In the Android Activity life cycle, under what condition is the onStop method invoked by the system?

Introduction / Context:
The Android Activity life cycle defines how Activities move between visible and non visible states. Understanding when onStop is called is essential for releasing resources and saving state correctly. This conceptual question checks whether you know when an Activity is considered stopped and how that relates to user visibility and navigation events.

Given Data / Assumptions:

• We are working with standard Activity life cycle callbacks in Android.
• The method of interest is onStop, which is part of the visible or non visible transitions.
• Another Activity might become visible, or the current Activity might be finishing.
• The goal is to identify the state in which onStop is invoked.

Concept / Approach:
The Activity life cycle can be summarized as moving through states such as created, started, resumed, paused, stopped, and destroyed. onStop is called when the Activity is no longer visible to the user. This happens when a new Activity completely covers it, or when the Activity is being finished and removed from the back stack. Developers use onStop to release resources that are not needed while the Activity is off screen.

Step-by-Step Solution:
Step 1: Recall that onStart and onResume are associated with the Activity becoming visible and then interactive.Step 2: When another full screen Activity is started, the current Activity goes through onPause and then onStop because it is no longer visible.Step 3: When the user leaves the Activity by pressing Back and the Activity is finishing, it also passes through onPause, onStop, and often onDestroy.Step 4: Therefore the defining condition for onStop is that the Activity is no longer visible, either due to another Activity covering it or because it is being finished.Step 5: This matches option C exactly.

Verification / Alternative check:
Android documentation clearly states that onStop is called when the Activity is no longer visible to the user. onStart and onResume are the callbacks for becoming visible and active, while onPause is for partial loss of focus. Comparing these definitions confirms that options referring to initial visibility or device reboot do not match the defined purpose of onStop.

Why Other Options Are Wrong:
Option A describes a state before the Activity becomes visible, which is associated with onCreate and onStart, not onStop. Option B describes the Activity becoming visible, again related to onStart or onResume. Option D introduces a condition about device reboot, which is unrelated to the normal Activity life cycle callbacks and is therefore incorrect.

Common Pitfalls:
Developers sometimes confuse onPause and onStop, using onPause to release heavy resources that should be released in onStop. Another mistake is to assume onStop will always be followed by onDestroy, which is not guaranteed if the system decides to recreate the Activity later. Correct use of onStop involves saving state and releasing non critical resources that are not needed when the Activity is off screen.

Final Answer:
When the Activity is no longer visible because another Activity comes in front of it or it is finishing.