CODEWITHSUNDEEP
javamultithreading
Brett
Brett

Reputation: 386

Pause a thread to give user option to continue

I have a thread that copies a file and give the progress bar the progress, I have a method the stops the filestream copy and kills the thread, I am trying to implement a jOptionPanel yes_no to ask the user if they are sure they want to delete. But i need to be able to pause the fileInputStream copy until the thread either stops or is continued. The thread waits but the file copy keeps going. how can i fix this? Any help would be great

First is the thread I want to pause

thr = new Thread("cool") {
            @Override
            public void run() {
                while (running == true) {
                    try {
                        newWorkFileName();
                        long length = fileIn.length();
                        long counter = 1;
                        int r;
                        byte[] b = new byte[1024];
                        fin = new FileInputStream(fileIn);
                        fout = new FileOutputStream(fileOut);
                        tvConvertInterface.updateJLabel2("Creating File");
                        while ((r = fin.read(b)) != -1) {
                            counter += r;
                            fout.write(b, 0, r);
                            prog = (int) Math.round(100 * counter / length);
                            tvConvertInterface.updateJProgressbar1(prog);

                        }
                        fin.close();
                        fout.close();
                        tvConvertInterface.disableStopBtn();
                        tvConvertInterface.updateJLabel2("Work File Created");
                        running = false;
                    } catch (NullPointerException | IOException ex) {
                        tvConvertInterface.disableStopBtn();
                        tvConvertInterface.updateJLabel2("File is not valid");
                        Logger.getLogger(TvConvertGutts.class.getName()).log(Level.SEVERE, null, ex);
                        tvConvertInterface.updateJProgressbar1(0);
                        running = false;
                    }
                }
            }
        };

Next is the Method that i want to implement the jOptionPanel

public boolean terminate() throws IOException, InterruptedException {
        synchronized (thr) {
            thr.wait();//MAKES THREAD WAIT

            //I NEED TO PAUSE THE FILESTREAM AND BE ABLE TO RESUME
        }
        int n = JOptionPane.showConfirmDialog(
                null, "SURE YOU WANT TO DELETE?",
                "Kill It Dude",
                JOptionPane.YES_NO_OPTION);
        if (n == JOptionPane.YES_OPTION) {
            fin.close(); //CLOSE INPUT STREAM
            fout.flush();//FLUSH OUTPUT STREAM
            fout.close(); //CLOSE OUTPUT STREAM
            thr.interrupt();//KIILL THE THREAD
            System.out.println(thr.getState());//PRINT STATE OF THREAD
            TvConvertInterface bst = new TvConvertInterface(null, true);
            bst.disableStopBtn();//SET PROGRESSBAR TO 0
        } else if (n == JOptionPane.NO_OPTION) {
            synchronized (thr) {
                thr.notify();//DONT DELETE AND CONTINUE
            }
        } else {
            System.out.println("spewin");
        }

        return false;
    }

This terminate method is called by a button click. From a class called TvConvertInterface

private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        try {

            check.terminate();
        } catch (IOException ex) {

            Logger.getLogger(TvConvertInterface.class.getName()).log(Level.SEVERE, null, ex);
        }

Upvotes: 0

Views: 61

Answers (1)

Crazyjavahacking
Crazyjavahacking

Reputation: 9687

You are using the JAVA concurrency API incorrectly.

The object.wait() will pause the current thread and the object in this case would serve as a monitor object.

What you need to do is the following:

  1. define a boolean shouldPauseThread variable
  2. the while loop should check for the value in this variable; if it is true you should wait on a monitor object
  3. if the user approves the cancelling, then the thread should end its execution, so there needs to be a check for another variable boolean stopThread
  4. if the user wants to continue with processing, you will just reset the shouldPauseThread variable and notify on the previously used monitor object
  5. you need to handle all the transitions from the mentioned states

Upvotes: 1

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