Java-KeyListener：在给定时间范围内捕获输入

Question

I'm currently working on a project using a barcode reader.

I have a GUI and a JTable on which I have applied a keyListener .

Basically, I want to scan a barcode and add the corresponding element from a database into the JTable .

When I scan a barcode (using e.getKeyChar() ) it sends the characters seperately however in a short time (milliseconds).

Hence I want to store the all of the characters for a given time (let's say 100 milliseconds) in a String so that it groups it into one item.

I could use that later to look up in the database for the item.

I do not know how long the barcodes are some of them are shorter and some longer.

I was thinking of using System.currentTimeMillis() and figure out a timer so that once there is an input a timer starts and stops after 100 milliseconds and then stores all of the characters typed within that time frame into an array or String.

How would I create such a method?

I appreciate any help I could get.

Answer 1

For your key listener, try using something similar to this

It's mostly for the logic of using a timer on the first press

new KeyListener()
{
    LinkedList<KeyEvent> list = new LinkedList<KeyEvent>(e);

    public void keyPressed(KeyEvent e)
    {
        if(list.peek() == null)
            startTimer();
        list.push(e);
    }

    public void keyReleased(KeyEvent e)
    {
        if(list.peek() == null)
            startTimer();
        list.push(e);
    }

    public void keyTyped(KeyEvent e)
    {
        if(list.peek() == null)
            startTimer();
        list.push(e);
    }

    private void startTimer()
    {
        new Thread()
        {
            public void run()
            {
                sleep(100);
                doStuff();
            }
        }.start();
    }

    private void doStuff()
    {
        //do stuff with the list using list.pop() - export to string and what not and end up with an empty list
    }
}

It should be mostly fine for concurrency issues, but to make sure you could use list as a synchronization lock

Also you could probably use a single thread if you use something similar, but instead of a Thread to check after 100ms, use a long timer to check the time against each time a key is pressed/typed/released and call doStuff before adding to the stack

new KeyListener()
{
    LinkedList<KeyEvent> list = new LinkedList<KeyEvent>(e);
    long startTime;

    public void keyPressed(KeyEvent e)
    {
        if(System.currentTimeMillis() - startTime > 100)
            doStuff();
        list.push(e);
    }

    public void keyReleased(KeyEvent e)
    {
        if(System.currentTimeMillis() - startTime > 100)
            doStuff();
        list.push(e);
    }

    public void keyTyped(KeyEvent e)
    {
        if(System.currentTimeMillis() - startTime > 100)
            doStuff();
        list.push(e);
    }

    private void doStuff()
    {
        //do stuff with the list using list.pop() - export to string and what not and end up with an empty list
        startTime = System.currentTimeMillis();
    }
}

Do note that with this setup, the last barcode scanned will not automatically be processed

The barcodes will the processed at the start of the next barcode, which means you'll need to throw in some dummy data at the end of the program to get the last barcode, or manually call doStuff() on the listener somehow