I am programming a multiplication app for very large integers, I need to update every sigle step of the multiplication in a Swing component ( I created a JPane extended class with a JTextArea in it, then add it to the JFrame inside a ScrollPane). The issue is that this Swing component only updates once the multiplication algorithm is done. I tried using a Thread that would call repaint method of the Pane every 10 ms, but it did not work. The next is a sample of the problem.
This is the main Frame class:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
public class Frame extends JFrame implements ActionListener{
private Console console;
private JButton calculate;
private Calculator calculator;
public Frame(){
console=new Console();
calculate=new JButton("Calculate");
calculate.addActionListener(this);
calculate.setActionCommand("");
calculator=new Calculator(this);
this.setLayout(new BorderLayout());
this.add(console,BorderLayout.CENTER);
this.add(calculate, BorderLayout.NORTH);
this.setTitle("Frame");
this.setVisible(true);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(new Dimension(500,500));
this.setLocationRelativeTo(null);
}
public void writeOnConsole(String txt){
console.write(txt);
}
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
if(e.getActionCommand().equals("")){
console.clear();
calculator.calculate();
}
}
public static void main(String[] args) {
new Frame();
}
}
This is the Console Class
import java.awt.BorderLayout;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.border.TitledBorder;
public class Console extends JPanel{
private JTextArea area;
public Console(){
this.setBorder(new TitledBorder("Console:"));
area=new JTextArea();
this.setLayout(new BorderLayout());
JScrollPane scroll=new JScrollPane(area);
this.add(scroll,BorderLayout.CENTER);
}
public void clear(){
area.setText("");
}
public void write(String txt){
area.append(txt+"\n");
}
}
Finally, this is the Calculator class (the one responsible for calling the writing)
public class Calculator {
private Frame parent;
public Calculator(Frame f){
parent=f;
}
public void calculate(){
for (int i = 0; i <= 1000000; i++) {
parent.writeOnConsole("Iteration "+i);
}
}
}
Note that if you run the program, the GUI will freeze until the Calculator class is done with the loop.
if you have a layout like a BorderLayout and you want to update it inside the JFrame do as bellow
JFrame frame = new JFrame();
BorderLayout layout = new BorderLayout();
layout.layoutContainer(frame.getContentPane());// use the frame as the border layout container
else you can use JFrame pack() method. The pack method packs the components within the window based on the component’s preferred sizes. it's not for updating but it updates the JFrame which is kind of a trick
JFrame frame = new JFrame();
//change the components dynamically
frame.pack();
or use Container methdod validate(). Validating a container means laying out its subcomponents. Layout-related changes, such as setting the bounds of a component, or adding a component to the container.
JFrame frame = new JFrame();
Container container = frame.getContentPane();
container.validate();
or if you want to update an specific component use
Component component = new JPanel();
component.repaint();
If this component is a lightweight component, repaint() method causes a call to this component's paint method as soon as possible .
or if you want for example numerous changes happen one by one dynamically then you could use the code below which is completely different from the things i said above. for that you could use platform.runlater() inside another thread which deals with everything that is about to change in realtime
new Thread(new Runnable()
{
#Override
public void run()
{
Platform.runLater(new Runnable()//use platform.runlater if you are using javafx
{
#Override
public void run()
{
try
{Thread.sleep(50);}catch(Exception e){}//use it in for loop where changes happen
//do some realtime change of components
}
});
}).start();
your Console class would be
import java.awt.BorderLayout;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.border.TitledBorder;
public class Console extends JPanel{
private JTextArea area;
public Console(){
this.setBorder(new TitledBorder("Console:"));
area=new JTextArea();
this.setLayout(new BorderLayout());
JScrollPane scroll=new JScrollPane(area);
this.add(scroll,BorderLayout.CENTER);
}
public void clear(){
area.setText("");
}
public void write(String txt){
area.append(txt+" "+"\n");
}
}
and the Calculator class is
public class Calculator {
private Frame parent;
public Calculator(Frame f){
parent=f;
}
public void calculate(){
new Thread(new Runnable() {
#Override
public void run()
{
for (int i = 0; i <= 100; i++) {
try
{
Thread.sleep(50);
}
catch(Exception e)
{
e.printStackTrace();
}
parent.writeOnConsole("Iteration "+i);
}
}
}).start();
}
}
as you can see i used another thread to do the changes
try the update method to call paint method for maintain every change
Related
I have a JPanel in a JScrollPane.
