如何同步两个swt按钮的事件？

Question

I have two SWT buttons, button("Start") & button("Stop"). When I press on "Start", I call a method: printFiles(inputPath, printer) //scans "inputPath" directory for pdfs and sends them to the printer "printer"

I want printFiles(inputPath, printer) to run always, untill I press the button("Stop"). So, that was my first thoughts how to do it.

//button("Start")
btnStart.addSelectionListener(new SelectionAdapter() {
@Override
public void widgetSelected(SelectionEvent arg0) {
    keepPrinting=true;
    while(keepPrinting){
        printFiles(inputPath, printer);
    }
}
});

//button("Stop")
btnStop.addSelectionListener(new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent arg0) {
            keepPrinting=false;
        }
});

But, there is an obvious problem. When I press on button("Start"), it never gets back from the while(true) loop. As a result, the whole window (shell) stops responding.

Do you have any idea how to put an endless loop inside button's press Listener?

My instict says I have to use concurrency, to synchronize these two buttons somehow. If that's correct, could you give some hints how to implemnt that?

Many thanks!

Answer 1

You shouldn't execute lengthy tasks on the GUI thread. Instead, start a new thread to do the work. In this simple case, you don't need complicated synchronization mechanisms, just replace

while(keepPrinting){
    printFiles(inputPath, printer);
}

with

new Thread() {
    @Override
    public void run() {
        while (keepPrinting) {
            printFiles(inputPath, printer);
        }
    }               
}.start();