Develop Reference

JLabel wont change Width

I'm programming right now a Chomp Game for Uni. Everything works fine but the Label at the bottom. Its background is supposed to fill out the entire bottom. In the attachment you can see how it instead looks now. I tried setting the minimum and the preferred size of the label. The Height is changing but the width just stays adjusted to the text. How can I change that?
Note: The snippet only contains the setting up of the Frame and Panels in a custom method and not the main class.
private void init()
{
JFrame fenster = new JFrame();
this.spielfeld = new SpielfeldPanel(M, N);
this.anzeige = new SpielerAnzeigeLabel(this.spieler);
JPanel panel = new JPanel();
BoxLayout boxlayout = new BoxLayout(panel,BoxLayout.Y_AXIS);
panel.setLayout(boxlayout);
fenster.setTitle("Chomp");
fenster.setSize(1000,700);
panel.setPreferredSize(new Dimension(1000, 60));
Dimension d = new Dimension(getPreferredSize());
panel.setMinimumSize(d);
panel.add(spielfeld);
panel.add(anzeige);
fenster.add(panel);
this.spielfeld.setVisible(true);
this.anzeige.setVisible(true);
panel.setVisible(true);
fenster.setVisible(true);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

A BoxLayout respects the width of the component to the label is displayed at its preferred width/height.
A JFrame uses a BorderLayout by default. So just add the label to the frame independently of the panel:
//panel.add(anzeige);
//fenster.add(panel);
fenster.add(panel, BorderLayout.CENTER);
fenster.add(anzeige, BorderLayout.PAGE_END);
The PAGE_END constraint respects the height but makes the width equal to the space available. Read the section from the Swing tutorial on How to Use BorderLayout for more information and examples.

Use BorderLayout to create two even columns

I'm trying to create a program using BorderLayout() that I want to look like this (but with even left right height and such)
although I am having trouble resizing the two JPanels (two boxes within the large box). At the moment my GUI looks like this,
I believe it is due to the CENTER still being there, I looked up on how to remove it but could not get it to work,
Question
Can can I edit this so that it will look like the top image.
package fuelstation;
import java.awt.*;
import java.util.*;
import javax.swing.*;
public class Fuelstation extends JFrame {
JButton btn1 = new JButton("Random Button");
public Fuelstation() {
JFrame frame = new JFrame("Fuel Station");
frame.setLayout(new BorderLayout());
frame.setResizable(false);
frame.setPreferredSize(new Dimension(500,350));
frame.setMaximumSize(new Dimension(500,350));
// Left Hand Side
JPanel lhs = new JPanel();
JTextArea tf_list = new JTextArea();
tf_list.setEditable(false);
tf_list.setWrapStyleWord(true);
tf_list.setText("This is a list of items");
lhs.add(tf_list);
tf_list.setSize(245, 325);
lhs.setBorder(BorderFactory.createTitledBorder("Left"));
// Left Hand Side End
// Right Hand Side
JPanel rhs = new JPanel();
rhs.setAlignmentX(Component.CENTER_ALIGNMENT);
rhs.setBorder(BorderFactory.createTitledBorder("Right"));
rhs.add(btn1);
tf_list.setSize(245, 325);
JPanel center = new JPanel();
center.setSize(0, 0);
// Right Hand Side End
frame.add(lhs, BorderLayout.WEST);
frame.add(center, BorderLayout.CENTER);
frame.add(rhs, BorderLayout.EAST);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
Fuelstation gui = new Fuelstation();
}
}

You need to drop the requirement to use a BorderLayout. The resizing policy for components when using a BorderLayout is stated in the class javadoc
The components are laid out according to their preferred sizes and the constraints of the container's size. The NORTH and SOUTH components may be stretched horizontally; the EAST and WEST components may be stretched vertically; the CENTER component may stretch both horizontally and vertically to fill any space left over.
By forcing your JFrame to a certain size
frame.setResizable(false);
frame.setPreferredSize(new Dimension(500,350));
frame.setMaximumSize(new Dimension(500,350));
your center component will take the extra width, as the EAST and WEST component will only stretch vertically.
So you need to use another LayoutManager. You can use the Visual guide to layout managers to get a grasp of the available LayoutManagers and their capabilities. That document states that a GridLayout would be a good candidate:
GridLayout simply makes a bunch of components equal in size and displays them in the requested number of rows and columns

Why does my JButton appear the full size of the JFrame?

