I'm simply trying to add a JLabel to an existing JPanel. This seems really simple, and I've searched all around. I think that this is right, but the label is not appearing on my panel. Anybody see what I am missing? Thanks!
ResultsPanel myPanel = new ResultsPanel(pnlResults); //pnlResults is an existing JPanel
myPanel.addLabel(pnlResults);
public class ResultsPanel extends JPanel {
JPanel myPanel;
public ResultsPanel(JPanel thisPanel) {
myPanel = thisPanel;
}
public void addLabel(JPanel myResults) {
JLabel myLabel = new JLabel("test", JLabel.LEFT);
myPanel.setLayout(new FlowLayout());
add(myLabel);
}
}
EDIT: In response to the immediate replies below, I agree that this seems to be total overkill. I went down this path because the following code also does not result in a JLabel being added to my JPanel:
JLabel myLabel = new JLabel("test");
pnlResults.add(myLabel);
I would much rather use this code, so feel free to comment on this if you think it is more likely to work (with some modifications, of course). Thanks again!
This seems to be jumping through hoops just to do a basic thing; simply call
JLabel label = new JLabel("Test text");//initialize the label
//do some stuff with label here maybe...
panel.add(label);//now add it
There is no need to make a class extends JPanel, and contain a JPanel; if a class extends JPanel, to get the JPanel instance, simply use this (so addLabel would instead do this.setLayout(blah)). But of course there is no need to even subclass JPanel for something as simple as adding a JLabel
Overall, here's pretty much the simplest swing application:
JFrame frame = new JFrame("Basic Swing");//Make a frame
frame.setSize(300, 300);//Give it a size
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);//Make it go away on close
JPanel panel = new JPanel();//Make a panel
frame.add(panel);//Add it to your frame
JLabel label = new JLabel("Hello StackOverflow!");//Make a label
panel.add(label);//Add it to the panel (which is on the frame)
frame.setVisible(true);//Show the frame
Firstly, you've extended from JPanel
Secondly, you've supplied you're own JPanel
Now, from your code snippet, there's no way to determine if either ResultsPane or myPanel have been added to a Container of any kind, but from what you're saying, I'd suggest that would be your primary problem.
Do you really want/need to have an actual JLabel object? If not, you can label your panel as follow:
public void addLabel() {
myPanel.setBorder(new TitledBorder("test"));
}
Try this
JLabel myLabel = new JLabel("test text");
myLabel.setSize(myLabel.getPreferredSize());
panel.add(myLabel);
panel.revalidate();
panel.repaint();
Related
I'm using the NetBeans GUI builder to handle my layout (I'm terrible with LayoutManagers) and am trying to place a simple JLabel so that it is always centered (horizontally) inside its parent JPanel. Ideally, this would maintain true even if the JPanel was resized, but if that's a crazy amount of coding than it is sufficient to just be centered when the JPanel is first created.
I'm bad enough trying to handle layouts myself, but since the NetBeans GUI Builder autogenerates immutable code, it's been impossible for me to figure out how to do this centering, and I haven't been able to find anything online to help me.
Thanks to anybody who can steer me in the right direction!
Here are four ways to center a component:
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
class CenterComponent {
public static JLabel getLabel(String text) {
return getLabel(text, SwingConstants.LEFT);
}
public static JLabel getLabel(String text, int alignment) {
JLabel l = new JLabel(text, alignment);
l.setBorder(new LineBorder(Color.RED, 2));
return l;
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JPanel p = new JPanel(new GridLayout(2,2,4,4));
p.setBackground(Color.black);
p.setBorder(new EmptyBorder(4,4,4,4));
JPanel border = new JPanel(new BorderLayout());
border.add(getLabel(
"Border", SwingConstants.CENTER), BorderLayout.CENTER);
p.add(border);
JPanel gridbag = new JPanel(new GridBagLayout());
gridbag.add(getLabel("GridBag"));
p.add(gridbag);
JPanel grid = new JPanel(new GridLayout());
grid.add(getLabel("Grid", SwingConstants.CENTER));
p.add(grid);
// from #0verbose
JPanel box = new JPanel();
box.setLayout(new BoxLayout(box, BoxLayout.X_AXIS ));
box.add(Box.createHorizontalGlue());
box.add(getLabel("Box"));
box.add(Box.createHorizontalGlue());
p.add(box);
JFrame f = new JFrame("Streeeetch me..");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setContentPane(p);
f.pack();
f.setLocationByPlatform(true);
f.setVisible(true);
}
});
}
}
By using Borderlayout, you can put any of JComponents to the CENTER area. For an example, see an answer to Stack Overflow question Get rid of the gap between JPanels. This should work.
Even with BoxLayout you can achieve that:
JPanel listPane = new JPanel();
listPane.setLayout(new BoxLayout(listPane, BoxLayout.X_AXIS ));
JLabel label = new JLabel();
listPane.add(Box.createHorizontalGlue());
listPane.add(label);
listPane.add(Box.createHorizontalGlue());
mKorbel's solution is perfect for your goal. Anyway I always like to suggest BoxLayout because it's very flexible.
