Kayteg is generally correct in that you don't want to charge with an extraordinary amount of amperage but if you have camper batteries paralleled to the truck batteries, with heavy wire, the batteries will attempt to equalize to the weakest one(s) and the alternator will take care of it.
If you want a set it and forget it setup, I'd suggest coming off a truck battery with a voltage sensing isolator like a Blue Seas ACR. When it senses charging voltage (truck running) it will latch and charge the camper. When voltage drops below 12.5V ( like shortly after truck is turned off)or something like that, it will disconnect from the truck batteries. Hook it up once and get full charging power from the alternator when the truck is running and auto disconnect.
It can work in reverse if the solar puts out enough voltage too. Idk what voltage solar charges at.