Question

I have a java swing application which has a form that I populate by scanning a barcode containing tab (or $I) delimited data as keyboard input through a USB connection. Intermittently, the form’s text fields are incorrectly populated such that it appears the tab is processed too late. For example, if the data set in the barcode is something like ‘abc$Idef’, the expected output would be ‘abc’ in the 1st text field and ‘def’ in the 2nd text field. What we see sometimes instead is ‘abcde’ in the 1st text field and ‘f’ in the 2nd or even all data in the 1st text field and nothing in the 2nd.

I have seen this issue manifest at different frequencies across different days. Today could be good and I only see it happen 1 out of every 150 attempts. Yesterday it could have been poor, happening 1 out of 10 attempts. The scanner is at or near default factory settings with the exception of me toggling the parameter to implement tab vs $I delimiter. I have also attempted slowing down the transmission speed, and while that does appear to decrease the frequency of events, it does not eliminate them and the the slowed speed is not ideal for user workflow and so, reset it to full speed.

I am doubtful that the issue lies within the scanner however. in the application, I’ve attempted to disable all text field validations and data backups to essentially remove any custom code which might cause some delay, but the intermittent issue still exists. Currently the application is running on a WinXPSP3 using JRE 1.5.0_18. The scanner is a Symbol model ds6707. I could use some guidance in investigating this issue further to determine where the problem may lie.

Answer 1

Consider reading the stream on a separate thread and posting completed units on the EventQueue. This will ensure that events arrive “Sequentially…In the same order as they are enqueued.” SwingWorker is convenient for this, as the process() method executes “asynchronously on the Event Dispatch Thread.”