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Access Swing Component infinitely from a separate thread (without "freezing" the app)

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Join Date: Feb 2006

Posts: 2,467

Reputation: masijade has much to be proud of

Solved Threads: 267

masijade

Offline

Nearly a Posting Maven

#11

Oct 16th, 2009

Change this

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Originally Posted by Clawsy

Help with Code Tags

Java Syntax (Toggle Plain Text)
    usbThread thread = new usbThread();
 
    public detectUSB() {
        initComponents();
 
        thread.start();
 
 
        final JLabel label = lbl_status;
        final String text = thread.getThreadStatus();
 
        SwingUtilities.invokeLater(
                new Runnable() {
                    public void run() {
                        label.setText(text);
                        label.validate();
                        label.repaint();
                    }
                }
            );
    }
usbThread thread = new usbThread(); public detectUSB() { initComponents(); thread.start(); final JLabel label = lbl_status; final String text = thread.getThreadStatus(); SwingUtilities.invokeLater( new Runnable() { public void run() { label.setText(text); label.validate(); label.repaint(); } } ); }

to this

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
    public detectUSB() {
        initComponents();
    }
    public detectUSB() {
        initComponents();
    }

and change this

•

Help with Code Tags

Java Syntax (Toggle Plain Text)
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new detectUSB().setVisible(true);
            }
        });
    }
public static void main(String args[]) { java.awt.EventQueue.invokeLater(new Runnable() { public void run() { new detectUSB().setVisible(true); } }); }

to this

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new detectUSB().setVisible(true);
            }
        });
        new usbThread(lbl_status).start();
    }
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new detectUSB().setVisible(true);
            }
        });
        new usbThread(lbl_status).start();
    }

and change this

•

Help with Code Tags

Java Syntax (Toggle Plain Text)
public class usbThread extends Thread{
    public String status=".....";
    usbThread()
    {
 
    }
 
    String getThreadStatus()
    { 
      return this.status;
    }
 
    @Override
    public void run() {
        ....
        this.status="FindDrive: waiting for devices...";
            ....
                this.status="Drive "+letters[i]+" has been plugged in";
            else
                this.status="Drive "+letters[i]+" has been unplugged";
                ....
            }
            try { Thread.sleep(100); }
            catch (InterruptedException e) { /* do nothing */ }
        }
    }
public class usbThread extends Thread{ public String status="....."; usbThread() { } String getThreadStatus() { return this.status; } @Override public void run() { .... this.status="FindDrive: waiting for devices..."; .... this.status="Drive "+letters[i]+" has been plugged in"; else this.status="Drive "+letters[i]+" has been unplugged"; .... } try { Thread.sleep(100); } catch (InterruptedException e) { /* do nothing */ } } }

to this

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
public class usbThread extends Thread{
    private String status = ".....";
    private JLabel label;
    usbThread(JLabel label) {
        this.label = label;
    }
 
    private void postStatus() {
        SwingUtilities.invokeLater(
                new Runnable() {
                    public void run() {
                        label.setText(status);
                        label.validate();
                        label.repaint();
                    }
                }
            );
    }
 
    @Override
    public void run() {
        ....
        this.status="FindDrive: waiting for devices...";
        postStatus();
            ....
                this.status="Drive "+letters[i]+" has been plugged in";
            else
                this.status="Drive "+letters[i]+" has been unplugged";
                ....
            }
            postStatus();
            try { Thread.sleep(100); }
            catch (InterruptedException e) { /* do nothing */ }
        }
    }
public class usbThread extends Thread{
    private String status = ".....";
    private JLabel label;
    usbThread(JLabel label) {
        this.label = label;
    }

    private void postStatus() {
        SwingUtilities.invokeLater(
                new Runnable() {
                    public void run() {
                        label.setText(status);
                        label.validate();
                        label.repaint();
                    }
                }
            );
    }

    @Override
    public void run() {
        ....
        this.status="FindDrive: waiting for devices...";
        postStatus();
            ....
                this.status="Drive "+letters[i]+" has been plugged in";
            else
                this.status="Drive "+letters[i]+" has been unplugged";
                ....
            }
            postStatus();
            try { Thread.sleep(100); }
            catch (InterruptedException e) { /* do nothing */ }
        }
    }

Last edited by masijade; Oct 16th, 2009 at 7:13 am.

Java Programmer and Sun Systems Administrator

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--Brian Kernighan

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Join Date: Oct 2009

Posts: 28

Reputation: moutanna is an unknown quantity at this point

Solved Threads: 6

moutanna

Offline

Light Poster

#12

Oct 16th, 2009

Thefact is the plaggedIn variable and isDrivev[i] are always equal so you the code inside the for bloc is never executed:
if you try this:
if(drives[i].canRead()) {
this.status.............
}else{
this.status.......
}

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Join Date: Feb 2008

Posts: 104

Reputation: Clawsy is an unknown quantity at this point

Solved Threads: 5

Clawsy

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Junior Poster

#13

Oct 16th, 2009

THANK YOU SO MUCH FOR SOLVING MY PROBLEM. I guess not only me was searching for this.

One note for the master

: when said to add "new usbThread(lbl_status).start();" to the main function. You cannot cause main is static (you get build error). So I just started it after " initComponents();".

THANK YOU SO MUCH!

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Join Date: Feb 2006

Posts: 2,467

Reputation: masijade has much to be proud of

Solved Threads: 267

masijade

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Nearly a Posting Maven

#14

Oct 16th, 2009

Sorry, brainfart.

Starting after initComponents (if done within the SwingUtilities) is bad as you are kicking it off from the Swing Event Thread, and you should, really, avoid that, if possible. Try it this way. Remove the "detectUSB" constructor and then change the main as follows:

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
    public static void main(String args[]) {
        detectUSB dusb = new detectUSB();
        SwingUtilities.invokeLater(new Runnable() {
                public void run() {
                    dusb.initComponents().setVisible(true);
                }
            });
        new usbThread(dusb.lbl_status).start();
    }
    public static void main(String args[]) {
        detectUSB dusb = new detectUSB();
        SwingUtilities.invokeLater(new Runnable() {
                public void run() {
                    dusb.initComponents().setVisible(true);
                }
            });
        new usbThread(dusb.lbl_status).start();
    }

And, in any case, change the usbThread constructor as follows:

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
    usbThread(JLabel label) {
        this.label = label;
        setDaemon(true);
    }
    usbThread(JLabel label) {
        this.label = label;
        setDaemon(true);
    }

To ensure that the thread dies properly.

Edit: And, not intending to nitpick, it is standard Java programming convention to capitalise Classes so those class names should be DetectUSB and USBThread.

Last edited by masijade; Oct 16th, 2009 at 9:55 am.

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Join Date: Feb 2008

Posts: 104

Reputation: Clawsy is an unknown quantity at this point

Solved Threads: 5

Clawsy

Offline

Junior Poster

#15

Oct 16th, 2009

Yes. Thank you

. These are really good hints and valuable advices. (but I put " new usbThread(lbl_status).start();" in formWindowOpened event cause... again: Builder said 'non-static variable lbl_status cannot be referenced from a static context'... sorry

). Thanks. Now I even optimized my application.

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