I'm working on a class extending JDialog. I have a JPanel field named "panel" inside it, which is added to the contentPane (another JPanel), and I add the components that are intended to be displayed to "panel".
"Panel" always has the same size as the window itself. (It's practically a duplicate of contentPane.) But the window's size is different by every run, its size is counted in the constructor of the class based on the value of some specific fields that come from the program's business logic. (This size is static through one run, but when writing the code I don't know the exact numbers yet, only the method how to count it.)
This size could sometimes be very big, but I never want my window to be bigger than a specific size, e.g. (1300,800). When the window would be not larger than this size, I don't want the scrollbars to appear. When it would be larger than this on one dimension only, I only want the appropriate scrollbar to appear (vertical / horizontal). And when it's larger on both dimensions, then both scrollbars should appear.
I have read at least 50 tutorials and questions on this topic, here and on other similar forums. And I tried every idea that I found, in every different combination I could only think of. But none of them worked, and now I'm already very desperate.
It might be because neither my contentPane, nor "panel" uses a layout manager. They both use null. I read by another question that we have to set the preferred size of the component we want to be scrolled, but setPreferredSize leans on a layout manager. They there wrote that they don't really have an idea how to solve this issue, else than starting using a layout manager.
But if I start using one, it confuses the layout that I have designed, it ruins the x, y values, which I have set manually by each component. Layout is important in my exercise. It's not right if a layout manager confuses it, and I don't really like for this excercise how the different layout managers set the layout.
Could you give me any ideas on how I could make scrollbars work keeping using null layout manager?... :/
Here's my class Kimenet (Kimenet is the word for "output" in my mother tongue):
public class Kimenet extends JDialog {
private JPanel contentPane, panel;
private int window_width, window_height;
public static Kimenet showDialog(...) {...}
public Kimenet(...){
window_width = ...; //some counting here
window_height = ...; //some counting here
GUI();
}
private void GUI(){
setBounds(0, 0, window_width, window_height);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
contentPane.setLayout(null);
setContentPane(contentPane);
panel = new JPanel();
panel.setLayout(null);
panel.setBounds(0, 0, window_width, window_height);
contentPane.add(panel);
//here is where I try to add the scrollbars in every desperate way......
... components that I wanna add: panel.add(component);
}
Here's the part of the Main class from where I make an instance of Kimenet:
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Kimenet dialog = Kimenet.showDialog();
dialog.setDefaultCloseOperation(JDialog.HIDE_ON_CLOSE);
dialog.setModal(true);
dialog.setVisible(true);
System.exit(0);
} catch (Exception e) {
e.printStackTrace();
}
}
});
I have tried adding the scrollbars from Main before making the dialog visible, and from Kimenet's GUI() method as well.
I have tried creating JScrollPane in many different combinations, but this mostly resulted that the scrollbars still didn't appear, but every component that I added to "panel" disappeared.
panel.setPreferredSize(new Dimension(1000, 600));
JScrollPane scrollpane = new JScrollPane(panel);
panel.setAutoscrolls(true);
scrollpane.setPreferredSize(new Dimension(800, 300));
this.add(scrollpane);
I've tried here this.add(scrollpane), contentPane.add(scrollpane), panel.add(scrollpane), scrollpane.add(contentPane) and many combinations.
I have tried creating JScrollBars separately in many different combinations too, but this mostly resulted that the scrollbars simply didn't appear (I have tried much more combinations than what I copy here, e.g. vertical and horizontal scrollbar policy.)
vertikális = new JScrollBar(JScrollBar.VERTICAL, 0, 10, 0, 100);
vertikális.setPreferredSize(new Dimension(700, 600));
contentPane.add(vertikális);
This didn't work in no way either.
Related
I have been searching for a while now, but couldnt find a solution so I have decided to ask here.
