How to manipulate current task's Activity back stack?

Question

Currently I have 3 Activity classes A, B and C.

Activity A is a singleTask while other has the default launch mode. Consider a case: the user is first in A, then starts B, and then starts C.

The back stack now is ABC.

Next, the user starts A again.

The back stack now is A, but what I would like to be achieved is ABCA.

I know not setting Activity A to be singleTask can have a back stack : ABCA. But I really need the Activity A to be the same instance.

Anyone know how to do this?

already look at the docs and see no way to archive this – Morty Choi May 27 '15 at 09:22 — Morty Choi, May 27 '15 at 09:22

Yash Sampat · Accepted Answer · 2015-05-27T09:21:29.203

2

You have stipulated two conditions:

what I would like to be achieved is ABCA.

and

I really need the Activity A to be the same instance.

These two conditions are mutually contradictory. Absolutely.

What you want is impossible.

That is all.

edited May 27 '15 at 09:21

answered May 27 '15 at 09:15

Yash Sampat

shobhan · Answer 2 · 2015-05-27T09:29:22.797

0

That is not possible.

if you want to open existing activity then

launch your activity as

    Intent intent = new Intent(this, YourActivity.class);
    intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
    startActivity(intent);

edited May 27 '15 at 09:29

answered May 27 '15 at 09:18

shobhan

that will lead to BCA, not ABCA – Yash Sampat May 27 '15 at 09:19
yes. As you (@Y.S.) told that his conditions are mutually contradictory. So that I gave this answer. – shobhan May 27 '15 at 09:24
ok, great, no problem :) ... i merely pointed out that this won't get the OP the result they want. – Yash Sampat May 27 '15 at 09:26
btw can we reorder a activity to back instead of front? – Morty Choi May 27 '15 at 09:33
No, Instead use same thing to another activity to which you want to order Front.. – shobhan May 27 '15 at 09:39

score 0 · Answer 3 · answered May 27 '15 at 09:22

0

Are you sure you need singleTask and not singleTop ? Could you describe why do you need it singleTask ?

answered May 27 '15 at 09:22

Ciprian

Because I want A to be a single instance. – Morty Choi May 27 '15 at 09:24
then maybe you should consider launching it with the same params and not make it singleTask, like @Y.S. said it's a bit contradictory what you want to achieve – Ciprian May 27 '15 at 09:26
Then consider the case of ABCA'BCA'', how can I jump back to A' or A immediately and clear the back stacks to ABCA' or A ? – Morty Choi May 27 '15 at 09:29
the answer for that would be CLEAR_TOP flag http://developer.android.com/reference/android/content/Intent.html#FLAG_ACTIVITY_CLEAR_TOP – Ciprian May 27 '15 at 09:32
CLEAR_TOP need to be used together with startActivity(indent), but how can you specific which A or A' is being start and CLEAR_TOP? – Morty Choi May 27 '15 at 09:34
well, how else would you "jump"? – Ciprian May 27 '15 at 09:35
just call finish() on Resume of each Activity until I reach the targeted Activity? Or its is okay to store a reference to each activities? So that I can explicitly call finish() on those activities I would like to close. – Morty Choi May 27 '15 at 09:39
I wouldn't do that. It will lead to unexpected behavior. This is the reason why the intent flags were introduced to play around with the activity/task stack. You can find more info here: http://developer.android.com/guide/components/tasks-and-back-stack.html – Ciprian May 27 '15 at 09:42

3 Answers3