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.
Related
I'm trying to do scrollable list of items that may have buttons inside of them. It's contained within JTabbedPane, and after thorough Googling I'm still not sure how to proceed.
A picture of what I'm trying to achieve:
Best thing that comes to mind is JScrollPane with items as JPanels with BoxLayout and they have "name of item | button | button", although I might be plain wrong and JScrollPane is unable to accept multiple Components.
What I need help with is adding these JPanels to a JScrollPane. How to do that? I tried simple "this.add(name of panel)" and it doesn't work.
// MainWindow:
JTabbedPane tabbedPane = new JTabbedPane();
tabbedPane.addTab("Overview", new OverviewTab());
tabbedPane.addTab("Warehouse", new WarehouseTab());
tabbedPane.addTab("History", new HistoryTab());
public class WarehouseTab extends JScrollPane {
WarehouseTab(){
this.setBorder(null);
this.add(new WarehouseItem());
this.add(new WarehouseItem());
this.add(new WarehouseItem());
this.setVisible(true);
}
public class WarehouseItem extends JPanel {
WarehouseItem(){
this.setLayout(new BoxLayout(this, BoxLayout.X_AXIS));
JButton sell = new JButton("Sell");
JButton tax = new JButton("Return tax");
JLabel name = new JLabel("Item name");
this.add(name);
this.add(tax);
this.add(sell);
}
I also tried packing my JPanels into Container and then pointing JScrollPane's viewport to it, as suggested on some other forums, but it didn't work either. What else should it try?
Any suggestions would be appreciated, thanks.
although I might be plain wrong and JScrollPane is unable to accept multiple Components.
Yes, you're right, JScrollPane manages a single "view". What you should so is start with a separate JPanel which acts as the "primary" container for your other elements and then wrap that in a JScrollPane
public class WarehouseTab extends JPanel {
public WarehouseTab() {
setLayout(new BorderLayout());
add(new JScrollPane(new WarehousePane());
}
}
public class WarehousePane extends JPanel {
WarehousePane(){
setLayout(...); // Set an appropriate layout for overall needs
this.add(new WarehouseItem());
this.add(new WarehouseItem());
this.add(new WarehouseItem());
}
Also, have a look at How to Use Scroll Panes and the JavaDocs which provide more information about how JScrollPane works
I read some answered questions in this forum (this one for example) where it is strictly recommended to avoid the use of setXXXSize() methods to resize components in swing applications.
So, coming to my problem, i would like to know how to best resize a JScrollPane in order to avoid its parent panel to increase its size without any control.
Before writing some code, i want to describe the real situation, since i will post a "toy example".
In my JFrame i'm currently using a border layout for my content pane. At BorderLayout.CENTER there is a JPanel where i do some custom painting.
At BorderLayout.EAST there is a JPanel (say eastPanel) containing some components inside another panel (this panel will be added to eastPanel at BorderLayout.NORTH), and a JScrollPane which contains a JTable (added to eastPanel at BorderLayout.CENTER). This table will have a lot of rows.
Since i want eastPanel's height to be the same as centerPanel's height, i need some way to avoid the JScrollPane to increase its size in order to try to display as much rows as possible.
For now i wasn't be able to find another solution apart from calling setPreferredSize on the eastPanel containing the scrollpane, but i have to admit that i hate this kind of solution.
Sample Code
In this code sample i added some random labels at the north of eastPanel and inside the JScrollPane, since my purpose was to post a short sample of code.
However, the situation is very similar to the one i have described above.
I wasn't be able to solve my problem without using this "terrible" line of code :
eastPanel.setPreferredSize(new Dimension(eastPanel.getPreferredSize().width, centerPanel.getPreferredSize().height));
I would like to avoid a more complex layout for a simple situation like this. Am i missing something ? Also, is setting that empty border an acceptable way to set the size of the panel where i will do some custom painting?
