This sample demonstrates how you to change renderer of a sublayer in map image layer. Click on Apply renderer button to apply a class breaks renderer based on population for each county. Click on the Reset button to reset to original renderer.
How it works
The mapImageSublayers property on AGSArcGISMapImageLayer is used to get the Counties sublayer of type AGSArcGISMapImageSublayer. A new class breaks renderer is set on the sublayer via renderer property.