Launch modes in Android

I am Naimish Trivedi, I have a vast experience in native and cross platform programming. I have presented the programming concept here in a simple and easy way from my experience. This will be very useful for developers.

Launch modes Introduction :

Launch modes in Android define how an activity is launched and what happens when a new instance of an activity is started. These modes are specified in the AndroidManifest.xml file within the <activity> tag, using the android:launchMode attribute. Understanding and correctly using launch modes can help manage the activity stack and provide a better user experience.

Types of Launch Modes :

• Standard
• SingleTop
• SingleTask
• SingleInstance

Standard LaunchMode :

• Default launch mode for activities in Android.
• New instance is created every time and placed on top of the stack.
• Suitable for scenarios where new activity instance is needed always.

A -> B -> C -> D

• Activity stack before launch Activity B.

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

• Activity stack after launch of Activity B. New instance of Activity B is created.

SingleTop LaunchMode :

• If an activity instance exists at top, it receives new intent via onNewIntent(), avoiding new instance creation.
• If activity is not on top, a new instance is created as usual.
• It prevents creating multiple instances of an activity.

• Activity B with SingleTop.
• If we try to launch Activity B again, then it will not be created. As its already on top

SingleTask LaunchMode :

• An activity declared with singleTask can have only one instance in the system.
• If the instance is already present then the onNewIntent() method will receive the callback.
• Suitable for activities that serve as entry points such as the app's main screen.

• Activity B with SingleTask.

A -> B -> C -> D

• Activity stack before launch of Activity B.

A -> B

• Activity stack after launch of Activity B.

SingleInstance LaunchMode :

• Similar to SingleTask, but with more restrictions.
• Launched activity is placed in a separate task, no other activities can be launched into the same task.
• Ideal for activities needing separate processes & independent interaction with the system, like dialer or home screen apps.

• Activity D with SingleInstance.

Task 1 : A -> B -> C

• Activity stack before launch of Activity D.

Task 2 : D

• Activity stack after launch of Activity D. New task created with Activity D.

Conclusion :

• Document the launch mode for each activity to ensure clarity and helps in future development.
• Test your activities behavior with various launch modes to ensure they meet the desired user experience.
• Use launch modes wisely, avoid using them as design or architectural work arounds.