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.
Related
In my program it opens a window if an action is happened. After I have filled out information in this window, and entered a button, the window dispose().
The window is picked up in a program outside my main program, but when I close this window, my main program stops. How can I prevent this from happening?
Thanks for your help!
You can set the defalaultCloseOperation property of the second frame to DO_NOTHING_ON_CLOSE or DISPOSE_ON_CLOSE
Don't even use two frames. Use a modal JDialog instead for a secondary frame. See more at How to Use Dialogs. Read more about Modality. And for a good read, see The Use of Multiple JFrames, Good/Bad Practice?
Forget about number 1. and go straight to 2.
If using JFrame or extending it you can use setDefaultCloseOperation() method like:
frame.setDefaultCloseOperation(HIDE_ON_CLOSE);
// or
frame.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
The dispose command is from the AWT Bundle, and this may cause problems, as you are attempting to "close" a swing window with an AWT command.
You can close the window with this command:
windowName.setVisable(false);
windowName is the name of the object representing the window. If you are extending a class, and have no object, you can use this
More Information on the Dispose Method:
"In general java.awt.Window.dispose() is used on a GUI component that is
a subclass of Window, in order for that specific GUI Window object (and
its children) to properly release and destroy native UI resources (such
as the screen). Garbage collection (and the eventual exiting of the
entire VM) may happen as a result of dispose(), but is not directly
connected with the dispose() call itself." From: https://www.java.net/node/684412
windowName.setVisable(false);
doesn't seems to be a good choice. What if user want to exit the program?
check this question - How to hide a JFrame in system tray of taskbar
Similar to this question I have the problem that the first JFrame I open takes way longer than ones afterward. I have an application that opens JFrames based on user input in the console. Because of this, I would have time to load the JFrame stuff in advance in a separate thread. What function of Swing or AWT should I call for this initialization to be executed (the other StackOverflow answer refers to some sun package which is no longer in the JRE/JDK)?
Swing: Just call everything you normally need to setup the GUI but don't invoke setVisible(true) on the JFrame until you want to display it. Note that the GUI should be created on the EDT, i.e. using SwingUtilities.invokeLater.
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.
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
In my program it opens a window if an action is happened. After I have filled out information in this window, and entered a button, the window dispose().
The window is picked up in a program outside my main program, but when I close this window, my main program stops. How can I prevent this from happening?
Thanks for your help!
You can set the defalaultCloseOperation property of the second frame to DO_NOTHING_ON_CLOSE or DISPOSE_ON_CLOSE
Don't even use two frames. Use a modal JDialog instead for a secondary frame. See more at How to Use Dialogs. Read more about Modality. And for a good read, see The Use of Multiple JFrames, Good/Bad Practice?
Forget about number 1. and go straight to 2.
If using JFrame or extending it you can use setDefaultCloseOperation() method like:
frame.setDefaultCloseOperation(HIDE_ON_CLOSE);
// or
frame.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
The dispose command is from the AWT Bundle, and this may cause problems, as you are attempting to "close" a swing window with an AWT command.
You can close the window with this command:
windowName.setVisable(false);
windowName is the name of the object representing the window. If you are extending a class, and have no object, you can use this
More Information on the Dispose Method:
"In general java.awt.Window.dispose() is used on a GUI component that is
a subclass of Window, in order for that specific GUI Window object (and
its children) to properly release and destroy native UI resources (such
as the screen). Garbage collection (and the eventual exiting of the
entire VM) may happen as a result of dispose(), but is not directly
connected with the dispose() call itself." From: https://www.java.net/node/684412
windowName.setVisable(false);
doesn't seems to be a good choice. What if user want to exit the program?
check this question - How to hide a JFrame in system tray of taskbar