Implicit Intents & Explicit Intents | Android Application Development | Tutorial # 08

An Activity represents a single screen in your app with which your user can perform a single, focused task such as taking a photo, sending an email, or viewing a map. An activity is usually presented to the user as a full-screen window.

An app usually consists of multiple screens that are loosely bound to each other. Each screen is an activity. Typically, one activity in an app is specified as the "main" activity (MainActivity.java), which is presented to the user when the app is launched. The main activity can then start other activities to perform different actions.

Each time a new activity starts, the previous activity is stopped, but the system preserves the activity in a stack (the "back stack"). When a new activity starts, that new activity is pushed onto the back stack and takes user focus. The back stack follows basic "last in, first out" stack logic. When the user is done with the current activity and presses the Back button, that activity is popped from the stack and destroyed, and the previous activity resumes.

An activity is started or activated with an intent. An Intent is an asynchronous message that you can use in your activity to request an action from another activity, or from some other app component. You use an intent to start one activity from another activity, and to pass data between activities.

An Intent can be explicit or implicit:

An explicit intent is one in which you know the target of that intent. That is, you already know the fully qualified class name of that specific activity.
An implicit intent is one in which you do not have the name of the target component, but you have a general action to perform.
In this practical, you create explicit intents. You find out how to use implicit intents in a later practical.

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