The JPanel contains multiple JTextAreas vertically.
I like to keep the scroll of the scrollpane to the top whenever the page is refreshed.
Currently, the scroll always starts from the bottom.
this is my current code and it doesn't work..
panel.invalidate();
panel.revalidate();
panel.repaint();
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
((JPanel) panel).setLocation(new Point(0, 0));
}
});
I've also tried adding this code below to scrollpane, but it doesn't work..
scrollPanel.getViewport().setViewPosition( new Point(0, 0) );
I've looked into other stackoverflow questions and they use Jtextarea inside Jscrollpane (they solved it using setCaretPosition(0), however I can't use the same function to the panel). In my case, there is an extra layer.
How can I solve this..?
EDIT**
Based on advice from Pavlo Viazovskyy, I've also tried this below and it still doesn't work for me.. :(
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
scrollPane.getVerticalScrollBar().setValue(0);
}
});
Thank you very much for all the comments.
sorry I didn't give a full proper example in the question as there were too many different classes involved..
In my case, textareas inside Panel inside ScrollPane, I made the scroll to the top by default by using setViewPosition method to scrollPane in the invokelater method.
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
scrollPane.getViewport().setViewPosition( new Point(0, 0) );
}
});
For when you don't have direct access to the JScrollPane, you can simply use JComponent#scrollRectToVisible
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
public class ScrollTest {
public static void main(String[] args) {
new ScrollTest();
}
public ScrollTest() {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new JFrame("Test");
frame.add(new JScrollPane(new BigPane()));
frame.setSize(200, 200);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class BigPane extends JPanel {
public BigPane() {
setLayout(new BorderLayout());
JButton scroll = new JButton("Scroll to top");
add(scroll, BorderLayout.SOUTH);
scroll.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
scrollRectToVisible(new Rectangle(0, 0, 1, 1));
}
});
}
#Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
}
}
Yes, you could walk the component hierarchy till you found a JViewport, but this method does it for you.
Just remember though, the Rectangle is relative to the component which called the method, so if I used the JButton instead, it would try and make the JButton visible, not the panel
I've made a JFrame with Diferent JButtons and i'd like to get an image from another class. Any ideas? Or how draw on the same class but on the action performed?
Because it doesnt let me to do any drawings...my complier always gives me error messages
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import javax.swing.*;
public class red extends JFrame {
public JButton b;
public JButton b1;
public JButton b2;
public JButton b3;
public JButton b4;
public static Image p;
public static Graphics g;
public red() throws IOException {
gui1 x = new gui1();
setTitle(" ");
setSize(1200,700);
setLayout(null);
setDefaultCloseOperation(EXIT_ON_CLOSE);
b= new JButton("click");
b1= new JButton();
b.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent e0){
b1.setBounds(0, 0, 200, 200);
b.show(false);
add(x);
}
});
b.setBounds(0, 0, 100, 100);
add(b1);
add(b);
setVisible(true);
}
public static void main(String[] args) throws IOException {
red k = new red();
}
}
import java.awt.*;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
public class gui1 extends Canvas {
public static Image p;
public void paint(Graphics g){
g.drawImage(p, 700, 200, 100, 100, this);
}
{
try {
p= ImageIO.read(new File("Lighthouse.jpg"));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
Phew! I see A LOT of errors in your code (even after I corrected the compilation errors):
You're not following the Java naming conventions:
Class names should be nouns, in mixed case with the first letter of each internal word capitalized
while red is a noun it should be more descriptive and be capitalized. The same goes for gui1
You're extending JFrame which in plain english would say: red is a JFrame, you should really avoid this and create your GUI based on JPanels instead... see Java Swing using extends JFrame vs callint it inside of class
You're setting size (a REAAAAAAALLY big one window for the JButton sizes you're using), instead use pack()
You're using null-layout, while pixel-perfect GUIs might seem like the easiest way to create complex GUIs for Swing newbies, the more you use them the more problems related to this you'll find in the future, they are hard to maintain and cause random problems, they don't resize, etc. Please read Null layout is evil and Why is it frowned upon to use a null layout in Swing? for more information about why you should avoid its use and why you should change your GUI to work with Layout Managers along with Empty Borders for extra spacing between components.
