Bring task with activity stack to front knowing package name

I have the following scenario.

I run application A with known packagename that starts Activity A1 as the main activity from the launcher. Now from A1 I launch another activity of this application that possibly is a settings activity or something else, let's call it A2. So our stack is A1-A2.

Now I switch back to the homescreen by pressing home. I start another application, let's call it B. B now wants to be able to switch back to the c开发者_运维问答urrently paused A application preserving its activity stack. That would mean we have B-A1-A2 at the end. Is that possible in general? Please note that I only know the package name of A and do not have any more information about application A.

Here is what I already tried without success:

Intent intent = getPackageManager().getLaunchIntentForPackage(PKGNAME);
            if(intent!=null)
            {
                intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
                startActivity(intent);
                finish();
            }

But this gives B-A1-A2-A1.