Mara: "thanks for your response, however the NetBeans GUI Build uses GroupLayout and this is not overridable."
Not true! Right click anywhere inside JFrame (or any other GUI container) in NetBeans GUI builder and select "Set Layout". By default is selected "Free Design", which is Group layout, but you can select any other layout including Border layout as advised by mKorbel.
There's many ways to do this, depending on the layout manager(s) you use. I suggest you read the Laying Out Components Within a Container tutorial.
I believe the following will work, regardless of layout manager:
JLabel.setHorizontalAlignment(SwingConstants.CENTER)
I've tried a lot of different ways, but I will explain two and what was happening (no error messages or anything, just not showing up like they should or just not showing up at all):
First, I created a JPanel called layout and set it as a BorderLayout. Here is a snippet of how I made it look:
JPanel layout = new JPanel();
layout.setLayout(new BorderLayout());
colorChoice = new JLabel("Choose your color: ");
layout.add(colorChoice, BorderLayout.NORTH);
colorBox = new JComboBox(fireworkColors);
colorBox.addActionListener(this);
layout.add(colorBox, BorderLayout.NORTH);
In this scenario what happens is they don't show up at all. It just continues on with whatever else I added.
So then I just tried setLayout(new BorderLayout()); Here is a snippet of that code:
setLayout(new BorderLayout());
colorChoice = new JLabel("Choose your color: ");
add(colorChoice, BorderLayout.NORTH);
colorBox = new JComboBox(fireworkColors);
colorBox.addActionListener(this);
add(colorBox, BorderLayout.NORTH);
In this scenario they are added, however, the width takes up the entire width of the frame and the textfield (not shown in the snippet) takes up basically everything else.
Here is what I have tried:
setPreferredSize() & setSize()
Is there something else that I am missing? Thank you.
I also should note that this is a separate class and there is no main in this class. I only say this because I've extended JPanel instead of JFrame. I've seen some people extend JFrame and use JFrame, but I haven't tried it yet.
You created a JPanel, but didn't add it to any container. It won't be visible until it is added to something (a JFrame, or another panel that is in a frame somewhere up the hierarhcy)
You added two components to the same position in the BorderLayout. The last one added is the one that will occupy that position.
Update:
You do not need to extend JFrame. I never do, instead I always extend JPanel. This makes my custom components more flexible: they can be added in another panel, or they can be added to a frame.
So, to demonstrate the problem I will make an entire, small, program:
public class BadGui
{
public static void main(String[] argv)
{
final JFrame frame = new JFrame("Hello World");
final JPanel panel = new JPanel();
panel.add(new JLabel("Hello"), BorderLayout.NORTH);
panel.add(new JLabel("World"), BorderLayout.SOUTH);
frame.setVisible(true);
}
}
In this program I created a panel, but did not add it to anything so it never becomes visible.
In the next program I will fix it by adding the panel to the frame.
public class FixedGui
{
public static void main(String[] argv)
{
final JFrame frame = new JFrame("Hello World");
final JPanel panel = new JPanel();
panel.add(new JLabel("Hello"), BorderLayout.NORTH);
panel.add(new JLabel("World"), BorderLayout.SOUTH);
frame.getContentPane().add(panel);
frame.setVisible(true);
}
}
Note that in both of these, when I added something to the panel, I chose different layout parameters (one label I put in 'North' and the other in 'South').
Here is an example of a JPanel with a BorderLayout that adds a JPanel with a button and label to the "North"
public class Frames extends JFrame
{
public Frames()
{
JPanel homePanel = new JPanel(new BorderLayout());
JPanel northContainerPanel = new JPanel(new FlowLayout());
JButton yourBtn = new JButton("I Do Nothing");
JLabel yourLabel = new JLabel("I Say Stuff");
homePanel.add(northContainerPanel, BorderLayout.NORTH);
northContainerPanel.add(yourBtn);
northContainerPanel.add(yourLabel);
add(homePanel);
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
setLocationRelativeTo(null);
setExtendedState(JFrame.MAXIMIZED_BOTH);
setTitle("Cool Stuff");
pack();
setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(Frames::new);
}
}
The below suggestion is assuming that your extending JFrame.
Testing
First of all, without seeing everything, theres always a numerous amount of things you can try.
First off, after you load everything, try adding this in (Again, assuming your extending JFrame:
revalidate();
repaint();
I add this into my own Swing projects all the time, as it refreshes and checks to see that everything is on the frame.
If that doesn't work, make sure that all your JComponent's are added to your JPanel, and ONLY your JPanel is on your JFrame. Your JFrame cannot sort everything out; the JPanel does that.
JPanel window = new JPanel();
JButton button = new JButton("Press me");
add(window);
window.add(button); // Notice how it's the JPanel that holds my components.
One thing though, you still add your JMenu's and what-not through your JFrame, not your JPanel.
I have an applet and I want to add a jbutton. The problem is the button is too big, I already used the setSize() method but still it doesn't work. Perhaps the setting of setSize could might be wrong.
could someone got an idea about this problem?
