A good understanding of the Activity life cycle is vital to ensure that your application provides a seamless user experience and properly manages its resources.
Android applications do not control their own process lifetimes; the Android run time manages the process of each application, and by extension that of each Activity within it. While the run time handles the termination and management of an Activity’s process, the Activity’s state helps determine the priority of its parent application. The application priority, in turn, influences the likelihood that the run time will terminate it and the Activities running within it.
The state of each Activity is determined by its position on the Activity stack, a last-in–first-out collection of all the currently running Activities. When a new Activity starts, the current foreground screen is moved to the top of the stack. If the user navigates back using the Back button, or the foreground Activity is closed, the next Activity on the stack moves up and becomes active.
Activity States:
As Activities are created and destroyed they move in and out of the stack. As they do so, they transition through four possible states:
-Active When an Activity is at the top of the stack it is the visible, focused, foreground Activity that is receiving user input. Android will attempt to keep it alive at all costs, killing Activities further down the stack as needed, to ensure that it has the resources it needs. When another Activity becomes active, this one will be paused.
-Paused In some cases your Activity will be visible but will not have focus; at this point it’s paused. This state is reached if a transparent or non-full-screen Activity is active in front of it. When paused, an Activity is treated as if it were active; however, it doesn’t receive user input events. In extreme cases Android will kill a paused Activity to recover resources for the active Activity.When an Activity becomes totally obscured, it is stopped.
-Stopped When an Activity isn’t visible, it ‘‘stops.’’ The Activity will remain in memory,retaining all state information; however, it is now a candidate for termination when the system requires memory elsewhere. When an Activity is stopped it’s important to save data and the current UI state. Once an Activity has exited or closed, it becomes inactive.
-Inactive After an Activity has been killed, and before it’s been launched, it’s inactive. Inactive Activities have been removed from the Activity stack and need to be restarted before they can be displayed and used.
Android applications do not control their own process lifetimes; the Android run time manages the process of each application, and by extension that of each Activity within it. While the run time handles the termination and management of an Activity’s process, the Activity’s state helps determine the priority of its parent application. The application priority, in turn, influences the likelihood that the run time will terminate it and the Activities running within it.
The state of each Activity is determined by its position on the Activity stack, a last-in–first-out collection of all the currently running Activities. When a new Activity starts, the current foreground screen is moved to the top of the stack. If the user navigates back using the Back button, or the foreground Activity is closed, the next Activity on the stack moves up and becomes active.
Activity States:
As Activities are created and destroyed they move in and out of the stack. As they do so, they transition through four possible states:
-Active When an Activity is at the top of the stack it is the visible, focused, foreground Activity that is receiving user input. Android will attempt to keep it alive at all costs, killing Activities further down the stack as needed, to ensure that it has the resources it needs. When another Activity becomes active, this one will be paused.
-Paused In some cases your Activity will be visible but will not have focus; at this point it’s paused. This state is reached if a transparent or non-full-screen Activity is active in front of it. When paused, an Activity is treated as if it were active; however, it doesn’t receive user input events. In extreme cases Android will kill a paused Activity to recover resources for the active Activity.When an Activity becomes totally obscured, it is stopped.
-Stopped When an Activity isn’t visible, it ‘‘stops.’’ The Activity will remain in memory,retaining all state information; however, it is now a candidate for termination when the system requires memory elsewhere. When an Activity is stopped it’s important to save data and the current UI state. Once an Activity has exited or closed, it becomes inactive.
-Inactive After an Activity has been killed, and before it’s been launched, it’s inactive. Inactive Activities have been removed from the Activity stack and need to be restarted before they can be displayed and used.
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