Nothing appears whilst attempting a render

instead of

 function onStart(state as Dictionary?) as Void{
        return new Kerror();
    }

try

function getInitialView()
{
  return [new Kerror()];
}

Thanks for the suggestion, but I'm still getting nothing. Even trying to render anything directly from that function with a "dc" implementation (

    class :APP: extends Application.AudioContentProviderApp{
/*
...
*/
    function getInitialView(dc){
        dc.setColor(Graphics.COLOR_PINK, Graphics.COLOR_PINK);
        dc.fillCircle(20, 90, 30);
    }
}

I'm sorry my mistake. I thought the Audio Content Provider works just like other types of applications, but not.
As I have no experience with Audio Content Provider, I can only help by referring you to

https://developer.garmin.com/connect-iq/connect-iq-faq/how-do-i-create-an-audio-content-provider/

And make sample app from "wizard" maybe it help.

_psx_ said:

And make sample app from "wizard" maybe it help.

Yeah, in VS Code, use the command palette: CTRL/CMD-SHIFT-P > Monkey C: New Project > [enter project name] > [select project type] Audio Content Provider

You'll see that the boilerplate for an audio content provider app is a bit different from what you (OP) have. e.g. This is what gets generated for the main app class:

import Toybox.Application;
import Toybox.Lang;
import Toybox.Media;
import Toybox.WatchUi;

class testmusicApp extends Application.AudioContentProviderApp {

    function initialize() {
        AudioContentProviderApp.initialize();
    }

    // onStart() is called on application start up
    function onStart(state as Dictionary?) as Void {
    }

    // onStop() is called when your application is exiting
    function onStop(state as Dictionary?) as Void {
    }

    // Get a Media.ContentDelegate for use by the system to get and iterate through media on the device
    function getContentDelegate(arg as PersistableType) as ContentDelegate? {
        return new testmusicContentDelegate();
    }

    // Get a delegate that communicates sync status to the system for syncing media content to the device
    function getSyncDelegate() as SyncDelegate? {
        return new testmusicSyncDelegate();
    }

    // Get the initial view for configuring playback
    function getPlaybackConfigurationView() as Array<Views or InputDelegates>? {
        return [ new testmusicConfigurePlaybackView(), new testmusicConfigurePlaybackDelegate() ] as Array<Views or InputDelegates>;
    }

    // Get the initial view for configuring sync
    function getSyncConfigurationView() as Array<Views or InputDelegates>? {
        return [ new testmusicConfigureSyncView(), new testmusicConfigureSyncDelegate() ] as Array<Views or InputDelegates>;
    }

}

function getApp() as testmusicApp {
    return Application.getApp() as testmusicApp;
}

This is what I get when I run the project without making any changes (I do have to turn off Monkey C type checking)

Also, a general observation. I noticed your code example looks like this:

dc.setColor(Graphics.COLOR_DK_GREEN, Graphics.COLOR_DK_GREEN);
dc.clear();
dc.drawText(132, 100, Graphics.FONT_SMALL, "asdasd", Graphics.TEXT_JUSTIFY_CENTER);

That's just going to result in a solid green screen (in any context where it works), because both the FG and BG color in dc.setColor() are the same. In general you would want to set the background color to either transparent or the color of your choice (e.g. white or black.)

e.g.

dc.setColor(Graphics.COLOR_DK_GREEN, Graphics.COLOR_TRANSPARENT);