,height=30]
Its hard to say why your code doesn't work, since you didn't post your code. A few random lines of code does not give us the context of how the code is used in your program.
When you post a question you need to post your SSCCE which demonstrates the problem.
The glue should not have fixed the problem. The panel should still display, its just that it may not display in the position you expect it to be. A BoxLayout will attempt to resize components added to it to fill up the entire space available to it.
You should not be using setPreferredSize() on a panel. It is the job of the layout manager to calculate the preferred size of the panel based on the preferred size of all the components added to it. So I would say your code is still wrong.
is there a difference between typing this and this.getContentPane()
Certain methods calls are automatically forwarded to the content pane of the frame, which is why the end result is the same. Read the JFrame API. This is addressed in the API description or for the method in question.
I'm trying to create a JDialog like the Symbol dialog in Microsoft Word that you get by choosing Symbol... from the Insert menu. Basically, it's an n x m (n and m are not known until runtime) grid of small buttons. I've got a first version of this working nicely using a GridLayout. The problem is that when you resize the dialog (and there is a requirement that you should be able to resize it), the size of the buttons changes. I need the size of the buttons to remain constant.
But I want the dimensions of the grid containing the buttons to change. For example, if the dialog gets wider, but stays the same height, the number of rows should lessen, while the number of columns increases.
I've thought of a couple of ways to fix this:
When the dialog is resized, create a new GridLayout and repopulate it with the buttons. I'm going to try this and see how it looks, but it seems like a clumsy way of doing it.
Use some other type of layout such as a FlowLayout. I took a stab at this, but it put all n x m buttons in one row. I do not want to use horizontal scroll-bars and the buttons ran off the right edge. Anyway, it's supposed to be a 2-dimensional grid of buttons.
What is the best way to solve this layout problem?
Create a buttons panel with GridLayout and set a fixed size (could be calculated at runtime of course) to it. The buttons panel should be contained in a panel of BoxLayout.
Check out the BoxLayout Tutorial
Very Very basic example:
public static void main(String[] args) throws Exception
{
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel buttonPanel = new JPanel();
JPanel containerPanel = new JPanel();
buttonPanel.setLayout(new GridLayout(2,2));
buttonPanel.add(new JButton("1"));
buttonPanel.add(new JButton("2"));
buttonPanel.add(new JButton("3"));
buttonPanel.add(new JButton("4"));
buttonPanel.setPreferredSize(new Dimension(300, 400));
containerPanel.add(buttonPanel);
frame.getContentPane().add(containerPanel);
frame.pack();
frame.setVisible(true);
}
if the dialog gets wider, but stays the same height, the number of rows should lessen, while the number of columns increases.
Wrap Layout might be what you are looking for.
I had a similar issue with a single column of buttons, and found that MiGLayout (third-party, available here) was simple and effective for this. It helped both with making a grid and with setting button sizes, although it took me a day or two to get used to its syntax.
But the key is really setting button sizes; GridLayout certainly seems like the way to go for a layout that is, well, a grid. I haven't tested, but I suspect that the built-in setXSize() methods would work just as well. The GridBagLayout tutorial has examples of some things you can do with sizing/positioning.
FlowLayout would be the way to go but you might have some configuration problems. What layout manager does the parent component use?