I have a program that I am terminating with the System.exit(0); command.
When this happens the JPanel closes. I would like it to rename open so I can view the state at termination. Is there a way of keeping the Jpanel open or is there a better command than System.exit()?
not sure why a down vote I asked a simple question and someone answered it. I can't do it that way so try something else. Going to use a true false to test where to enter the simulation loop.
regarding:
Is there a way of keeping the Jpanel open or is there a better command than System.exit()?
The best solution: Don't call System.exit(...). Why? Because System.exit(0) closes the JVM, and so all Java processes running on that JVM will shut down when System.exit(0) is called.
As for "better command", that all depends on your need. If you just want to close a window such as a JDialog, then call myWindow.setVisible(false);. If you want to close it and release resources, then myWindow.dispose();.
Note: I suspect that you might have multiple windows open, perhaps multiple JFrames. If so, I strongly urge you to read: The Use of Multiple JFrames, Good/Bad Practice?
You also posted in comments:
I would like to keep the Jpanel open, but stop the simulation from running. I need to stop the Sim when certain conditions are met. so I wrote a stop()
So your question is in fact an XY Problem where you ask how to solve a specific code problem (keep a JPanel open after calling System.exit(0)) when the best solution is to use a completely different approach. Better that you tell us the overall problem that you're trying to solve rather than how you're currently trying to solve it, because System.exit isn't going to be part of the best solution.
Likely the best solution is to well separate your simulation model from its view (the GUI), to be able to give the model functionality that allows it to stop without closing down the JVM -- impossible for me to say how given our current level of knowledge about your problem -- and then reflect the stopping of the model in the view, again without shutting down the system.
The key to all of this will lie in the details of your current program, including the logic that underpins your simulation, and if you need more specific and likely more helpful answers, you're again going to want to improve your question, providing us with much more specific information about your code, your problem and with posting of pertinent code, preferably as a minimal example program.
Have you tried an approach similar to:
Do something when the close button is clicked on a JFrame
Basically, you're grabbing the Window closing event by setting a listener on the frame
You can then .dispose() the appropriate jpanel/frame if you want
JFrame is window and JPanel is a container. The moment the JPanel instance loses its reference, it will be garbage collected
How can JPanel be disposed after the panel has been removed from the JFrame
Disposing JFrame by clicking from an inner JPanel
import javax.swing.JOptionPane;
/*Some piece of code*/
frame.addWindowListener(new java.awt.event.WindowAdapter() {
#Override
public void windowClosing(java.awt.event.WindowEvent windowEvent) {
//delete this code if you want and replace with .dispose() or anything
if (JOptionPane.showConfirmDialog(frame,
"Are you sure to close this window?", "Really Closing?",
JOptionPane.YES_NO_OPTION,
JOptionPane.QUESTION_MESSAGE) == JOptionPane.YES_OPTION){
//choose to close JVM here if you want
System.exit(0);
}
}
});
Here's a way, by overriding the SecurityManager for the JVM:
//set your security manager
static{
SecurityManager s = new DontCloseOnExitSecurityManager();
System.setSecurityManager(s);
}
static class DontCloseOnExitSecurityManager extends SecurityManager{
public void checkExit(int code){
//here you can put a check to see if you really do want to close - like if the JFrame is still open.
if(/*do some check*/ 13 == code)
super.checkExit(code);
throw new SecurityException("13 is unlucky, you shouldn't system exit on it.");
}
}
}
You'll need to find an appropriate place to put it in, and also how to do your checks (in checkExit).
Apologies for inaccuracies, I'm not in front of an IDE to test this right now.
Related
I want to close/terminate/throw away a JPanel that was created by a line of code (so it's completely terminated, not just hidden and running in the background as setVisible(False); does) and without closing the whole program as System.exit(0); does.
How can I do that ?
I want to close/terminate/throw away a JPanel that was created by a line of code (so it's completely terminated, not just hidden and running in the background as setVisible(False); does) and without closing the whole program as System.exit(0); does.
There's nothing wrong with simply calling setVisible(false) on the JPanel, or better, swapping it for another via CardLayout.
It appears that you're looking for some micro-optimization, but you're not going to get much by chasing this. Make it non-visible and move on..... unless of course there are more details about your code and your problem that we're currently not aware of, and if so, then please let us know.
I have a fairly simple Java Application I created with JFrames. There is more than one JFrame in my program. I have a menu launching at the beginning of the program. After going through the menu, I have the menu JFrame disposed.
The main JFrame has a menu button that should launch the exact same menu at a later time. However, when you launch the menu from inside of the ActionListener (when you press the menu button), the JFrame doesn't launch properly. None of the components show up and colors are off.
However, when the menu is launched from outside of the ActionListener, the JFrame shows up perfectly. I have tried multiple methods to fix this, but none of them have worked.
My full program code is available by clicking here.
The main class is "LetsMultiply5.java". This class also sets up the ActionListener.
The JFrame causing the problem is "MenuWindow.java".
"LetsMultiply5.java" calls the "Booter.java" class, which then calls the "MenuWindow.java".
"MainWindow.java" is the JFrame that has the "Menu" button.
For proof, "SpeedModer.java" calls the menu window after it has been disposed, and works.
================================EDIT================================
Also, I'd like to let you know that I realize my code is a little bit messy. I am not sure how else to write the code for this program.
I am forced to use Thread.sleep(x); because the Swing timers aren't what I am looking for. The Swing timers activate an ActionListener when the timer goes off. I need a system that will wait a second before continuing on with the code.
I realize that the while (repeater==0) loop with ActionListeners inside of it seems crazy, but that was the only way I could get it to work. If I put a single ActionListener and just had the while loop do no code inside of it, nothing happens when I press the button.
