Android default launchMode of LAUNCHER activity?

Question

does the launchMode of the launcher activity in the manifest get ignored? The android documentation says that the default

Answer 1

You are confusing two things. One is launchMode and the other is "what happens when the user selects an app icon from the HOME screen, or selects a task from the list of recent tasks". These are 2 completely different things.

launchMode

Each Activity has a specified launchMode (the default is "standard" or "multiple". This tells Android how to start this Activity, and there are many factors that can contribute to the "interpretation" of the launchMode. It depends on what other flags may have been specified in the Intent used. It depends on which task requested the launch of the Activity (or if the launch was requested from a non-activity context, like from a Service or BroadcastReceiver). It depends on whether or not an existing instance of the Activity is already active in the specified task, etc.

Behaviour on selecting an app icon from the HOME screen or list of installed applications

When the user selects an app icon, startActivity() is called with an Intent containing the following data:

• ACTION=MAIN
• CATEGORY=LAUNCHER
• Component is set to the package name and the class name of the Activity that is defined in the manifest with ACTION=MAIN and CATEGORY=LAUNCHER
• Flag FLAG_ACTIVITY_NEW_TASK and FLAG_ACTIVITY_RESET_TASK_IF_NEEDED are set.

Regardless of the launchMode definition of the Activity to be launched, calling startActivity() with an Intent like this causes the following behaviour:

If there is already an existing task whose task affinity matches the Activity being started (in simple terms, if the app is already running), Android will simply bring the existing task to the foreground. That's it. It doesn't create an instance of any Activity. It doesn't call onNewIntent() on any Activity. It does nothing other than bringing the existing task to the foreground. This is why, even if you specify launchMode="standard" for your launcher Activity, Android doesn't create a new instance every time you click on your app icon.

If there isn't already an existing task whose task affinity matches the Activity being started (in simple terms, if the app isn't already running), Android will create a new task and launch the Activity into that task. launchMode doesn't play a role here, since there is absolutely no difference between the launch modes when launching a single Activity into a new task. Android always creates a new task and always creates a new instance of the Activity as the root of that task.

This behaviour is also the same when the user selectsa task from the list of recent tasks. If the task is still running, Android just brings the task to the foreground, does not start any new Activity instances and does not call onNewIntent(). If the task is no longer running, Android creates a new task and launches the launcher Activity into that task. The only difference here is that the flag FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY is also set in the Intent if the user selected a task from the list of recent tasks.

I hope this answers your question.

See this answer for a very detailed explanation of FLAG_ACTIVITY_RESET_TASK_IF_NEEDED and task reparenting in general.