Thanks...
private JButton newGame = new JButton("New Game");
private JButton players = new JButton("Players");
private JButton quit = new JButton("Quit");
public void init()
{
Container content = getContentPane();
content.setLayout(new BorderLayout());
mainPanel = new JPanel();
getContentPane().add(mainPanel);
setVisible(true);
setSize(400, 400);
content.add(newGame);
content.add(players);
content.add(quit);
}
Please check the layout manager you are using for your container (panel, frame, applet..). This plays a major role in defining the size & position of components (like JButton).
See also in the Java Tutorial for more details:
Using Layout Managers.
The Laying Out Components Within a Container lesson.
Add JPanel into your applet and then add JButton to it
The tree code conception is
JApplet (GridLayout) <- JPanel (FlowLayout) <- JButton (setSize(new Dimension(x,y)))
Good Luck
I'm using the NetBeans GUI builder to handle my layout (I'm terrible with LayoutManagers) and am trying to place a simple JLabel so that it is always centered (horizontally) inside its parent JPanel. Ideally, this would maintain true even if the JPanel was resized, but if that's a crazy amount of coding than it is sufficient to just be centered when the JPanel is first created.
I'm bad enough trying to handle layouts myself, but since the NetBeans GUI Builder autogenerates immutable code, it's been impossible for me to figure out how to do this centering, and I haven't been able to find anything online to help me.
Thanks to anybody who can steer me in the right direction!
Here are four ways to center a component:
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
class CenterComponent {
public static JLabel getLabel(String text) {
return getLabel(text, SwingConstants.LEFT);
}
public static JLabel getLabel(String text, int alignment) {
JLabel l = new JLabel(text, alignment);
l.setBorder(new LineBorder(Color.RED, 2));
return l;
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JPanel p = new JPanel(new GridLayout(2,2,4,4));
p.setBackground(Color.black);
p.setBorder(new EmptyBorder(4,4,4,4));
JPanel border = new JPanel(new BorderLayout());
border.add(getLabel(
"Border", SwingConstants.CENTER), BorderLayout.CENTER);
p.add(border);
JPanel gridbag = new JPanel(new GridBagLayout());
gridbag.add(getLabel("GridBag"));
p.add(gridbag);
JPanel grid = new JPanel(new GridLayout());
grid.add(getLabel("Grid", SwingConstants.CENTER));
p.add(grid);
// from #0verbose
JPanel box = new JPanel();
box.setLayout(new BoxLayout(box, BoxLayout.X_AXIS ));
box.add(Box.createHorizontalGlue());
box.add(getLabel("Box"));
box.add(Box.createHorizontalGlue());
p.add(box);
JFrame f = new JFrame("Streeeetch me..");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setContentPane(p);
f.pack();
f.setLocationByPlatform(true);
f.setVisible(true);
}
});
}
}
By using Borderlayout, you can put any of JComponents to the CENTER area. For an example, see an answer to Stack Overflow question Get rid of the gap between JPanels. This should work.
Even with BoxLayout you can achieve that:
JPanel listPane = new JPanel();
listPane.setLayout(new BoxLayout(listPane, BoxLayout.X_AXIS ));
JLabel label = new JLabel();
listPane.add(Box.createHorizontalGlue());
listPane.add(label);
listPane.add(Box.createHorizontalGlue());
mKorbel's solution is perfect for your goal. Anyway I always like to suggest BoxLayout because it's very flexible.
Mara: "thanks for your response, however the NetBeans GUI Build uses GroupLayout and this is not overridable."
Not true! Right click anywhere inside JFrame (or any other GUI container) in NetBeans GUI builder and select "Set Layout". By default is selected "Free Design", which is Group layout, but you can select any other layout including Border layout as advised by mKorbel.
There's many ways to do this, depending on the layout manager(s) you use. I suggest you read the Laying Out Components Within a Container tutorial.
I believe the following will work, regardless of layout manager:
JLabel.setHorizontalAlignment(SwingConstants.CENTER)
I have a GUI im building to illustrate a tree. The JPanel that I extended isnt showing the JLabel that I created when I constructed the JPanel. Here is my JPanel code:
class NodePanel extends JPanel {
private JLabel content;
NodePanel() {
this.setLayout(new FlowLayout());
this.setBorder(new LineBorder(Color.black));
}
NodePanel(String str) {
this.setLayout(new FlowLayout());
this.setBorder(new LineBorder(Color.black));
content = new JLabel(str);
this.add(content);
}
}
and here is the code where im testing it:
NodePanel n1 = new NodePanel(Integer.toString(root.getWeight()));
HuffmanGUI.tp.add(n1);
n1.setBounds((tpWidth / 2) - (panelDim / 2), vertSpace, panelDim, panelDim);
This code is in a method called by an action listener, I know it works because the panel shows up where its supposed to, but the Jlabel isnt displayed inside it. Why could this be?
Its hard to tell because we don't know the context of how the code is used. It looks like you are mixing null layouts with layout managers.
I might guess that you are adding the panel to a visible GUI and you haven't used revalidate() on the panel so the label doesn't have a size.
If you need more help then post your SSCCE that demonstrates the problem.