You're making use of a deprecated method JFrame#show() you should be using JFrame#setVisible(...) instead.
Related to point #4, you shouldn't be calling setBounds(...) method, but let that calculations to the layout managers.
You're not placing your program on the Event Dispatch Thread (EDT), Swing is not thread safe, you can fix this by changing your main() method as follows:
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
//Your constructor here
}
});
}
You're mixing AWT and Swing components, instead of using AWT's Canvas use Swing's JPanel which has more functionality and support.
Images will become embedded resources once they're packaged in a JAR file, so it's wise to start treating them as if they already were, not as external files as shown in the embedded-resource tag.
Once you change from Canvas to JPanel you should override its paintComponent(...) method and not paint(...) and call it's super.paintComponent(g) method as the first line, also don't forget to add the #Overrides annotation. See the tutorial on Swing custom painting.
You're abusing the use of static keyword, see how does the static keyword works?
After seeing all the above errors I recommend you to go back and Learn the basics of the language before starting with a graphical environment which will only add more difficulty to your learning.
From what I understand you want to draw an image on a button click, if that's the case then you can wrap your image in a JLabel and add that JLabel to a JPanel which then is added to a parent JPanel which is later added to the JFrame:
As you can see in the GIF above, the icon is displayed after user presses the button.
Obviously this can be improved for the GUI to be more "attractive" with combinations of layout managers and empty borders as stated before.
This was done with the following code:
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BoxLayout;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class ImageDrawingFromOneClassToAnother {
private JFrame frame;
private JPanel pane;
private JPanel leftPane;
private JPanel rightPane;
private ImageIcon icon;
private JButton button;
private JLabel label;
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new ImageDrawingFromOneClassToAnother().createAndShowGui();
}
});
}
public void createAndShowGui() {
frame = new JFrame(getClass().getSimpleName());
icon = new ImageIcon(this.getClass().getResource("king.png")); //Read images as if they were already embedded resources
button = new JButton("Draw image");
label = new JLabel(""); //Create an empty label
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
label.setIcon(icon); //On button click, we set the icon for the empty label
}
});
pane = new JPanel() {
#Override
public Dimension getPreferredSize() {
return new Dimension(300, 200); //Set a size for the main panel
}
};
pane.setLayout(new GridLayout(1, 2)); //The main panel
leftPane = new JPanel(); //The button panel
leftPane.setLayout(new BoxLayout(leftPane, BoxLayout.PAGE_AXIS));
leftPane.add(button);
rightPane = new JPanel(); //The panel where the image will be drawn
rightPane.add(label);
//We add both (button and image) panels to the main panel
pane.add(leftPane);
pane.add(rightPane);
frame.add(pane); //Add the main panel to the frame
frame.pack(); //Calculate its preferred size
frame.setVisible(true); //Set it to be visible
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
In my application, I have a main frame that holds a base panel. The base panel will hold 4 sub-panels. So lets say, the first sub panel appears, do a process on a data, then it must let the second sub panel to appear and also pass the result data to it. The the second sub panel must do another calculation and pass it to third one and so on.
I used card Layout for this, but I do not know how to make panels visible one after end of the previous panel's work.
Here is a simplified version:
public class LittleCardLayout{
public static void main(String[] args) {
new LittleCardLayout();
}
public LittleCardLayout(){
JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new BasePane());
frame.setSize(800, 500);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
Base Panel:
public class BasePane extends JPanel{
public BasePane() {
setLayout(new BorderLayout());
CardLayout cl = new CardLayout();
JPanel mainView = new JPanel(cl);
mainView.add(new JPanel(), "empty");
mainView.add(new TopPanel(), "toppanel");
cl.show(mainView, "toppanel");
add(mainView, BorderLayout.NORTH);
}
}
Sub Panel 1:
public class TopPanel extends JPanel {
int myValue = 23;
int newVal;
public TopPanel(){
JButton btn = new JButton("Load Value");
btn.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
newVal= 23-3;
add(new BottomPanel(newVal), "toppanel");
}
});
add(btn, BorderLayout.NORTH);
}
}
Sub Panel 2:
public class BottomPanel extends JPanel {
int num;
JLabel myLabel = new JLabel();
BottomPanel(int num){
this.num = num;
num = num*5;
myLabel.setText(Integer.toString(num));
add(myLabel);
}
}
it must work like a step by step process.
