How does the Android system determine the need to start a new Activity?

In Android, the need to start a new Activity is determined by the system based on the Intent created by the application. When the startActivity(Intent) method is called, the system analyzes the Intent and decides which Activity to launch. If the Intent explicitly specifies a particular Activity, the system creates and launches it. If the Intent is implicit, the system searches for a suitable Activity registered in the manifest with a matching Intent filter.

The system also considers the current task stack (back stack) and Intent flags, such as FLAG_ACTIVITY_NEW_TASK or FLAG_ACTIVITY_CLEAR_TOP, to determine whether to create a new Activity or use an existing one.

Example of launching an Activity:

Intent intent = new Intent(this, DetailActivity.class);
startActivity(intent);