It sounds like there are two questions here:
- Why are only some files in my context showing when I select "Focus on Active Task"?
- How can I view files not in my context when I've selected "Focus on Active Task"?
For item one, Mylyn records every file you touch when working on a task and stores it as part of the task context (see note at end). For large tasks it quickly becomes useless to see every file that you've touched and so Mylyn uses an algorithm to decide which files are most relevant to your task, based on how many times you've viewed and edited them. Thus, when you select "Focus on Active Task" only the most relevant files are shown.
For item two, it is often the case that you'd want to view files that are not shown as part of your context while "Focus on Active Task" is selected, and Mylyn provides a way of doing this. You can view all children files of a visible node by holding down ALT while clicking on that node. The files will become visible temporarily. Similarly, if you do not have any files showing in context you can hold ALT and click in the Package Explorer (or other view of the project) and it will show all files. ALT + clicking is an essential action for anyone who wants to work with their PackageExplorer focused.
The 2.5 minute video Get Task-Focused will help you better understand how focusing the Package Explorer is intended to be used.
David Shepherd
Tasktop Technologies, Inc.
Note: You can see every file that is in your context by opening the task editor, selecting the "Context" tab (at the bottom), and then sliding the "Actions" slider to the left.