So any idea to pass data from one panel to another and make them visible after one another?
Also is it the right way to make such a step by step process, or there is a better idea?
As each panel completes it's processing, it should send a notification back to the parent panel, telling it that it has finished. The parent panel would then decide what to do.
The child panel should NEVER make navigation decisions...
This is pretty basic example of the concept.
It uses two interfaces (I'm a stickler for coding to interface and limiting exposure of implementation details), a Processor which processes stuff and a ProcessListener which is used to notify the registered listener that the Processor has finished.
import java.awt.CardLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new BasePane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class BasePane extends JPanel {
private List<Processor> order;
private CardLayout cardLayout;
private ProcessListener processListener;
public BasePane() {
cardLayout = new CardLayout();
setLayout(cardLayout);
order = new ArrayList<>(4);
processListener = new ProcessListener() {
#Override
public void processingComplete(Processor source) {
int nextIndex = order.indexOf(source) + 1;
System.out.println(nextIndex);
if (nextIndex < order.size()) {
Processor next = order.get(nextIndex);
System.out.println(next.getName());
cardLayout.show(BasePane.this, next.getName());
next.startProcessing();
}
}
};
createProcessor("Meaning of life");
createProcessor("Apple Pi");
createProcessor("Thermal dynamics");
createProcessor("Microsoft Word");
Processor first = order.get(0);
cardLayout.show(BasePane.this, first.getName());
first.startProcessing();
}
protected Processor createProcessor(String name) {
ProcessorPane pane = new ProcessorPane(name);
pane.setProcessListener(processListener);
add(pane, name);
order.add(pane);
return pane;
}
}
public interface Processor {
public void setProcessListener(ProcessListener listener);
public ProcessListener getProcessListener();
public void startProcessing();
public String getName();
}
public interface ProcessListener {
public void processingComplete(Processor source);
}
public class ProcessorPane extends JPanel implements Processor {
private ProcessListener listener;
public ProcessorPane(String name) {
setName(name);
setLayout(new GridBagLayout());
add(new JLabel(name));
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
#Override
public void setProcessListener(ProcessListener listener) {
this.listener = listener;
}
#Override
public void startProcessing() {
Timer timer = new Timer(1000, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
getProcessListener().processingComplete(ProcessorPane.this);
}
});
timer.setRepeats(false);
timer.start();
}
#Override
public ProcessListener getProcessListener() {
return listener;
}
}
}
The basic concept could be expanded so that Processor had a getValue and setValue (for example) methods which would allow the controller (in this case the BasePane) to pass information from one Processor to another
This is just the implementation based on your current approach. I might be possible to use a different approach which separated the UI from the processing, so that you had a "processing controller" which was controlling the processing work flow and passing notifications back to the UI (or registered listeners) about it's current state of operations.
Equally, you could use the above idea, but instead use polling, periodically requesting information from the "processing controller"...just as some ideas of the top of the head
I'm sure someone has asked this question before, but my google-fu is not strong today.
I have a JFrame that uses a CardLayout as its manager. How do I run a "Start" method when I switch to each JPanel without using a switch?
The code I use to add the frames to the layout is:
/**
* Adds JPanels to the Card Layout.
* #param panel is the JPanel to add to the layout.
* #param windowName is the identifier used to recognise the Panel.
*/
public final void addToCards(final JPanel panel, final WindowNames windowName) {
view.getBasePanel().add(panel, windowName.getValue());
}
The code I use to switch the layout is:
/**
* Method to change the JPanel currently visible on the BasePanel.
* #param windowName is the name of the JPanel to change to.
*/
public final void changePanel(final WindowNames windowName) {
view.getCardLayout().show(view.getBasePanel(), windowName.getValue());
}
Currently I have an ActionListener set that will call the switch code, but I can't work out how to call the "Start" method within the screen that it will be switching to.
I have an interface setup for each of the JPanels so that the method name will be identical in each.
You can just use a ComponentListener for the panel(s). When the panel becomes the view of the CardLayout, it will fire a component event and handled by componentShown in your listener (as well as the panel taken out of view, handling the componentHidden). Call your start() method there. This way you don't have to explicitly call the start() when the panel changes, as it be called for you.
See How to Write Component Listeners for more details.
Here is a simple example.
