Usually it makes sense to use it if you have a task that may run in the background. If you need to block the whole IDE I guess you need to do it in a modal dialog-way.
But most of the long tasks may safely run in the background. With Progress API you just declare your new task and then in the lower-right part of the main window you'll see a progress bar.
Usually you have two kinds of tasks: tasks execute a predetermined number of steps and you could estimate something like a percentage realised so far and tasks that could go on for ever.
The fun part about the Progress API is not only that it allows you to have *determinate* and *indeterminate* kind of progress handles (this is how your little presenter is called) but it also allows you to switch between determinate and indeterminate tasks.
Imagine this: you take a locally-saved HTML file and need to re-save it with links up to a depth. For all local links you pretty much know it's going to take little time to copy the file so you have a determined progress (with a percentage shown) but once you start downloading something from the net you have no ideea how much it will take. So you switch to indeterminate and the user sees just an indefinite progress bar.
Even better, you could have more than one task running at one point. So if you click on the progress bar for the current task, a popup will appear with all the tasks.
Now, if you need this for standalone non-Platform based apps, you might find https://progress-api.dev.java.net/ usefull. There is one app where I used it and it works great !On holiday during the 24 august - 31 september period.
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