onTaskRemoved() not getting called in HUAWEI and XIAOMI devices

On some devices (some LG, Huawei, Xiaomi, and others) your app needs to be manually added to a list of "protected apps" or "apps that are allowed to run in the background" in order for Android to restart STICKY services. If your app has not been manually added to this list, Android just kills your processes and does not restart them and also does not call onTaskRemoved(). This is done to preserve battery life by limiting the number of apps that can have STICKY services running in the background.

On such devices you should see a page in the "Settings", sometimes under "power management", sometimes other places, where you need to explicitly add your application. You'll also need to tell your users to explicitly add your app to this list.

When user has installed your app on xiaomi device, redirect user to auto start activity and tell user to switch on:

if (Build.BRAND.equalsIgnoreCase("xiaomi")) {                Intent intent = new Intent();                intent.setComponent(new ComponentName("com.miui.securitycenter", "com.miui.permcenter.autostart.AutoStartManagementActivity"));                startActivity(intent);            }

Use the above code to launch autostart activity page on xiaomi

I've been using onTaskRemoved() method in a Service to detect when an app was removed from device RECENT list by swiping it away.

With giving more light to the answer provided by David Wasser

It doesn't new on Xiaomi because Xiaomi has a feature called app permission, where a user has to allow the app to start automatically (Service). In your case the Service is not called, once its terminated from stack.

Go like this and allow your app to autostart:

Settings > permissions > Autostart