I have a frame which starts a swingTimer to perform a periodic task. The problem is when I close the frame, the task still continues. I want the swingTimer to stop if the close button is pressed.
I have tried specifying EXIT_ON_CLOSE and DISPOSE_ON_CLOSE but these do not work. Does someone know what I should do?
Thanks
Swing Timer has a stop method. You can always call that if the "frame" (JFrame??) ends via a WindowListener.
Also, per my tests, the Timer should stop on its own if the EDT stops. For example:
import java.awt.event.*;
import javax.swing.*;
public class StopTimer extends JPanel {
private static final float FONT_SIZE = 32;
private Timer myTimer;
private JLabel timerLabel = new JLabel("000");
private int count = 0;
public StopTimer() {
timerLabel.setFont(timerLabel.getFont().deriveFont(FONT_SIZE));
add(timerLabel);
int timerDelay = 1000;
myTimer = new Timer(timerDelay , new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
count++;
timerLabel.setText(String.format("%03d", count));
System.out.println("count: " + count);
}
});
myTimer.start();
}
private static void createAndShowUI() {
JFrame frame = new JFrame("StopTimer");
frame.getContentPane().add(new StopTimer());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
createAndShowUI();
}
});
}
}
If this doesn't help you, then do what I've done: post a small compilable and runnable program that demonstrates your problem.
Related
I have been coding for a card game and cannot get my method to wait for a button to be pressed.
The general code goes like this. When I run the code, doTask() has a segment where it needs to wait for a button to be pressed. However, the method does not wait for the button and just loops through.
I am currently thinking to have a while loop with a boolean (buttonIsPressed) which will be triggered true in actionPerformed(e). However, is there a simpler way to do this?
Any help would be appreciated.
Thank you.
public class Test {
public Test()
{
// all vars instantiated
while (!(taskLeft==0))
{
doTask();
taskLeft--;
}
}
private class Handler implements ActionListener
{
public void actionPerformed(ActionEvent arg0) {
// update information in doTask()
}
}
}
Yours is a classic XY Problem where you ask how to solve a specific code problem when the best solution is to use a completely different approach. You're thinking of how do I code this event-driven GUI program to work as a linear console program, and that's not how you should approach this. Instead look at changing object state and basing response of the object to events based on its state.
So get rid of the while loop, and instead do your task when the button is pushed based on the state of the GUI. The details of any solution will depend on the details of your problem, something you may wish to share with us.
So for instance, here taskLeft represents a "state" of the TaskEx object, and your Handler's response will depend on the state of this variable.
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class TaskEx extends JPanel {
private int taskLeft = 10;
public void doTask() {
//
}
private class Handler implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
if (taskLeft > 0) {
doTask();
taskLeft--;
}
}
}
}
An actually functioning example:
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import javax.swing.*;
#SuppressWarnings("serial")
public class TaskEx extends JPanel {
private int taskLeft = 10;
private JLabel taskCountLabel = new JLabel(String.valueOf(taskLeft));
public TaskEx() {
JPanel northPanel = new JPanel();
northPanel.add(new JLabel("Tasks Left:"));
northPanel.add(taskCountLabel);
JPanel centerPanel = new JPanel();
centerPanel.add(new JButton(new Handler("Push Me")));
setLayout(new BorderLayout());
add(northPanel, BorderLayout.PAGE_START);
add(centerPanel, BorderLayout.CENTER);
}
public void doTask() {
taskCountLabel.setText(String.valueOf(taskLeft));
}
private static void createAndShowGui() {
TaskEx mainPanel = new TaskEx();
JFrame frame = new JFrame("Task Example");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
createAndShowGui();
});
}
private class Handler extends AbstractAction {
public Handler(String name) {
super(name);
putValue(MNEMONIC_KEY, (int) name.charAt(0));
}
#Override
public void actionPerformed(ActionEvent e) {
if (taskLeft > 0) {
taskLeft--;
doTask();
}
}
}
}
I'm having some trouble with this piece of code.
I'm starting a timer with a random number, and I want to update a JLabel with the countdown, every second. But I haven't figured out how to do so, since the only listener the timer triggers is at the end of it (that I know).
here's the code:
int i = getTimer(maxWait);
te1 = new Timer(i, this);
label.setText(i+"");
te1.start();
...
public int getTimer(int max){
Random generator = new Random();
int i = generator.nextInt(max);
return i*1000;
}
...
public void actionPerformed(ActionEvent ev){
if(ev.getSource() == te1){
label.setText(i+"");
te1.stop();
}
}
I don't really understand your question why you are using the Random, but here are some observations:
I want to update a JLabel with the countdown, every second.
Then you need to set the Timer to fire every second. So the parameter to the Timer is 1000, not some random number.
Also, in your actionPerformed() method you stop the Timer the first time it fires. If you are doing a count down of some kind then you would only stop the Timer when the time reaches 0.