I am a newbie, I have a question. I am trying to use Eclipse to write a Java windows application, in which I will have a main window, which will contain several things, like a dashboard sort of thing, and it will have buttons, for example to add a record to a database, and this button when pressed, will open a new relevant window on top.
I tried to start, I wrote this code in Java, and for some reason, the button is in the size of the frame...full screen ! How do I fix it ?
Can you suggest me better ideas for a design than what I specified ?
Thank you
public class MainClass {
public static void main(String[] args) {
// TODO Auto-generated method stub
JFrame jfrm = new JFrame("Frame1");
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
jfrm.setSize(screenSize.width, screenSize.height);
jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JLabel jlab = new JLabel("Hello");
jfrm.add(jlab);
JButton button = new JButton("Button");
button.setSize(new Dimension(50, 50));
button.setLocation(500, 350);
jfrm.getContentPane().add(button);
jfrm.setVisible(true);
}

Add a layout to the JFrame first. For example FlowLayout:
jfrm.setLayout(new FlowLayout());

"I tried to start, I wrote this code in Java, and for some reason, the button is in the size of the frame...full screen ! How do I fix it ?"
The reason the button stretches is because JFrame has a default BorderLayout that does not respect the preferred sizes of child components.
The solution is to set the Layout Manager to layout that does respect preferred sizes. The image blow from this example shows the most common Layout Managers and show visually which one respect the preferred size of child components.
Also, the BorderLayout is also the reason your JLabel does not show. By default, every component that is added to a BorderLayout without a position specified e.g. BorderLayout.SOUTH, will automatically be placed in the BorderLayout.CENTER position. Each position may only have one component. So when you add the JLabel it goes to the CENTER, but when you add the JButton, it also goes the CENTER, kicking out the JLabel.
If you've never encountered Layout Managers, this is probably all confusing to you. You should take the time to go over How to Layout Components Within a Container

You need to use some form of layoutmanager, you can use this information: http://docs.oracle.com/javase/tutorial/uiswing/layout/visual.html

You must use Layout manager.
Use this code..
public static void main(String[] args)
{
JFrame jfrm = new JFrame("Frame1");
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
jfrm.setSize(screenSize.width, screenSize.height);
jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JLabel jlab = new JLabel("Hello");
jfrm.add(jlab);
JButton button = new JButton("Button");
button.setSize(new Dimension(50, 50));
button.setLocation(500, 350);
jfrm.add(button);
jfrm.setVisible(true);
jfrm.setLayout(new FlowLayout());
jfrm.pack();
you forgot to add pack(). so use this code to get Jlabel and JButtion side by side.
Thanks...

JScrollPane opening to bottom of panel

I have a JScrollPane on a panel (which has many panels inside of it) and when I open the frame with the scroll pane on it, the fame is scrolled to the bottom. Is there anyway I can avoid this?
Here are some facts:
The panel the scroller is on contains multiple panels. Some of these panels have text fields. I have tried to set the carat of the text fields to 0 and this did not work.
I know there should be actual code, but when I tried to make a mock pane (as the one I am using is intertwined with a lot of code) it is not replicating the issue.
The panel that is being scrolled is being generated using a loop that generates a series of questions... so a text box, a said amount of buttons/answers, and a text box and label that shows the amount of points for each question.
The last elements of my panel that is being scrolled are a JTextArea and a JLabel.
Below is the code to declare those.
Is there anyone out there that could at least throw out an idea of what would be making the scroll pane automatically go to the bottom?
Here is the declaration of the pane and the panels inside/outside of it
JPanel newPanel = new JPanel(new BorderLayout(0, 0));
JPanel showPanel = new JPanel();
BoxLayout layout = new BoxLayout(showQuizPanel, BoxLayout.Y_AXIS);
showQuizPanel.setLayout(layout);
buttonPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
buttonPanel.setBackground(Color.white);
newPanel.setBackground(Color.white);
showPanel.setBackground(Color.white);
populateButtonPanel();
populateShowPanel(showPanel, buttonPanel);
populateQuestions(showPanel);
JScrollPane scrollPane = new JScrollPane(showPanel, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
scrollPane.getViewport().setBackground(Color.WHITE);
scrollPane.setAlignmentX(JScrollPane.CENTER_ALIGNMENT);
scrollPane.getVerticalScrollBar().setUnitIncrement(16);
scrollPane.getVerticalScrollBar().setValue(0);
scrollPane.getViewport().setViewPosition(new Point(0,0));
newPanel.add(scrollPane, BorderLayout.CENTER);
return newPanel;
code to declare last elements on page
JPanel pPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
pPanel.setBackground(Color.WHITE);
pPanel.add(qValue);
pPanel.add(new JLabel("Points"));
qArea.add(pPanel);
qArea.add(Box.createVerticalStrut(50));
qValue.setCaretPosition(0);
Thanks!

