launch modes are generally referred to the ways in which an activity is executed. it basically provides instruction on how the activity is associated with the current ongoing task.
there are two important concepts which are to kept in mind -
- task
- back stack
TASK
task refers to the number of activity associated with the app when the user interacts with it. whenever a user starts an application a new task is created, this task is the root of the first activity instance.
when a user launches new activity these activities combined to form a set of tasks which placed on one another.
BACK STACK
as soon as the startActivity() is called a new activity is created which are placed in a stack. when we end a current activity it moves back to the previous activity.
there are four types of launch modes -
- single top - in this mode, if the instance is already present in the top of the stack then no new instance is created. if there is no instance present then it will create a new one.
- single task - in this mode, a new task is created and the instance is pushed in the stack as the root. if the instance is present on separate task no new task will be created.
- single instance - this type of launch mode is used when the application has a single activity. this mode is similar to the single task except it does not create the activity in the same task.
- standard - this is the default launch mode in which a new instance is created from the activity it is launched from. there are multiple instances created and multiple instances are assigned to the similar or different task.