Here is a simple example of using a Timer. It just updates the time every second:
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.Timer;
public class TimerTime extends JPanel implements ActionListener
{
private JLabel timeLabel;
public TimerTime()
{
timeLabel = new JLabel( new Date().toString() );
add( timeLabel );
Timer timer = new Timer(1000, this);
timer.setInitialDelay(1);
timer.start();
}
#Override
public void actionPerformed(ActionEvent e)
{
//System.out.println(e.getSource());
timeLabel.setText( new Date().toString() );
}
private static void createAndShowUI()
{
JFrame frame = new JFrame("TimerTime");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add( new TimerTime() );
frame.setLocationByPlatform( true );
frame.pack();
frame.setVisible( true );
}
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowUI();
}
});
}
}
If you need more help then update your question with a proper SSCCE demonstrating the problem. All questions should have a proper SSCCE, not just a few random lines of code so we can understand the context of the code.
I have:
A JFrame with a JButton on it.
A separate Canvas subclass to show animations.
And I wish to, at the press of the JButton bring up a new JFrame displaying the Canvas subclass as it animates.
The problem I face right now is that the new JFrame appears, however it doesn't get a chance to render anything and the JButton on the main frame stays depressed. The logic I figure behind this is that the EDT hasn't finished doing it's jobs such as showing the JButton as released and so does not get a chance to run the animation method and ends up in deadlock.
This logic treated me well in the past as I made this work by creating a new thread, but having learned more about Java, threads and Swing lately I've come to know that all Swing related events must be handled on one thread: the EDT.
This confuses me as to how I got it working before but lead me to believe that using invokeLater would help the problem; as the job of making the JFrame visible and showing animation would be placed at the end of the queue allowing the JButton to unrelease etc. I've had no luck however; have I completely misunderstood something?
Thanks!
(Also please no comments on my use of the Canvas class as opposed to JPanel, I have my reasons).
Sample code:
Test5 (class with main method).
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*
public class Test5 {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new Test5().setup();
}
});
}
private void setup() {
JFrame frame = new JFrame("Test");
JButton button = new JButton("Click here");
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
newFrame();
}
});
}
});
frame.getContentPane().add(button);
frame.pack();
frame.setVisible(true);
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
}
private void newFrame() {
JFrame newFrame = new JFrame("The new frame");
newFrame.setVisible(true);
newFrame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
CanvasClass canvas = new CanvasClass();
newFrame.getContentPane().add(canvas);
newFrame.pack();
canvas.runAnimation();
}
}
CanvasClass (Canvas subclass)
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
public class CanvasClass extends Canvas {
int x;
public CanvasClass() {
setSize(new Dimension(550,550));
this.x = (int) (Math.random() * 255);
}
//#Override
public void paint(Graphics g) {
g.setColor(new Color(x, x, x));
g.fillOval(0,0,500,500);
}
void runAnimation() {
while (true) {
randomise();
repaint();
try {
Thread.sleep(20);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
void randomise() {
x = (int) (Math.random() * 255);
}
}
You actualy invoke it in EDT but it's blocked in the canvas.runAnimation();
Place the code to be executed in a separate Thread (where you can call sleep) but call the repaint() in SwingUtilities.invokeLater()
Or even better to define a javax.swing.Timer and call the runAnimation() in the Timer's actionPerformed()
UPDATE:
int delay = 20; //milliseconds
ActionListener taskPerformer = new ActionListener() {
public void actionPerformed(ActionEvent evt) {
canvasInstance.randomise();
canvasInstance.repaint();
}
};
new Timer(delay, taskPerformer).start();
to be called instead of the runAnimation()
I am trying to make a thread that reads the screen and displays it in a frame, this code is meant to run at 5fps, so far it reads the screen, but I am having trouble making the JFrame display the updating Image each "frame" or 200 mili-seconds. when I use repaint(); or revalidate();
public static void startScreenRecorder()
{
Thread screenThread = new Thread()
{
public synchronized void run()
{
long time;
long lastFrameTime = 0;
JFrame frame = new JFrame("Screen capture");
ImagePanel panel = new ImagePanel(captureScreen());
frame.add(panel);
frame.setSize(300, 400);
frame.setVisible(true);
while (true)
{
time = System.currentTimeMillis();
while (time - lastFrameTime < 190)
{
try {
Thread.sleep(10);
} catch (Exception e) {
}
time = System.currentTimeMillis();
}
lastFrameTime = time;
panel = new ImagePanel(captureScreen());
panel.revalidate();
panel.repaint();
frame.revalidate();
frame.repaint();
}
}
};
screenThread.start();
}
Don't use Thread.sleep() to attempt to control animation.
Animation should be done by using a Swing Timer. When you use a Timer the GUI is automatically updated on the EDT.
panel = new ImagePanel(captureScreen());
The above code doesn't do anything. It just creates a panel in memory. Nowhere to you actually add the panel to the GUI. Changing the reference of a variable does not update the GUI.
Instead you should probably add a JLabel to the frame (when you initially create the frame). Then when you have a new Image you just do:
label.setIcon( new ImageIcon( your screen capture ) );
I wouldn't be surprised if your code shows no images at all since it ignores Swing threading rules:
All Swing code needs to be called on the Swing event dispatch thread (EDT) only.