I am using Java Swing for my gui implementation of calculator. I have custom made layout(which works correctly 100%). I have added all buttons and all buttons are positioned correctly, always. Last component I have inserted is "Inv" and it is checkbox which I cant find a way to center it inside its area. I have tried putting it in panel,in panel with borderlayout.center, setting the horizontal and vertical text alignment, but nothing works.
invert = new JCheckBox("Inv");
invert.setBackground(Color.decode("#8DA336"));
invert.addActionListener(new CommandListener(this,"invert"));
container.add(invert, new RCPosition(5, 7));
This RCPosition is nothing more than object which says in which row and column this component is (nothing wrong with that).
Checkbox is by default left-aligned. Try make it center-aligned:
invert = new JCheckBox("Inv");
invert.setHorizontalAlignment(SwingConstants.CENTER);
// styling and add to container
If it don't help, then you should publish your layout manager.
You could try putting it in a JPanel with BoxLayout, then add horizontal glue on the left and right.
final JFrame frame = new JFrame();
final JPanel jp = new JPanel();
jp.setLayout(new BoxLayout(jp, BoxLayout.X_AXIS));
jp.add(Box.createHorizontalGlue());
final JCheckBox jcb = new JCheckBox("inv");
jp.add(jcb);
jp.add(Box.createHorizontalGlue());
frame.getContentPane().add(jp);
frame.pack();
frame.setLocationRelativeTo(null);
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
frame.setVisible(true);
}
});
This is just one way to do it, setHorizontalAlignment should work as well.
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.
We're about to create an online based Space Invaders-game with implemented graphics. I've been reading about JFrames, JPanels and JLabels in order to create a window with a grid where the ships and monsters will be placed in.
So, here's the thing, I've been looking through the different layouts that exists, but nothing really seems to fit our purpose. I would like a simple JFrame with the possibility of placing JLabel-objects on a certain position (with setBounds(), setLocation() or something similar). This requires setLayout(null) which I've heard isn't a good solution? I was thinking of having objects in a fixed 30x30px size, and a fixed window size of 600x600px (giving me a grid of 20*20).
Anyhow, I've been trying to get it to work with setLayout(null), but without any results. If I apply a layout, say FlowLayout, the ship is visible, but stuck in either LEFT, CENTER or MIDDLE.
public class GUI extends JFrame {
JPanel p = new JPanel(null);
public GUI() {
try{
this.setContentPane(new JLabel(new ImageIcon(ImageIO.read(new File("graphics/bg.png")))));
}catch(IOException e) {
System.out.println("Image does not exist");
}
this.setLayout(null);
this.setResizable(false);
this.setSize(600,600);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLocationRelativeTo(null);
this.setVisible(true);
}
public void placeShip1() {
ImageIcon ship2 = new ImageIcon("graphics/ship2.png");
JLabel imageLabel = new JLabel(ship2);
imageLabel.setBounds(200,200,30,30);
p.add(imageLabel);
p.setOpaque(false);
p.setSize(600, 600);
this.add(p);
this.setVisible(true);
}
}
I really can't see why it doesn't work. I mean, all I want is my JFrame with a background image and with an object on a certain position, but instead the object doesn't show at all.
The main reason for wanting to use setLayout(null) is because I was thinking of using a method translating our grid coordinates to the JFrame, simply mapping each coordinate to respective cell.
I am trying to learn GUI from a book I just got, but I am having tons of problems (my code is attached). When I launch this app, All I get is a minimum window that need to expand every time, and the only thing it shows is one of my radio buttons. I am obviously doing something wrong here. Can somebody please advise me?