Code :
import java.awt.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
public class Test
{
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
new TestFrame().setVisible(true);
}
catch(Exception exception) {
JOptionPane.showMessageDialog(null, "Fatal error while initialiing application", "Error", JOptionPane.ERROR_MESSAGE);
}
}
});
}
}
class TestFrame extends JFrame
{
public TestFrame() {
super("Test");
setDefaultCloseOperation(EXIT_ON_CLOSE);
JPanel pane = new JPanel(new BorderLayout(20, 0));
pane.setBorder(new EmptyBorder(20, 20, 20, 20));
JPanel centerPanel = new JPanel();
centerPanel.setBackground(Color.WHITE);
centerPanel.setBorder(new EmptyBorder(400, 400, 0, 0));
// centerPanel.setPreferredSize(new Dimension(400, 400));
JPanel eastPanel = new JPanel(new BorderLayout(0, 20));
JPanel labelsContainer = new JPanel(new GridLayout(0, 1));
for(int i=0;i<7;i++) labelsContainer.add(new JLabel(String.valueOf(i)));
eastPanel.add(labelsContainer, BorderLayout.NORTH);
JPanel moreLabelsContainer = new JPanel(new GridLayout(0, 1));
for(int i=7;i<70;i++) moreLabelsContainer.add(new JLabel(String.valueOf(i)));
JScrollPane scroll = new JScrollPane(moreLabelsContainer, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
eastPanel.add(scroll, BorderLayout.CENTER);
eastPanel.setPreferredSize(new Dimension(eastPanel.getPreferredSize().width, centerPanel.getPreferredSize().height));
pane.add(centerPanel, BorderLayout.CENTER);
pane.add(eastPanel, BorderLayout.EAST);
setContentPane(pane);
pack();
setLocationRelativeTo(null);
}
}
Thanks for your help !
I am not aware of a layout manager that restricts the height of the panel based on the height of a specific component in the panel.
One way is to customize the behaviour of the parent panel that contains the two child components.
The code might be something like:
#Override
public Dimension getPreferredSize()
{
Dimension d = super.getPreferredSize();
BorderLayout layout = (BorderLayout)getLayout();
Component center = layout.getLayoutComponent(BorderLayout.CENTER);
int centerHeight = center.getPreferreidSize().height;
if (d.height > centerHeight)
d.height = centerHeight;
return d;
}
This approach will allow for dynamic calculation of the height based on the component in the center.
Another option is to write you own layout manager. Then you can control this type of logic from within the layout manager.
Also, is setting that empty border an acceptable way to set the size of the panel where i will do some custom painting?
I override the getPreferredSize() to return the appropriate dimension.
By using the EmptyBorder you lose the ability to add a true Border to the panel, so I wouldn't recommend it.
So I'm writing a program in which I wish to have a single JFrame containing a JPanel header in a separate colour and directly underneath have a grid of buttons in a separate JPanel. So far my program works perfectly except for the fact that the header String isn't showing up in the NORTH panel. Instead I'm getting a box containing the set background colour with a small grey box in the centre. I'm wondering if I didn't set the size of the panel correctly?
I have heard this can be accomplished using JLabel, but when I tried to do this, it would not show the background colour that I had set.
So, could anyone please show me how to achieve the following either with the JPanel (preferably because I would like to know how it works and what I'm missing) or with JLabel: filling that little grey box in the middle of the header with a String.
