Android: when should I use singleInstance launchmode

Question

There are four launch modes for an Activity, standard, singletop, singletask, and singleInstance. The previous three are relatively easy understanding and widely used. But till now, I did not find any scenario using singleInstance.

Some of the real use case is an Activity for Launcher or the application that you are 100% sure there is only one Activity

Have any one used it before?

refer http://stackoverflow.com/questions/3219726/android-singletask-or-singleinstance-launch-mode — sasikumar, Nov 29 '16 at 04:10
This might help : [Understand Android Activity's launchMode: standard, singleTop, singleTask and singleInstance](https://inthecheesefactory.com/blog/understand-android-activity-launchmode/en) — Sar, Nov 29 '16 at 05:08

score 2 · Answer 1 · answered Dec 29 '16 at 17:02

There is never a reason to use singleInstance launch mode.

If you are building a "home screen" replacement or a launcher type application, you would use singleInstance or singleTask launch mode to ensure that your Activity is always the root of its task. This makes sure that if another application launches your Activity, that Activity does not get launched into the task of the calling application and it also ensures that there is only ever one instance of your Activity created.

If you are writing a "home screen" replacement application, you can always make sure that no other activities get launched into your own task by always specifiying Intent.FLAG_ACTIVITY_NEW_TASK when launching other activities. In that case, you can use launch mode singleTask. So there is no reason to use launch mode singleInstance. But it probably wasn't clear to the original developers of Android at the time.

i used singleInstance and i want's clear that activity from backstack than what can i do ???? — Sagar Poshiya, Jul 15 '19 at 06:19
@SagarPoshiya Please open a new question and describe your problem. Asking a question in a comment here is not the right way to get help. — David Wasser, Jul 15 '19 at 08:51

score 1 · Answer 2 · answered Nov 29 '16 at 04:26

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SingleInstance launch mode should only be used in the applications that are implemented entirely as one activity. Only one instance will exist at a time. System will not launch any other activity into task holding this type. It is always a single member of its task and activities started from here will open into seperate task.

answered Nov 29 '16 at 04:26

Ritesh

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You don't need to use `singleInstance` launch mode to get this behaviour. Standard launch mode should give you this behaviour as well. In general it is a bad idea to use `singleInstance` launch mode unless you are building a "home screen" replacement. – David Wasser Dec 29 '16 at 16:54

Braj Bhushan Singh · Answer 3 · 2017-03-07T19:48:16.747

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singleInstance launchmode will be used when you do not want any other activity to be a part of the task.Its the only activity in the task. As this launchmode does not permit that.

edited Mar 07 '17 at 19:48

answered Nov 29 '16 at 05:33

Braj Bhushan Singh

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I don't really think this answers the question. It is too long and boring for me to even look at it to see if it is correct or not, but it doesn't answer OP's question, which is _"When should I use `singleInstance` launch mode?"_ – David Wasser Jan 06 '17 at 13:57
Edited answer.Check once again. – Braj Bhushan Singh Mar 16 '17 at 17:59
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Ok, why do you need to have only one activity in the task? Still does not answer the question :) – IliaEremin Mar 28 '17 at 16:17

Android: when should I use singleInstance launchmode

3 Answers3