Difference: The so-called hot start is still in the background process after the app exits, and then click the APP icon to start quickly! Cold start is when the app exits the background completely and needs to be re-executed from application when the app icon is clicked! How it works: The cold start time is the time between when the user clicks on your app and when the system calls activity.oncreate (). During this time, WindowManager loads the windowBackground in the App theme style as the app preview element, and then loads the activity layout