Android back stack

Question

I have an application with several Activities in Android A,B,C,D. I have a question about the back stack.

A->B->C->D it is a normal sequence.

My question is : when i press the back button in Activity D, i have to go to the Activity B, not back to ActivityC. Since ActivityC have some imageView i want to save, i don't want to use noHistory to destroy the ActivityC. it is possible to do that

A1->B1->C1->D1

the back stack should be: D1->B1->A1 . C1 saved some imageView and if C1 launch again, the imageView in C1 will contain the same images. Is it possible just modify the code in ActivityC??

thank you

Don't add C to backstack ,so that while pressing back it will directly go to B. — Sunil Sunny, Mar 22 '17 at 06:42
handle the transition in onBackPressed() of each activity and navigate Accordingly — Quick learner, Mar 22 '17 at 06:48
At what point of time, you want to save the image in activity C? — Yash, Mar 22 '17 at 06:50
@sunil sunny But if don't add C to backstack, activityC will be destroyed and the data will be gone — yeun hang yeung, Mar 22 '17 at 06:51
@uick learner Have other method to do that?? Because i cannot modify the code in ActivtiyB and ActivityD, i just modify the code in ActivityC — yeun hang yeung, Mar 22 '17 at 06:52
@yeunhangyeung No you are not destroying C.It's still there, you didn't add it to stack that's all. What you want to do is create a main class and all the fragments will be navigated from here. So you have instances of all the fragments and you can use instance of C to see the saved image. — Sunil Sunny, Mar 22 '17 at 07:17
@sunil sunny how to don't add C to backstack??? thank you for your help — yeun hang yeung, Mar 22 '17 at 08:23
@yeunhangyeung Check this http://stackoverflow.com/a/12358563/3111083 . It would be better if you use fragments instead of activities. — Sunil Sunny, Mar 22 '17 at 09:00

score 0 · Answer 1 · answered Mar 22 '17 at 06:49

0

You should call finish() in activity C after, starting of activity D

startActivity(intent);
finish()

answered Mar 22 '17 at 06:49

Ufkoku

2,384
20
44

He can't destroy activity C, since there's an image there he want to save – Yash Mar 22 '17 at 06:49
He can use something to load image separately from activity, or use Picasso for example, it will cache image on disk – Ufkoku Mar 22 '17 at 06:53
Have method to save the image? If the image can save, finish() is ok. – yeun hang yeung Mar 22 '17 at 06:53
If you loading image from server, and you just don't want to waste user traffic again, you can use Picasso lib, it will cache image in RAM and disk. So the next load will be fast. – Ufkoku Mar 22 '17 at 06:57

score 0 · Answer 2 · answered Mar 22 '17 at 06:53

0

Handle onBackPressed() of each activity. So that after back pressing on D, it will redirect to B, then similarly to A.

answered Mar 22 '17 at 06:53

Sandeep Kharat

500
1
4
12

Can i just modify the code in ActivityC? Something like hide ActivityC in backtack – yeun hang yeung Mar 22 '17 at 06:55
Make a call to B in the the onBackPressed() of D. So it will redirect to B rather than C. and when you again call to existing C, it will come up with previous state. Just handle onBackPressed() of each activity to call existing activities from the satck – Sandeep Kharat Mar 22 '17 at 06:58
I think you should add launch modes to your answer. – Ufkoku Mar 22 '17 at 07:00
This will helpful: http://stackoverflow.com/questions/4038479/android-go-back-to-previous-activity – Sandeep Kharat Mar 22 '17 at 07:01
Because i am writing a library. The activityC is a library activity. I just can modify codes in library activity.So that, i cannot make change in B and D – yeun hang yeung Mar 22 '17 at 07:03

score 0 · Answer 3 · answered Mar 22 '17 at 06:55

Use onActivityResult() methods of an activity:-

Here is how it will work -

Use startActivityForResult() method while you are starting activity

While when you are going back
Activity D - before finishing write -

Intent i = getIntent();
setResult(RESULT_OK);
finish();

Your D is finished and c's onActivityResult() will be called - save your data and call finish() with above methodology, It will go to B's onActivityResult().

Android back stack

3 Answers3