Run the timer in the background The extension has used background tasks 4.0.Discussion is accompanied by blocks and aia file

[Still-learning (1-2-3-4...)]

I advise you to do like this.

Get current time
Decide final time and convert into millis…save into tinydb

When screen inti or started timer, get current time(online time) convert into millis, then add +1000.

By using datetool extension you can find the difference between current time with tinydb final time and convert into HH mm ss without internet.

Simple…

Else test this APK

Countdown Timer

Have you tried already created extension? gsr_timer.apk (5.5 MB) This app is based on online time but stop button will be enabled after the timer over