I would, as MadProgrammer mentioned:
Advice: Scrap your current approach and start again.
However, the way that I have my program currently coded is the only way that I know how to get what I need to do done. I read the tutorials, but still don't know how to improve the code in the way that you told me.
I thank everyone for trying to tell me to improve my bad "Java grammar", but as far as I am concerned, I am not going to continue this program for the next 20 years and make my millions off of it.
I have looked at the Swing timers before and I understand the whole new Timer(speed, this); concept, but I don't understand how this would make my code any better.
If anyone would like to show me how to fix my ActionListeners or Thread.sleep(x); lines, please tell me. Thank you.
You're blocking the Event Dispatching Thread with Thread.sleep(3000); - Don't do this, it will prevent the UI from been painted
See Concurrency in Swing for more details about the problem and How to use Swing Timers for a possible solution
You may also want to consider having a look at The Use of Multiple JFrames, Good/Bad Practice? and consider using CardLayout or JTabbedPane
If you need to block the user temporarily (to display a error message or gather important details), consider using a modal JDialog. See How to Make Dialogs for more details
I have a simple Swing application which runs in full screen mode. My application instantiates a JFrame, which in turn instantiates a JPanel, where all of the drawing is done in the paintComponent method. I also have a MouseListener watching for certain events.
One of those events (clicking on a certain area of the screen) triggers a prompt. Here is my code to show the prompt (keep in mind this comes from within my class that is extending JPanel).
int choice = JOptionPane.showConfirmDialog(this, "Are you sure you want to quit?", "Quit?", JOptionPane.YES_NO_OPTION);
if ( choice == JOptionPane.OK_OPTION ) {
dialogOpen = false;
System.exit(0);
} else {
dialogOpen = false;
repaint();
}
The only trouble is... as soon as this code runs, the entire window disappears. More specifically, it looks like it minimizes itself, because I can click on the Java icon in the taskbar and it pops right back up. But how do I stop it from minimizing itself? All I want to do is display a simple prompt!
I figured it out. Thanks to everyone for their helpful comments (what is it with people and commenting here, by the way? how come people write everything that could go in an answer in the comments instead?)
Rather than calling .showConfirmDialog(this, ...) (where this is my JPanel subclass), I needed to call .showConfirmDialog(parent, ...) (where parent is my JFrame subclass). Then, I added a WindowStateListener on the JFrame to detect state changes and reset the window state.
Ok so I'm not sure why my MouseListener isn't working but I think it might be because I implemented both the ActionListener and MouseListener into the class. Would this cause the class to have an issue?
actionPerformed method:
public void actionPerformed(ActionEvent e){...
...
}
mouseClicked method:
public void mouseClicked(MouseEvent arg0) {
...
}
Is it because it's only listening to the actionPerformed method and never entering the MouseListener? If what I suspect is correct, how would I allow it to work together?
EDIT: I've narrowed it down to something is wrong in the MouseListener. It doesn't ever get any input from the mouse at all, do I have to specify the area it should be listening to?
public void mousePressed(MouseEvent arg0) {
System.out.println("Inside timer is running");
if(timer.isRunning() == true){
System.out.println("Inside timer is running");
Point p = arg0.getPoint();
}
}
You ask:
Ok so I'm not sure why my MouseListener isn't working but I think it might be because I implemented both the ActionListener and MouseListener into the class. Would this cause the class to have an issue?
No, this should not affect things at all. Your problem most likely lies elsewhere in code not shown.
Having said this, I'd like to add that almost none of my GUI classes implement either of these or other listener interfaces, since I feel that this would be asking the class to have too much responsibility, making it harder to debug now or upgrade later. Instead I favor either anonymous inner classes that then call control methods, or a completely separate control/listener class(es).
Edit
I don't think that your posted code and text is adequate to allow us to understand your problem enough to answer it other than to say that the problem lies elsewhere. If you don't get a decent answer soon, consider creating and posting a Minimal, Complete, and Verifiable Example Program.
Edit 2
You state in comment:
I don't think I could post anymore code that may clear it up since this is a huge program. This class alone has 300 lines but I know everything else works just the MouseListener isn't working like it should
Up to you what you should do next, but if this were my code, and I were running into these problems, I would work some more on trying to isolate the problem, including refactoring my code so that that I eventually come up with the smallest critical code that reproduces the problem. You're probably coming here at too premature of a stage in your debugging, forcing you to post "what if" scenarios, and for us to shrug our shoulders and say, "who knows".
Edit 3
You ask:
do I have to specify the area it should be listening to?
You have to specify what component to listen to. MouseListeners listen to components. But again, this is little more than more "what if's" and "who knows"...
I have one JFrame. That JFrame has a window listener for closing events which are intercepted and provide the user with options prior to closing the entire program.
Must I call dipose() on a JFrame or am I safe to call only System.exit(0)? Secondly, should I only call dipose() on a JFrame or should I call dipose() followed by System.exit(0)?
My question is must I call dipose() on my JFrame object or can I safely call System.ext(0)?
Why would you ask this? You should solve you compile problem first, and then decide what approach you want to use. Don't use System.exit() just because you don't know how to get rid of a compile error
am using a WindowAdapter as
There is no need for you to keep a variable in order to reference your frame. The best approach to access the frame is to get the frame from the WindowEvent:
JFrame frame = (JFrame)event.getSource();
To answer your original question I would use dispose(). It will eventually invoke System.exit() if it is the last frame open in your application.
Edit:
I want to give the user an option to do something productive before closing the program down
You can check out Closing an Appliction for more ideas on this topic.