Black screen on app launch

It needs to be in a background service.  And in addition to the comm permission, you need the background permission.  To see a simple axample of how to do a background service, see 

https://developer.garmin.com/connect-iq/connect-iq-faq/how-do-i-create-a-connect-iq-background-service/#howdoicreateaconnectiqbackgroundservice

and this whole thread:

https://forums.garmin.com/developer/connect-iq/f/discussion/5287/very-simple-sample-of-a-watch-face-with-a-background-process

done ! Thx a lot for your help !

I'm having the same problem. My watch face works fine on MIP devices, but when I try to simulate it on an amoled device the screen is black. I've tried all the simulator settings and nothing changes. Profiler shows the code is running. What do I need to do different for amoled?

If you're not in low power mode, things should be the same.  If you are in low power on an amoled display, no more than 10% of the pixels can be on, or the screen will go black.

Have you used "View Screen Heat Map" in the sim?

If you have a flag for low/high power, you probably want to include logic if in low power and 

It starts black and stays black. I can toggle power mode but no effect. When I toggle hide/show screen goes from white/black. Heat map is grey, I click button and it's all green. CIQ 4.2 is same version as Fenix 7x on my wrist and code works fine on it. Code knows it's amoled (checking for burn in protection required) but I don't do anything with it right now. Var _awake set in enter and exit sleep is following power mode when I view memory. This is SDK 4.2.3 and VS 1.76.2 on Win 10. I've tried different amoled devices, at least the result is consistent so I hope it's just one fix for them all.

Remember, on AMOLED devices, onPartialUpdate is never called.

Add some println() calls or break points to make sure what you think is happening really is, including the colors you think you are using, and the x/y screen locations are correct.

onUpdate is getting called every second on startup, when I set low power mode it runs once per minute. All println outputs look normal, all screen coordinates are between 0 and screen dimensions, colors are by name from the basic 14 color palette used for MIP (is this a problem?) This watch face has so far been working on all the MIP simulator devices I've tried it on and the two MIP devices I own. It's black on both CIQ 3 and 4 amoled devices, so the difference in buffers doesn't seem to be the issue.

It's something in your code or the way you are doing something.  I have a number of watchfaces that support both MIP and AMOLDEL devices, and there are hundreds more in the store.

Do you use layouts, direct dc calls, or both?  If layouts, are you sure they are correct for the devices you are trying?

You can draw directly to the screen using the dc passed in onUpdate().

Buffered Bitmaps are different between CIQ4 devices and earlier.  The graphics pool. Even the call is different.