Question

In intent I can set such flag as FLAG_ACTIVITY_SINGLE_TOP. Can somebody explain me its meaning, cause I just don’t get it? =)

Answer 1

The tasks page says for single top:

If an instance of the activity already exists at the top of the current task, the system routes the intent to that instance through a call to its onNewIntent() method, rather than creating a new instance of the activity. The activity can be instantiated multiple times, each instance can belong to different tasks, and one task can have multiple instances (but only if the the activity at the top of the back stack is not an existing instance of the activity).

For example, suppose a task’s back
stack consists of root activity A with
activities B, C, and D on top (the
stack is A-B-C-D; D is on top). An
intent arrives for an activity of type
D. If D has the default “standard”
launch mode, a new instance of the
class is launched and the stack
becomes A-B-C-D-D. However, if D’s
launch mode is “singleTop”, the
existing instance of D is deliverd the
intent through onNewIntent(), because
it’s at the top of the stack—the stack
remains A-B-C-D. However, if an intent
arrives for an activity of type B,
then a new instance of B is added to
the stack, even if its launch mode is
“singleTop”.