Re: New Swing Window Not Drawn
Daniel Pitts wrote:
Hal Vaughan wrote:
I've created a small class that's not too different from a JOptionPane.
The purpose is to use it when I need to put up a "Please Wait" type
message or
something similar. I'm using a separate thread to show and hide the
window. The other actions that need to happen while this window appears
and later disappears are happening, but the window is not actually
rendered.
I know I need to use a separate thread when I have actions going on while
new Swing components are rendered or changed, and I'm doing that, but
that doesn't seem to make a difference.
Here's the method that is supposed to show the window and check
periodically to see if the window should be closed:
public void activate() {
//flagActive is set to false when the window should disappear
flagActive = true;
new Thread(new Runnable() {
public void run() {
System.out.println("-----Opening Wait Window.");
//jSelf is the JFrame class for the window
jSelf.setVisible(true);
while (true) {
try {Thread.sleep(50);} catch (Exception
e) {
System.out.println("Insomnia");
}
if (!flagActive) break;
}
System.out.println("-----Closing Wait Window.");
jSelf.setVisible(false);
}
}).start();
return;
}
I've had cases where I've used different threads like this before, but it
was always the new or internal thread that did the actions and the Swing
events were done by the "regular" thread.
Why is the window not being rendered here, even though it has its own
thread and Swing should be able to have time to render it?
Thanks!
Hal
All interaction with Swing components should be done on the Event
Dispatch Thread.
Look at the class SwingUtilities
<http://java.sun.com/j2se/1.5.0/docs/api/javax/swing/SwingUtilities.html>.
specifically the invokeLater() method
Instead of setting aFlag, you should simple fire an event on the EDT.
Even if you wanted to wait for the flag to change, you need to use
synchronization. You also shouldn't be using a busy wait (even if you
sleep for 50), but instead do something like this:
public void sleepWhileActive() {
synchronize(myLock) {
while (active) {
try {
myLock.wait()
} catch (InterruptedException e);
System.out.println("Insomnia");
}
}
}
}
public void setActive(boolean active) {
synchronize(myLock) {
this.active = active;
myLock.notifyAll();
}
}
But, like I said, you should be using the EDT instead...
public void activate() {
assert !SwingUtilities.isEventDispatchThread() : "This would cause
a deadlock"
SwingUtilities.invokeLater(new Runnable() {
System.out.println("-----Opening Wait Window.");
//jSelf is the JFrame class for the window
jSelf.setVisible(true);
});
doExpensiveOperation();
SwingUtilities.invokeLater(new Runnable() {
System.out.println("-----Closing Wait Window.");
jSelf.setVisible(false);
});
}
Thanks -- good examples and code and points to ponder.
It would seem to me I might be able to make it a bit simpler. This class is
supposed to be a simple "Please Wait..." window that I can customize and
flash up during longer operations. I might do it with a JOptionPane, but I
also need to understand this situation anyway. I've tried using
invokeLater before and had some problems getting it to work.
Instead of having any "aFlag" or "active" or any other variable, can't I do
something like this:
public void activate() {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
System.out.println("-----Opening Wait Window.");
jSelf.setVisible(true);
}
});
return;
}
public void deactivate() {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
System.out.println("-----Closing Wait Window.");
jSelf.setVisible(false);
}
});
return;
}
That would provide simple methods to both open and close the window.
The CPU cycle using activities are in another class. I was trying to make
this class a simple one that I could set up in a couple lines and call
without having to create separate threads or anything like that -- in other
words, the class itself would create any needed Runnable or Threads.
The calling code would look like this (assuming this class name is
WaitDialog):
WaitDialog wd = new WaitDialog();
//Follow with settings for wd here
wd.activate();
bigClass.doExtensiveThings();
wd.deactivate();
It seems to me that would still do everything the same way as what you're
talking about in the same way, just that the extra typing of creating a
Runnable() is in the WaitDialog class so all I have to do is call it with
two calls instead of creating a Runnable each time I use it.
Is that reasoning correct? If it is, I'm still having trouble getting it to
work, but I'd like to know if I understand this correctly first.
Hal