I have a JPanel with scrollbar and i want to add a lot of JLabels to it. But the scrollbar doesnt work . I can not use the scrollbar and even after the panel is full it doesn't scroll . Here is my code :
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class Scroll {
public static void main(String[] args) {
JPanel panel = new JPanel(new GridLayout(0,1));
JPanel p = new JPanel(new BorderLayout());
JScrollPane scroll = new JScrollPane(panel);
scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
p.add(scroll, BorderLayout.NORTH);
JButton but = new JButton("OK");
p.add(but, BorderLayout.SOUTH);
but.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
panel.add(new JLabel("Some random text"));
scroll.revalidate();
p.repaint();p.revalidate();
}
});
JFrame frame = new JFrame();
frame.setSize(800,200);
frame.setVisible(true);
frame.add(p);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
}
}
Your problem seems to lie with your layout managers. I think BorderLayout behaves strangely when you don't use the BorderLayout.CENTER position. I changed the line
p.add(scroll, BorderLayout.NORTH);
to
p.add(scroll, BorderLayout.CENTER);
Then, to make the text appear from the top instead of centering, I changed the layout manager for the panel component to a BoxLayout. From:
JPanel panel = new JPanel(new GridLayout(0, 1));
to
JPanel panel = new JPanel();
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
This seems to have given me the functionality you want. Let me know if this fixes your issues or not!
As already suggested, you should probably use JList or JTable to implement your use case.
Regarding the issue, this is because all BorderLayout constraints except of CENTER will expand to as much space as their components occupy, even if that means that they will expand out of the screen bounds (in your case the NORTH section expands to the south after each button click).
To solve this, explicitly specify the preferred size for the components which can grow indefinitely if you add them to a non-central panel section with BorderLayout:
scroll.setPreferredSize(new Dimension(-1, 100));
I use -1 for the width here to indicate that it is not important (I could use any other value), since it will be ignored by the layout manager anyway (with BorderLayout.NORTH the component is stretched horizontally to take all the available horizontal space).
Related
Well, actually I have a Layout problem in java Swing. I simply want to add a JPanel on the bottom of a Frame - a coding snipplet that might be done with every web based language in about 5 Minutes. Not so in Java. I tried to add a jPanel to a jFrame, that Contains a jContentPane, set the size of the jPanel to what I need and to repaint and revalidate the jFrame, as well as setting the LayOutManager to null.
Java shows me in this case a full-width jPanel, that fills my whole jFrame.
Therefore I tried another approach: I divided my jPanel in a fully transparent jPanel on top and a 20%opaque jPanel on the bottom. Still it didn't work out as expected.
Since then I tried to resize the child jPanels of my new Panel and the Panel as well and tried to repaint and revalidate the jFrame. Without any effect.
Despite of my efforts, java still shows me a full sized 20%opaque jPanel on the whole jFrame, that now contains another 20%opaque jPanel on Top.
I know that this whole problem is caused by the LayoutManager, Java useless per Default. However, it is not an option to set the LayoutManager to null or even change the LayoutManager of our jFrame, because that would lead us to refactor the whole functionality of our tiny app we worked on for several weeks.
public void showUndoPanel() {
System .out.println("Show Undo Panel");
JPanel myPanel = new JPanel(null);
JPanel glassPanel = new JPanel();
JPanel ContentPanel = new JPanel();
JLabel myJLabel = new JLabel("Great Job!");
myPanel.setBackground(new Color(255,122,122,100));
glassPanel.setSize(650, 550);
glassPanel.setBackground(new Color(255,122,122,100));
myPanel.add(glassPanel);
ContentPanel.setSize(650, 30);
ContentPanel.setBackground(new Color(255,122,122,20));
ContentPanel.add(myJLabel);
myPanel.revalidate();
myPanel.repaint();
undoPanel = myPanel;
myJFrame.add(undoPanel);
myJFrame.revalidate();
}
What I expected:
What it actually does:
Well, I solved the problem by using a BoxLayoutManager and a RigidArea. In case if anyone else may encounter that problem again in the future, I decided to provide the code for this simple solution.
public void showUndoPanel() {
System .out.println("Show Undo Panel");
JPanel myPanel = new JPanel(null);
JPanel glassPanel = new JPanel();
JPanel ContentPanel = new JPanel();
JLabel myJLabel = new JLabel("Great Job!");
myPanel.setBackground(new Color(255,255,255,0));
myPanel.setLayout(new BoxLayout(myPanel, BoxLayout.PAGE_AXIS));
glassPanel.setSize(650, 650);
glassPanel.setBounds(0,0,650,550);
glassPanel.setBackground(new Color(255,122,122,0));
myPanel.add(glassPanel);
myPanel.add(Box.createRigidArea(new Dimension(0,450)));
ContentPanel.setSize(650, 30);
ContentPanel.setBounds(0,750,650,30);
ContentPanel.setBackground(new Color(255,122,122,20));
ContentPanel.add(myJLabel);
myPanel.add(ContentPanel);
myPanel.revalidate();
myPanel.repaint();
undoPanel = myPanel;
myJFrame.add(undoPanel);
myJFrame.revalidate();
}
Now it behaves as expected:
BorderLyout would make it easier to implement.
