Someone recently asked on Zhihu: “How to calculate APK startup time?”

“How can I use Python or direct ADB commands to calculate APK startup time? I want to measure the time from clicking the icon to the APK being fully started. For example, in a game, this would be from the icon tap to entering the login screen. Existing methods like adb shell am start -W provide ThisTime and TotalTime, but I’m unsure of the difference and they don’t seem to match visual reality.”

My colleague Guo Qifa and I answered different parts of the question. With his permission, I put our answers together here: partly so I could find them again, and partly to make them easier for other developers to find outside Zhihu.

In the previous article, we tried the third DelayLoad approach. That article showed the code; here I want to follow what happens when it runs.

That takes us through several Android framework classes and Activity lifecycle methods.

I found tracing it quite fun: use the tools, add some debug code, and follow it one step at a time. Doing that helped me understand Activity startup better. I hope walking through it helps you too.