Android: permission denied for window type 2038 using TYPE_APPLICATION_OVERLAY

Did you request runtime permission by calling following intent?

private void requestOverlayPermission() {
    if (android.os.Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.M) {
        return;
    }

    Intent myIntent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION);
    myIntent.setData(Uri.parse("package:" + getPackageName()));
    startActivityForResult(myIntent, APP_PERMISSIONS);
}

Then in onActivityResult() check if Settings.canDrawOverlays(this) is true otherwise request permission again by calling above method.

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

I had the exactly same issue in service class(before and after Marshmallow).

if (Build.VERSION.SDK_INT >= 23) {
    if (!Settings.canDrawOverlays(this)) {
        Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
          Uri.parse("package:" + getPackageName()));
        startActivityForResult(intent, 1234);
    }
} else {
    startService(new Intent(SplashActivity.this,                     
    CheckServicesForApps.class));
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == 1234) {
            startService(new Intent(SplashActivity.this, 
            CheckServicesForApps.class));

    }
}

public class CheckServicesForApps extends Service {
    private Context context = null;

    @Override
    public void onCreate() {
        super.onCreate();

        ImageView imageView = new ImageView(context);
        imageView.setVisibility(View.GONE);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            try {
                windowManager = (WindowManager)getSystemService(WINDOW_SERVICE);

                //here is all the science of params
                final WindowManager.LayoutParams params = new WindowManager.LayoutParams(
                        WindowManager.LayoutParams.WRAP_CONTENT,
                        WindowManager.LayoutParams.WRAP_CONTENT,
                        WindowManager. LayoutParams.TYPE_SYSTEM_ERROR,
                        WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
                                | WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
                                | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON,
                        PixelFormat.TRANSLUCENT
                );

                windowManager.addView(imageView, params);
                hand=new Handler();

            } catch (Exception e) {
                hand=new Handler();
                e.printStackTrace();
            }
        }else{
            windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);

            final WindowManager.LayoutParams params = new WindowManager.LayoutParams(
                    WindowManager.LayoutParams.WRAP_CONTENT,
                    WindowManager.LayoutParams.WRAP_CONTENT,
                    WindowManager.LayoutParams.TYPE_PHONE,
                    WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
                    PixelFormat.TRANSLUCENT);

            params.gravity = Gravity.TOP | Gravity.CENTER;
            params.x = ((getApplicationContext().getResources().getDisplayMetrics().widthPixels) / 2);
            params.y = ((getApplicationContext().getResources().getDisplayMetrics().heightPixels) / 2);
            windowManager.addView(imageView, params);
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        /* We want this service to continue running until it is explicitly
        * stopped, so return sticky.
        */
        return START_STICKY;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();

        if (imageView != null) {
            try {
                windowManager.removeView(imageView);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        /**** added to fix the bug of view not attached to window manager ****/
    }
}

I had the exactly same issue. I guess you should differentiate the target (before and after Oreo)

int LAYOUT_FLAG;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
     LAYOUT_FLAG = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
} else {
        LAYOUT_FLAG = WindowManager.LayoutParams.TYPE_PHONE;
}

params = new WindowManager.LayoutParams(
        WindowManager.LayoutParams.WRAP_CONTENT,
        WindowManager.LayoutParams.WRAP_CONTENT,
        LAYOUT_FLAG,
        WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
        PixelFormat.TRANSLUCENT);