progressbar in a thread does not update its UI until the work was done in the main thread

Question

i am cutting a big file into blocks, and want to display the rate of the progress. when i click startCut Button, here is the code to execute：

FileInputStream         


        

Answer 1

You've got two problems here:

• You're doing long-running work in the Swing dispatcher thread, which means you're stopping it from processing events. (Try moving windows around etc - it will fail.)
• You're updating the UI from the wrong thread at point A. It sounds like you're getting away with this at the moment, but it's still a bug.

You should use SwingWorker or SwingUtilities to address both of these issues. Basically, you mustn't access the UI from a non-UI thread, and you mustn't do long-running work on a UI thread. See the Swing concurrency tutorial for more information.