I believe that when you add text to a text area when building the GUI, the scroll pane will scroll to make the text area visible.
So basically you need to reset the scroll pane to the top.
You can use code like the following after adding all components to the scroll pane:
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
scrollPane.getViewport().setViewPosition( new Point(0, 0) );
}
});
The invokeLater() adds the code to the end of the Event Dispatch Thread (EDT) so that it gets executed after the GUI is visible.
Of course this code assumes that you are creating the rest of the GUI properly on the EDT.

How to layout multiple panels on a jFrame? (java)

I am in the process of making my own java socket game. My game is painting alright to the full screen (where it says "paint graphics here", but im painting to the whole jframe at the moment). I want to add a textbox with a scroll bar for displaying only text, not taking any input and another textbox to take text inputs from the user and then a button to send the text, for chat purposes. But onto my question, how do I even start to lay this out? I understand I need a layout, but can someone help me on this? Here is my code at the moment (this code only sets up painting to the whole screen at the moment, need to divide the screen up now like I have in the picture above):
public class Setup extends JFrame implements Runnable{
JPanel panel;
JFrame window;
public Setup(Starter start, JFrame window){
window.setSize(600,500);
window.setLocationRelativeTo(null);
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setResizable(false);
panel = new Display(start);
this.window = window;
}
public void run(){
window.getContentPane().add(panel);
window.setBackground(Color.BLACK);
window.setVisible(true);
}
}
"new Display(start)" - this extends jpanel, its basically where I paint everything graphics wise.
In addition, I've seen people add in different panels but I cant have them be the same size. Like in the picture, the "paint graphics here" panel is the biggest one, and so on.