Note the comments in the following mre:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class Main {
private static JFrame myJFrame;
public static void main(String[] args) {
myJFrame = new JFrame();
myJFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
myJFrame.setLocationRelativeTo(null);
showUndoPanel();
myJFrame.pack();
myJFrame.setVisible(true);
}
public static void showUndoPanel() {
JPanel myPanel = new JPanel();
myPanel.setBackground(new Color(255,255,255,0));
myPanel.setLayout(new BorderLayout());
JPanel glassPanel = new JPanel(); //uses FlowLayout by default
//glassPanel.setSize(650, 650); //use preferred size
glassPanel.setPreferredSize(new Dimension(650, 650));
//glassPanel.setBounds(0,0,650,550); //no need to set bounds. bounds are set by the layout manager
glassPanel.setBackground(new Color(255,122,122,0));
myPanel.add(glassPanel, BorderLayout.CENTER);
JPanel contentPanel = new JPanel(); //uses FlowLayout by default
//contentPanel.setSize(650, 30);//use preferred size
contentPanel.setPreferredSize(new Dimension(650, 30));
//contentPanel.setBounds(0,750,650,30); //no need to set bounds. bounds are set by the layout manager
contentPanel.setBackground(new Color(255,122,122,20));
JLabel myJLabel = new JLabel("Great Job!");
contentPanel.add(myJLabel);
myPanel.add(contentPanel, BorderLayout.SOUTH);
myJFrame.add(myPanel);
}
}
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 am trying to add JScrollPane to my large JTextArea, but whenever I include the JScrollPane code, my whole JTextArea disappears.
public myGUI() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 1174, 656);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
contentPane.setVisible(true);
JTextArea textArea_1 = new JTextArea();
textArea_1.setBounds(203, 5, 869, 440);
textArea_1.setEditable(true);
textArea_1.setVisible(true);
contentPane.add(textArea_1);
JScrollPane scroll = new JScrollPane (textArea_1);
scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scroll.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
contentPane.add(scroll);
}
Several problems with your code:
You're trying to add a component, here your JTextArea called textArea_1, to multiple containers, here the contentPane and the JScrollPane. You can't do this in Swing as a component can be added to only one component. Add it only to the JScrollPane and not to the contentPane, and then add the scroll pane to the GUI.
You're constraining the size of your JTextArea via setBounds which almost guarantees that the JScrollPane will not work since doing this prevents the JTextArea from expanding when it holds more text than is shown. Instead set the JScrollPane's rows and columns properties and not its bounds. This will be the number of rows and columns that it should display within the scrollpane
You're using null layouts but not specifying the size of the JScrollPane, and so it defaults to a size of [0, 0] -- and this is why your JTextArea disappears. Null layouts require complete specification of all component sizes and positions.
You're using null layouts to set up your GUI. While null layouts and setBounds() might seem to Swing newbies like the easiest and best way to create complex GUI's, the more Swing GUI'S you create the more serious difficulties you will run into when using them. They won't resize your components when the GUI resizes, they are a royal witch to enhance or maintain, they fail completely when placed in scrollpanes, they look gawd-awful when viewed on all platforms or screen resolutions that are different from the original one.
For example:
import java.awt.BorderLayout;
import java.awt.Font;
import java.awt.GridLayout;
import javax.swing.*;
#SuppressWarnings("serial")
public class MyGuiPanel extends JPanel {
// some row and column values for our JTextArea
private static final int TXT_AREA_ROWS = 25;
private static final int TXT_AREA_COLS = 80;
// create the JTextArea, passing in the rows and columns values
private JTextArea textArea = new JTextArea(TXT_AREA_ROWS, TXT_AREA_COLS);
public MyGuiPanel() {
// create the JScrollPane, adding our JTextArea
JScrollPane scroll = new JScrollPane(textArea);
scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scroll.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
// lets add some buttons to the bottom of the GUI just for fun
JPanel buttonPanel = new JPanel(new GridLayout(1, 0, 5, 0));
buttonPanel.add(new JButton("Save"));
buttonPanel.add(new JButton("Open"));
buttonPanel.add(new JButton("Delete"));
buttonPanel.add(new JButton("Exit"));
// let's add a title to the top:
JLabel title = new JLabel("This is my Applications's Title", SwingConstants.CENTER);
title.setFont(title.getFont().deriveFont(Font.BOLD, 24)); // and make
// the text
// *BIG*
// use a BorderLayout for our GUI
setLayout(new BorderLayout(5, 5));
setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
add(scroll, BorderLayout.CENTER); // add the scrollpane to the center
add(buttonPanel, BorderLayout.PAGE_END); // the button panel to the
// bottom
add(title, BorderLayout.PAGE_START); // and the title JLabel to the top
}
private static void createAndShowGui() {
// create our GUI JPanel
MyGuiPanel mainPanel = new MyGuiPanel();
// create a JFrame to add it to
JFrame frame = new JFrame("My GUI");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel); // add the GUI to the JFrame
frame.pack(); // tell the layout managers to do their work
frame.setLocationByPlatform(true);
frame.setVisible(true); // display the GUI
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
}
Also, if your program extends JFrame, understand that you are painting yourself in a corner by doing this, forcing you to create and display JFrames, when often more flexibility is called for. In fact, I would venture that most of the Swing GUI code that I've created and that I've seen does not extend JFrame, and in fact it is rare that you'll ever want to do this. More commonly your GUI classes will be geared towards creating JPanels, which can then be placed into JFrames or JDialogs, or JTabbedPanes, or swapped via CardLayouts, wherever needed. This will greatly increase the flexibility of your GUI coding.
