Launch Modes in Android

Overview

Standard: A new instance is created every time.
SingleTop: Reuses the activity if it's already at the top of the stack.
SingleTask: Clears everything above the existing activity instance in the stack.
SingleInstancePerTask: Creates a new task for each instance, ensuring independence.

Task

A task consists of a collection of activities that users engage with while performing specific actions within your app.
Activities within a task are arranged in a structure called the backstack.
Backstack maintains activities in the order in which they are launched.
Launch modes allow you to specify how a new activity instance is linked to the existing task.

It can be defined in 2 ways:

Using Manifest.xml file
Using intent filters
Types of Launch Modes

standard
singleTop
singleInstance
singleTask
singleInstancePerTask
standard

default launch modes
creates a new instance everytime in the task.
The task with activities:

A -> B -> C -> D

Start new activity E:

A -> B -> C -> D -> E

Again start activity B:

A -> B -> C -> D -> E -> B

singleTop

a new instance is created if the activity is not at the top of the stack
onNewIntent() is called if activity is at the top
The task with activities:

A -> B -> C -> D

Start new activity E:

A -> B -> C -> D -> E

Again start activity E:

A -> B -> C -> D -> E

onNewIntent() of Activity E is called

Again start activity C:

A -> B -> C -> D -> E -> C

singleTask

activity’s instance is created once in a lifetime
activities on top are removed and onNewIntent() is called
The task with activities:

A -> B -> C -> D

Start new activity E:

A -> B -> C -> D -> E

Again start activity C:

A -> B -> C

onNewIntent() of Activity C is called. Activity D & E is removed.

singleInstance

activity is created in new task
no other activities can be added to the task
if activity is already present then it is reused
single activity instance will be used in whole system.
The task with activities:

A -> B -> C -> D

Start new activity E:

Task 1 : A -> B -> C -> D

Task 2 : E

Again start activity E:

onNewIntent() of Activity E is called. No new task will be created

singleInstancePerTask

one instance of an activity per task
allows other activities to exist in same task
onNewIntent() is called if activity is called in same task
The task with activities:

A -> B -> C -> D

Start new activity E:

Task 1 : A -> B -> C -> D

Task 2 : E

Again start activity E from Task 2:

Task 1 : A -> B -> C -> D

Task 2 : E

onNewIntent() will be called on Activity E in Task 2.

start activity E in new task:

Task 1 : A -> B -> C -> D

Task 2 : E

Task 3 : E

Ways to define launch modes

Using Manifest file

standard

<activity android:name=".MainActivity" android:launchMode="standard" />
singleTop

<activity android:name=".MainActivity" android:launchMode="singleTop"/>
singleTask

<activity android:name=".MainActivity" android:launchMode="singleTask"/>
singleInstance

<activity android:name=".MainActivity" android:launchMode="singleInstance" />
singleInstancePerTask

<activity android:name=".MainActivity" android:launchMode="singleInstancePerTask" />
Using intent flags

standard

val intent = Intent(this, MyActivity::class.java) 
startActivity(inte
*No intent flag is required

singleTop

val intent = Intent(this, MyActivity::class.java) 
intent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP)
startActivity(intent)
singleTask

val intent = Intent(this, MyActivity::class.java) 
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
startActivity(intent)
singleInstance

val intent = Intent(this, MyActivity::class.java) 
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_MULTIPLE_TASK) 
startActivity(intent)
singleInstancePerTask

val intent = Intent(this, MyActivity::class.java) 
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_DOCUMENT or Intent.FLAG_ACTIVITY_MULTIPLE_TASK) 
startActivity(intent)
Jetpack Compose

standard

navController.navigate("destination")
singleTop

navController.navigate("destination") { launchSingleTop = true }
singleTask

navController.navigate("destination") {
popUpTo("destination") { inclusive = false } launchSingleTop = true }
singleInstance / singleInstancePerTask

Not directly supported as compose focuses on single activity using NavHost and NavContoller API.