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class CarPayment
{
public static void main(String[] args)
{
new CarPaymentCalc();
} // main
} // CarPayment
class CarPaymentCalc extends JFrame
{
private JLabel labelTitle, labelInterest, labelLoan;
private JTextField tfLoan, tfInterest, tfAnswer;
private ButtonGroup bgSelect;
private JRadioButton rbPmts36, rbPmts48, rbPmts60;
private JButton bClear;
public CarPaymentCalc()
{
setVisible(true);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLocationRelativeTo(null); // Centers the window
setTitle("Car Payments Calculator");
// Labels
labelTitle = new JLabel("Calculate My Car Payment");
labelTitle.setVerticalAlignment(JLabel.TOP);
add(labelTitle, JLabel.CENTER);
labelLoan = new JLabel("Loan Amount");
labelLoan.setLocation(0, 10);
add(labelLoan);
labelInterest = new JLabel("Interest");
labelInterest.setLocation(0, 45);
add(labelInterest);
// Input Fields
tfLoan = new JTextField(20);
tfLoan.setLocation(0, 25);
add(tfLoan);
tfInterest = new JTextField(5);
tfInterest.setLocation(0, 60);
add(tfInterest);
JTextArea tfAnswer = new JTextArea(50,10);
tfAnswer.setLocation(0, 110);
add(tfAnswer);
// Radio buttons
bgSelect = new ButtonGroup();
rbPmts36 = new JRadioButton();
rbPmts36.setText("36 Payments");
rbPmts36.setLocation(0, 80);
bgSelect.add(rbPmts36);
add(rbPmts36);
bgSelect.add(rbPmts48);
rbPmts48.setText("48 Payments");
rbPmts48.setLocation(150, 80);
rbPmts48 = new JRadioButton();
add(rbPmts48);
bgSelect.add(rbPmts60);
rbPmts60.setText("60 Payments");
rbPmts60.setLocation(300, 80);
rbPmts60 = new JRadioButton();
add(rbPmts60);
setLayout(null);
pack();
} // CarPaymentCalc
}
Don't use null layouts. Pixel perfect layouts are an illusion in modern UI design, you have no control over fonts, DPI, rendering pipelines or other factors that will change the way that you components will be rendered on the screen.
Swing was designed to work with layout managers to overcome these issues. If you insist on ignoring these features and work against the API design, be prepared for a lot of headaches and never ending hard work.
By looking at JavaDocs for pack...
Causes this Window to be sized to fit the preferred size and layouts
of its subcomponents. The resulting width and height of the window are
automatically enlarged if either of dimensions is less than the
minimum size as specified by the previous call to the setMinimumSize
method. If the window and/or its owner are not displayable
yet, both of them are made displayable before calculating the
preferred size. The Window is validated after its size is being
calculated.
You will note that pack relies on the layout manager API to determine the preferred viewable size of the frames content. By setting the layout manager to null, you've prevented it from been able to determine this information, so basically, it's done nothing.
If your book is telling you to use null layouts, get rid of it, it's not teaching you good habits or practices.
Take a look at Laying Out Components Within a Container for more details about layout managers and how to use them
Other problems you are having:
Calling setVisible(true); before you've finished building the UI can sometimes prevent the UI from appearing the way you intended it to. You could call revalidate on the frame, but it's simpler to just call setVisible last.
The calculation used by setLocationRelativeTo uses the frames current size, but this hasn't been set yet. Instead, you should do something like:
public CarPaymentCalc() {
//...build UI here with appropriate layout managers...
pack();
setLocationRelativeTo(null);
setVisible(true);
}
I would also discourage you from extending directly from top level containers like JFrame, apart from the fact that you're not adding any functionality to the frame per se, it prevents you from re-using the IU later.
Better to start with a JPanel and add this to whatever you want, but that's just me.
After manually swapping components via add and remove, I invoke validate() on the container. According to the documentation,
The validate method is used to cause a container to lay out its
subcomponents again. It should be invoked when this container's
subcomponents are modified (added to or removed from the container, or
layout-related information changed) after the container has been
displayed.
The phrase "lay out its subcomponents again" makes me think that the container will resize itself accordingly, but it doesn't. Instead, after invoking validate(), I need to invoke pack() as well in order to view all its subcomponents.
Why is this? Am I doing something wrong?