Here is my code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Example {
public static void main(String[] args) {
// Initialize a panel for the header, and mainGrid which will contain buttons
JPanel panel = new JPanel();
JPanel header = new JPanel();
JPanel mainGrid = new JPanel();
// Initialize the header
DisplayPanel message = new DisplayPanel();
header.setBackground(Color.ORANGE);
header.add(message);
// Initialize the mainGrid panel
mainGrid.setLayout(new GridLayout(2,2,2,2));
mainGrid.add(new JButton("1"));
mainGrid.add(new JButton("2"));
mainGrid.add(new JButton("3"));
mainGrid.add(new JButton("4"));
// Add the two subpanels to the main panel
panel.setLayout(new BorderLayout());
panel.add(header, BorderLayout.NORTH); // The issue is this panel isn't displaying the String created in DisplayPanel
panel.add(mainGrid, BorderLayout.CENTER);
// Add main panel to JFrame
JFrame display = new JFrame("Test");
display.setContentPane(panel);
display.setSize(200,100);
display.setLocation(500,200);
display.setVisible(true);
display.setResizable(false);
display.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
private static class DisplayPanel extends JPanel {
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawString("header" , 20, 20); // The string I want to be displayed
}
}
}
I would very much appreciate anyone's help or input as I have only been studying Java for a few months and this is my first post. Thank you in advance.
Also, any general tips on writing that you may have would be greatly appreciated.
I'm wondering if your problem is that you're nesting your message JPanel inside of the header JPanel, and the container header JPanel uses the JPanel default FlowLayout. Thus the component it holds won't expand on its own and will remain trivially small.
Consider either giving the header JPanel a BorderLayout so that message expands inside of it, or
use a JLabel to show your text, not a JPanel's paintComponent method. The JLabel should size itself to be big enough to show its text. If you do this and want it to show a background color, all you have to do is call setOpaque(true) on your JLabel, and you're set.
Actually, if you nest the JLabel, then there's no need to make it opaque. Just do this:
JPanel header = new JPanel();
JPanel mainGrid = new JPanel();
JLabel message = new JLabel("Header", SwingConstants.CENTER);
header.setBackground(Color.ORANGE);
header.setLayout(new BorderLayout());
header.add(message);
I would highly recommend using a GUI builder WYSIWYG IDE, like NetBeans, where you can easily drag and drop components to where they need to be. If you're doing any sort of complex GUI layout, it can be madness (and in my opinion, nonsensical) trying to write and maintain the code.
The layout your trying to implement would be trivial in NetBeans.
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();
I'm playing around with some swing guis and am trying to create a basic program. This program is going to have a tabbed pane with a varying amount of tabs depending on the size of an array. (My end goal is to have users change the amount of items in the array, therefore changing the amount of tabs).
Each tab is going to have the exact same components, text area, table and a few buttons and labels. What I would like to do is instead of coding these tabs individually and rewriting my code over and over what I want to do is create a class to put all my components into.
I am however kind of stumped. This is my class for creating the tabs:
public class LocaleTab {
public LocaleTab(){
JPanel tab = new JPanel();
JLabel label = new JLabel();
label.setPreferredSize(new Dimension(300, 300));
tab.add(label);
}
}
And here's my code that I'm trying to call with it:
LocaleTab tab1 = new LocaleTab();
JTabbedPane localesTabPane = new JTabbedPane();
localesTabPane.add(tab1);
I'm getting an error when I try and compile this. I'm thinking my methodology is probably completely wrong.
The method add(Component) in the type JTabbedPane is not applicable
for the arguments (LocaleTab)
One are that concerns me is when I try to use the data in the tables and text areas in each tab(event listeners is what I'll be using i think? I haven't gotten to that stage yet though!) how will I target the individual tabs components?
Change to:
public class LocaleTab extends JPanel {
public LocaleTab(){
JLabel label = new JLabel();
label.setPreferredSize(new Dimension(300, 300));
add(label);
}
}
Probably you are looking for something close to this:
public class LocaleTab {
private JPanel tab;
public LocaleTab() {
tab = new JPanel();
JLabel label = new JLabel();
label.setPreferredSize(new Dimension(300, 300));
tab.add(label);
}
public JPanel getTabPanel() {
return tab;
}
}
And use LocaleTab as shown below.
LocaleTab tab1 = new LocaleTab();
JTabbedPane localesTabPane = new JTabbedPane();
localesTabPane.add(tab1.getTabPanel());
Additionally to know about how JTabbedPane works please take a look here: How to Use Tabbed Panes