Different Types of Activities in Android Studio

In Android, an "Activity" represents a single screen with a user interface. While the core concept of an "Activity" remains consistent, based on its purpose and how it's used, activities can be categorized in various ways. Here are some classifications based on their usage and behavior:

Standard Activity:
- This is the default and most commonly used type.
- Represents a typical screen that users see when they interact with an app.
SingleTop Activity:
- If an instance of the activity already exists at the top of the current task and the system routes the intent to this activity, no new instance will be created because it will fire off an onNewIntent() method.
- Useful for cases where multiple instances should be avoided like viewing a notification.
SingleTask Activity:
- A new task will always be created and a new instance will be pushed to the task as the root. However, if any activity instance exists in any tasks, the system routes the intent to that activity instance through the onNewIntent() method, thereby not creating a new instance.
- It's like having a unique instance of the activity.
SingleInstance Activity:
- Same as singleTask, but the system doesn't launch any other activities in the same task. Any activity started by this one opens in a separate task.
Dialog Activity:
- This isn't a formal type like the above, but rather an activity styled to look like a dialog using themes.
- Appears as a dialog rather than occupying the entire screen.
ListActivity:
- This is a subclass of Activity that's been around since the early days of Android.
- Used to display a list of items by binding to a data source such as an array or a cursor, without needing to use a ListView.
TabActivity:
- Another older subclass of Activity used to deal with tab-based UIs.
- Deprecated in favor of newer UI patterns and the Fragment system.
ExpandableListActivity:
- Like ListActivity, but designed to work with expandable lists/ExpandableListView.
PreferenceActivity:
- An activity that displays settings or preferences to the user as a list of options.
- Before the introduction of the Preference Fragment and PreferenceScreen for better modular preferences, this was the go-to way of creating preference screens.
FragmentActivity:
- This isn't a distinct type of Activity but is worth mentioning. It's part of the AndroidX library and provides compatibility support for fragments.
- Often used as a base activity when using fragments, especially before fragments were included in the core Android framework.

The behavior of an activity, especially how it's instantiated or how it responds to new intents, can be controlled using the launchMode attribute in the Android Manifest. It's this attribute that can be set to values like standard, singleTop, singleTask, or singleInstance to determine the activity's behavior.

Remember, while there are various types of activities and behaviors you can utilize, always aim for the simplest design that meets your app's needs. Overcomplicating an app's navigation stack can lead to confusion for both developers and users.