Question

How to make an eclipse plugin open a new-generated document in the main view (something like a hello.txt file) when the user switches to its perspective?

Answer 1

Something like this would be typical code for this task:

String fileContents = ...;
IFile file = ...;
file.create(new ByteArrayInputStream(fileContents.getBytes()), true, null);
FileEditorInput input = new FileEditorInput(file);
PlatformUI.getWorkbench().getActiveWorkbenchWindow().
    getActivePage().openEditor(input, THE_EDITOR_ID);