I think that you answered your question by yourself, hope help you this demo
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.LineBorder;
public class AddComponentsAtRuntime {
private JFrame f;
private JPanel panel;
private JCheckBox checkValidate, checkReValidate, checkRepaint, checkPack;
public AddComponentsAtRuntime() {
JButton b = new JButton();
b.setBackground(Color.red);
b.setBorder(new LineBorder(Color.black, 2));
b.setPreferredSize(new Dimension(600, 10));
panel = new JPanel(new GridLayout(0, 1));
panel.add(b);
f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(panel, "Center");
f.add(getCheckBoxPanel(), "South");
f.setLocation(200, 200);
f.pack();
f.setVisible(true);
}
private JPanel getCheckBoxPanel() {
checkValidate = new JCheckBox("validate");
checkValidate.setSelected(false);
checkReValidate = new JCheckBox("revalidate");
checkReValidate.setSelected(false);
checkRepaint = new JCheckBox("repaint");
checkRepaint.setSelected(false);
checkPack = new JCheckBox("pack");
checkPack.setSelected(false);
JButton addComp = new JButton("Add New One");
addComp.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
JButton b = new JButton();
b.setBackground(Color.red);
b.setBorder(new LineBorder(Color.black, 2));
b.setPreferredSize(new Dimension(600, 10));
panel.add(b);
makeChange();
System.out.println(" Components Count after Adds :" + panel.getComponentCount());
}
});
JButton removeComp = new JButton("Remove One");
removeComp.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
int count = panel.getComponentCount();
if (count > 0) {
panel.remove(0);
}
makeChange();
System.out.println(" Components Count after Removes :" + panel.getComponentCount());
}
});
JPanel panel2 = new JPanel();
panel2.add(checkValidate);
panel2.add(checkReValidate);
panel2.add(checkRepaint);
panel2.add(checkPack);
panel2.add(addComp);
panel2.add(removeComp);
return panel2;
}
private void makeChange() {
if (checkValidate.isSelected()) {
panel.validate();
}
if (checkReValidate.isSelected()) {
panel.revalidate();
}
if (checkRepaint.isSelected()) {
panel.repaint();
}
if (checkPack.isSelected()) {
f.pack();
}
}
public static void main(String[] args) {
AddComponentsAtRuntime makingChanges = new AddComponentsAtRuntime();
}
}
(may be due this ambiguity the description is changed in latest javaDoc )
JavaDoc 7 is NOT saying,
The validate method is used to cause a container to lay out its subcomponents again..
so its only laying the components, whereas you need a pack() again.
Note that pack() clearly says,
Causes this Window to be sized to fit the preferred size and layouts of its subcomponents.
The fundamental, yet subtle assumption at play here: layout and size are directly related, 1-to-1. This is not the case, and is a common assumption in Swing programming. Size is the result of layout and size constraints.
Layout is:
Within the space constraints you've specified
And given the components I have to fit within that space
Position those components in relation to one another given the specified strategy (BoxLayout, BorderLayout, etc.)
If the LayoutManager can fit the components you've given to it, without changing the overall size of the container, it will not alter the size of the container. A call to pack, on the other hand, is an explicit request to minimize the space being used. That's the basic reason you're seeing the results that you are.
Some things you might try:
Make sure you're setting a maximum size on your components/containers, which will force size constraints on components when re-doing the layout
Always call pack() as a habit
Try some of the suggestions regarding common layout issues
It's tricky with Swing, because you've got to understand the painting pipeline, the layout managers, and some details of the windowing system. When it comes to the Swing documentation (and all the methods and the several different ways there are to doing any one thing) I try to read the documentation with an "assume nothing" approach, meaning, "What's the minimum possible thing that this method's documentation implies that it might do," and unless you observe additional behavior, don't get tricked into thinking that it does more than that.
Finally, I would add that the job of LayoutManagers in general is not sizing of containers so much as it is to place components in some relation to one another, according to the layout strategy (this is discussed in additional detail here). The idea is that, with the proper LayoutManager, you specify a basic layout strategy, and as a result when you resize the window they LayoutManager will intelligently move the components around so that your UI continues to follow that overall strategy. In this way layouts are basically meant to be independent of the overall size of the space in which they work, so they try not to make assumptions about what space is available - instead they take the size they are given and try to do what makes sense. Unless you explicitly put size constraints on your components, you can't guarantee what size they will be.
That means, if the LayoutManager doesn't believe that it needs to resize something in order to make it fit its overall strategy, basically it won't resize it. A call to pack, on the other hand, is an explicit request to pack things together and remove extra space.