You do not need setBounds for your JTextArea. Because you are using a null layout and the JScrollPane has no bounds, nothing shows up. Your JTextArea is also added to two places which would cause some problems. I would recommend any of swings layout managers. As an example using BorderLayout which is one of the easiest managers:
public mygui() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
setSize(700, 500);
setLayout(new BorderLayout());
JTextArea textArea_1 = new JTextArea();
textArea_1.setEditable(true);
JScrollPane scroll = new JScrollPane(textArea_1);
scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scroll.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
add(scroll, BorderLayout.CENTER);
}
What kind of layout should I use to create a page Like this:
It should be resizable
It has two main panels Right and Left?
Extra space will be given to the 'Main Text' text area, and extra height will be given to the button panel while centering them.
import java.awt.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
public class EndOfLineButtonLayout {
public static void main(String[] args) {
Runnable r = new Runnable() {
#Override
public void run() {
// the GUI as seen by the user (without frame)
JPanel gui = new JPanel(new BorderLayout());
gui.setBorder(new EmptyBorder(2, 3, 2, 3));
JPanel textPanel = new JPanel(new BorderLayout(5,5));
textPanel.add(new JScrollPane(new JTextArea("Top Text",3,20)),
BorderLayout.PAGE_START);
textPanel.add(new JScrollPane(new JTextArea("Main Text",10,10)));
gui.add(textPanel, BorderLayout.CENTER);
JPanel buttonCenter = new JPanel(new GridBagLayout());
buttonCenter.setBorder(new EmptyBorder(5,5,5,5));
JPanel buttonPanel = new JPanel(new GridLayout(0,1,5,5));
for (int ii=1; ii<6; ii++) {
buttonPanel.add(new JButton("Button " + ii));
}
// a component added to a GBL with no constraint will be centered
buttonCenter.add(buttonPanel);
gui.add(buttonCenter, BorderLayout.LINE_END);
JFrame f = new JFrame("Demo");
f.add(gui);
// Ensures JVM closes after frame(s) closed and
// all non-daemon threads are finished
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
// See http://stackoverflow.com/a/7143398/418556 for demo.
f.setLocationByPlatform(true);
// ensures the frame is the minimum size it needs to be
// in order display the components within it
f.pack();
// should be done last, to avoid flickering, moving,
// resizing artifacts.
f.setVisible(true);
}
};
// Swing GUIs should be created and updated on the EDT
// http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html
SwingUtilities.invokeLater(r);
}
}
You can use gridbag layout, try using netbeans, I have tried it and found really usefull.
Once you create it with netbeans you can use the same and build infact any kind of layout.
best of luck with other solutions.
p.s. border layout is perfect for your requirement, but I mentioned this just in case you would like to do lot more .
I would use BorderLayout.
Create Three JPanels and add them to a JFrame as follows:
public class YourClass extends JFrame{
//code here
this.setLayout(new BorderLayout());
this.add(TopPanel, BorderLayout.NORTH);
this.add(RightPanel, BorderLayout.EAST);
this.add(MainPanel, BorderLayout.CENTER);
this.pack();
this.setVisible(true);
The two main panels would be placed inside a main JPanel using a BorderLayout. The left panel would be placed using BorderLayout.CENTER, and the right panel would be placed using BorderLayout.LINE_END.
The left panel would use a BoxLayout, Y axis to separate the two JPanels within the left panel.
The right buttons panel would use a GridBagLayout. This sizes the buttons the same and allows you to use Insets to add some spacing to the buttons.
The buttons would be spaced from the top to the bottom of the right buttons panel. If you want all the buttons towards the top of the right buttons panel, you would put the right buttons panel inside of another JPanel using a FlowLayout.
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)