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Main {
private static final String PANEL_A = "panelA";
private static final String PANEL_B = "panelB";
CardLayout layout = new CardLayout();
JPanel panel = new JPanel(layout);
ComponentListenerPanel p1 = new ComponentListenerPanel(PANEL_A);
ComponentListenerPanel p2 = new ComponentListenerPanel(PANEL_B);
JButton b1 = new JButton(PANEL_A);
JButton b2 = new JButton(PANEL_B);
public Main() {
panel.add(p1, PANEL_A);
panel.add(p2, PANEL_B);
b1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
show(PANEL_A);
}
});
b2.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
show(PANEL_B);
}
});
JPanel buttonPanel = new JPanel();
buttonPanel.add(b1);
buttonPanel.add(b2);
JFrame frame = new JFrame();
frame.add(panel);
frame.add(buttonPanel, BorderLayout.PAGE_END);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public void show(String panelName) {
layout.show(panel, panelName);
}
private class ComponentListenerPanel extends JPanel {
private String panelName;
public ComponentListenerPanel(String panelName) {
this.panelName = panelName;
addComponentListener(new ComponentAdapter() {
#Override
public void componentHidden(ComponentEvent evt) {
stop();
}
#Override
public void componentShown(ComponentEvent evt) {
start();
}
});
}
public void start() {
System.out.println(panelName + " started");
}
public void stop() {
System.out.println(panelName + " stopped");
}
#Override
public Dimension getPreferredSize() {
return new Dimension(300, 300);
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new Main();
}
});
}
}
Note you haven't actually said where the start method is, so this code/answer is just assuming you have some start method in custom panel. Hope I guessed right. In the future, or even now, you should always post an MCVE so that we don't have to do all this guessing.
I have an interface setup for each of the JPanels so that the method name will be identical in each
So then the problem is getting the current panel that is visible when the panels are swapped so you can invoke the method.
Check out Card Layout Focus for a class that extends CardLayout to provide a few helper methods to add additional functionality for the CardLayout. You would use the getCurrentCard() method.
So your changePane(...) method might be something like:
public final void changePanel(final WindowNames windowName) {
//view.getCardLayout().show(view.getBasePanel(), windowName.getValue());
RXCardLayout layout = view.getCardLayout();
layout.show(view.getBasePanel(), windowName.getValue());
MyInterface panel = (MyInterface)layout.getCurrentCard();
panel.someMethod(...);
}
Of course you would also need to use the RXCardLayout as the layout manager for your main panel.
Working in Java: I have a JFrame class, and separate classes for my two JPanels that are added to the JFrame. One of the JPanel classes has some buttons in it, which can interact with each other(when I click on one button, it can disable another button). However, I can't figure out how to get the button to call a method in the other JPanel (written in a separate class).
So, my program look like this:
JFrame
Jpanel1
Jpanel2 - This class has my buttons in it, I'm trying to get them to interact with the JPanel1 object.
Any tips appreciated, thanks!
One way to do this is to pass an instance of (to use your terminology) Jpanel1 into Jpanel2. This doesn't have to be done in the constructor, you can have a setConnectedPanel(JPanel) method, for example.
Here's some code that demonstrates what you want to do:
MyFrame.java
import java.awt.GridLayout;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
public class MyFrame extends JFrame {
public MyFrame() {
ReactionPanel rp = new ReactionPanel();
ActionPanel ap = new ActionPanel(rp);
setLayout(new GridLayout(2, 1));
add(ap);
add(rp);
pack();
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new MyFrame();
}
});
}
}
ActionPanel.java
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JPanel;
public class ActionPanel extends JPanel implements ActionListener {
private ReactionPanel rp;
private JButton button;
public ActionPanel(ReactionPanel rp) {
this.rp = rp;
button = new JButton("Click");
button.addActionListener(this);
this.add(button);
}
#Override
public void actionPerformed(ActionEvent e) {
if(e.getSource().equals(button)) {
rp.react();
}
}
}
ReactionPanel.java
import javax.swing.JLabel;
import javax.swing.JPanel;
public class ReactionPanel extends JPanel {
private JLabel label;
public ReactionPanel() {
label = new JLabel("PING");
this.add(label);
}
public void react() {
if(label.getText().equals("PING")) {
label.setText("PONG");
} else {
label.setText("PING");
}
}
}
As you can see, I tend to override all of my JFrames/JPanels when I write Swing GUIs as I find it easier and more flexible but YMMV.