The JPanel is actually only a container where you can put different elements in it (even other JPanels). So in your case I would suggest one big JPanel as some sort of main container for your window. That main panel you assign a Layout that suits your needs ( here is an introduction to the layouts).
After you set the layout to your main panel you can add the paint panel and the other JPanels you want (like those with the text in it..).
JPanel mainPanel = new JPanel();
mainPanel.setLayout(new BoxLayout(mainPanel, BoxLayout.Y_AXIS));
JPanel paintPanel = new JPanel();
JPanel textPanel = new JPanel();
mainPanel.add(paintPanel);
mainPanel.add(textPanel);
This is just an example that sorts all sub panels vertically (Y-Axis). So if you want some other stuff at the bottom of your mainPanel (maybe some icons or buttons) that should be organized with another layout (like a horizontal layout), just create again a new JPanel as a container for all the other stuff and set setLayout(new BoxLayout(mainPanel, BoxLayout.X_AXIS).
As you will find out, the layouts are quite rigid and it may be difficult to find the best layout for your panels. So don't give up, read the introduction (the link above) and look at the pictures – this is how I do it :)
Or you can just use NetBeans to write your program. There you have a pretty easy visual editor (drag and drop) to create all sorts of Windows and Frames. (only understanding the code afterwards is ... tricky sometimes.)
EDIT
Since there are some many people interested in this question, I wanted to provide a complete example of how to layout a JFrame to make it look like OP wants it to.
The class is called MyFrame and extends swings JFrame
public class MyFrame extends javax.swing.JFrame{
// these are the components we need.
private final JSplitPane splitPane; // split the window in top and bottom
private final JPanel topPanel; // container panel for the top
private final JPanel bottomPanel; // container panel for the bottom
private final JScrollPane scrollPane; // makes the text scrollable
private final JTextArea textArea; // the text
private final JPanel inputPanel; // under the text a container for all the input elements
private final JTextField textField; // a textField for the text the user inputs
private final JButton button; // and a "send" button
public MyFrame(){
// first, lets create the containers:
// the splitPane devides the window in two components (here: top and bottom)
// users can then move the devider and decide how much of the top component
// and how much of the bottom component they want to see.
splitPane = new JSplitPane();
topPanel = new JPanel(); // our top component
bottomPanel = new JPanel(); // our bottom component
// in our bottom panel we want the text area and the input components
scrollPane = new JScrollPane(); // this scrollPane is used to make the text area scrollable
textArea = new JTextArea(); // this text area will be put inside the scrollPane
// the input components will be put in a separate panel
inputPanel = new JPanel();
textField = new JTextField(); // first the input field where the user can type his text
button = new JButton("send"); // and a button at the right, to send the text
// now lets define the default size of our window and its layout:
setPreferredSize(new Dimension(400, 400)); // let's open the window with a default size of 400x400 pixels
// the contentPane is the container that holds all our components
getContentPane().setLayout(new GridLayout()); // the default GridLayout is like a grid with 1 column and 1 row,
// we only add one element to the window itself
getContentPane().add(splitPane); // due to the GridLayout, our splitPane will now fill the whole window
// let's configure our splitPane:
splitPane.setOrientation(JSplitPane.VERTICAL_SPLIT); // we want it to split the window verticaly
splitPane.setDividerLocation(200); // the initial position of the divider is 200 (our window is 400 pixels high)
splitPane.setTopComponent(topPanel); // at the top we want our "topPanel"
splitPane.setBottomComponent(bottomPanel); // and at the bottom we want our "bottomPanel"
// our topPanel doesn't need anymore for this example. Whatever you want it to contain, you can add it here
bottomPanel.setLayout(new BoxLayout(bottomPanel, BoxLayout.Y_AXIS)); // BoxLayout.Y_AXIS will arrange the content vertically
bottomPanel.add(scrollPane); // first we add the scrollPane to the bottomPanel, so it is at the top
scrollPane.setViewportView(textArea); // the scrollPane should make the textArea scrollable, so we define the viewport
bottomPanel.add(inputPanel); // then we add the inputPanel to the bottomPanel, so it under the scrollPane / textArea
// let's set the maximum size of the inputPanel, so it doesn't get too big when the user resizes the window
inputPanel.setMaximumSize(new Dimension(Integer.MAX_VALUE, 75)); // we set the max height to 75 and the max width to (almost) unlimited
inputPanel.setLayout(new BoxLayout(inputPanel, BoxLayout.X_AXIS)); // X_Axis will arrange the content horizontally
inputPanel.add(textField); // left will be the textField
inputPanel.add(button); // and right the "send" button
pack(); // calling pack() at the end, will ensure that every layout and size we just defined gets applied before the stuff becomes visible
}
public static void main(String args[]){
EventQueue.invokeLater(new Runnable(){
#Override
public void run(){
new MyFrame().setVisible(true);
}
});
}
}
Please be aware that this is only an example and there are multiple approaches to layout a window. It all depends on your needs and if you want the content to be resizable / responsive. Another really good approach would be the GridBagLayout which can handle quite complex layouting, but which is also quite complex to learn.

You'll want to use a number of layout managers to help you achieve the basic results you want.
Check out A Visual Guide to Layout Managers for a comparision.
You could use a GridBagLayout but that's one of the most complex (and powerful) layout managers available in the JDK.
You could use a series of compound layout managers instead.
I'd place the graphics component and text area on a single JPanel, using a BorderLayout, with the graphics component in the CENTER and the text area in the SOUTH position.
I'd place the text field and button on a separate JPanel using a GridBagLayout (because it's the simplest I can think of to achieve the over result you want)
I'd place these two panels onto a third, master, panel, using a BorderLayout, with the first panel in the CENTER and the second at the SOUTH position.
But that's me