All other long-running code needs to be called in a background thread. I assume that this means captureScreen().
You should never call Thread.sleep(...) on the Swing event thread unless you want to put your entire application to sleep.
Better perhaps to use a Swing Timer.
You create new ImagePanels but do nothing with them -- you never add them to the GUI for instance, except for the first JPanel. Note that if you change the object a variable refers to, here the panel variable, this will have absolutely no effect on instances of the object used elsewhere, there the JPanel displayed in the GUI.
Rather than create new JPanels, why not instead create ImageIcons with your images and swap a visualized JLabel's Icon with setIcon(...)?
Since you have a lot of background stuff going on, consider using a SwingWorker<Void, Icon> to do your work, and have it publish ImageIcons that are then displayed in the GUI's JLabel. If you did this, then you probably wouldn't use a Swing Timer since the timing would be done in the SwingWorker's background thread.
For example:
import java.awt.AWTException;
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.image.BufferedImage;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
#SuppressWarnings("serial")
public class SwingWorkerEg extends JPanel {
private static final int PREF_W = 600;
private static final int PREF_H = 400;
private JLabel displayedLabel = new JLabel();
public SwingWorkerEg() {
setLayout(new BorderLayout());
add(displayedLabel);
try {
MySwingWorker mySwingWorker = new MySwingWorker();
mySwingWorker.execute();
} catch (AWTException e) {
e.printStackTrace();
}
}
public void setLabelIcon(Icon icon) {
displayedLabel.setIcon(icon);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
private class MySwingWorker extends SwingWorker<Void, Icon> {
private final Rectangle SCREEN_RECT = new Rectangle(0, 0, PREF_W,
PREF_H);
private Robot robot = null;
public MySwingWorker() throws AWTException {
robot = new Robot();
}
#Override
protected Void doInBackground() throws Exception {
Timer utilTimer = new Timer();
TimerTask task = new TimerTask() {
#Override
public void run() {
BufferedImage capturedImage = captureScreen();
publish(new ImageIcon(capturedImage));
}
};
long delay = 200;
utilTimer.scheduleAtFixedRate(task, delay, delay);
return null;
}
#Override
protected void process(List<Icon> chunks) {
for (Icon icon : chunks) {
setLabelIcon(icon);
}
}
private BufferedImage captureScreen() {
BufferedImage img = robot.createScreenCapture(SCREEN_RECT);
return img;
}
}
private static void createAndShowGui() {
SwingWorkerEg mainPanel = new SwingWorkerEg();
JFrame frame = new JFrame("SwingWorker Eg");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
Which would display...
I have this project that I need to publish, but don't know which way will be best. Can somebody help me please.
I have a Gui application(Jframe). In there I have a Jpanel that contains some animations (implement runnable). So in my main method I would call the constructor first, so everything display nicely, then called Runner.start(). (Thread)
So basically the gui pop up and then the animation happens, to be specific the animation is just the title of my program that slides in.
Now I want to put this on the website so my students can use.
I do not want to use java web start, i want this to act as an applet.
So do i put this jframe into my applet?
or should I convert this whole thing from jframe to japplet? and is this applet need to implement Runnable?
The thing that bug me is that Japplet has no main method, so how can I specified when my Jpanel can execute its animation? I want the animation to occur after everything has load up on the screen, not before.
I guess put it as the last statement of init() method? Correct me if I am wrong.
Thanks,
I have a Gui application(Jframe). .. I want to put this on the website so my students can use.
While it is possible to convert the frame to an applet, a better option is to launch the frame from a link using Java Web Start.
you can do both:
MainGui
import java.awt.BorderLayout;
import javax.swing.*;
public class MainGui extends JPanel {
public MainGui() {
this(null);
}
public MainGui(MyJApplet applet) {
this.applet = applet;
if (!isApplet()) {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
} else
frame = null;
setLayout(new BorderLayout());
// setPreferredSize(new Dimension(640, 480));
SwingUtilities.invokeLater(new Runnable() {
public void run() {
MainGui.this.run();
}
});
}
String title() {
return "Title";
}
public void addContent() {
add(new JLabel("add content! top"));
}
void run() {
if (isApplet()) addContent();
else {
frame.setTitle(title());
frame.getContentPane().add(this, BorderLayout.CENTER);
addContent();
frame.pack();
System.out.println(getSize());
frame.setVisible(true);
}
}
boolean isApplet() {
return applet != null;
}
public static void main(String[] args) {
new MainGui(null);
}
protected final JFrame frame;
protected final MyJApplet applet;
private static final long serialVersionUID = 1;
}
MyJApplet
import java.awt.BorderLayout;
import javax.swing.JApplet;
public class MyJApplet extends JApplet {
public void start() {
}
public void init() {
getContentPane().setLayout(new BorderLayout());
addContent();
}
public void addContent() {
getContentPane().add(new MainGui(this), BorderLayout.CENTER);
}
public static void main(String[] args) {
new MainGui(null);
}
private static final long serialVersionUID = 1;
}