Can pvc fittings and pvc pipe be used to install tube and shower fixture
I might be confusing PVC with CPVC.  They're both plastic pipes that are glued together, but they are different products.

PVC can be used only for drain lines (including indoors, despite what the answer below says). If you want to use it for your tub and shower drain, you can.

CPVC can be used for water supply lines, and you can use it for the connection between the shower valve and the shower spout.  However, you should not use CPVC for the connection between the valve and the tub spout.  The reason is that CPVC has a narrow diameter and might restrict flow out of the tub spout, causing some water to leak out of the shower instead.

You'll also want to make sure your valve accepts CPVC connections.  If it has brass or Pex connections, you'll need to use an adapter; you can only glue CPVC to CPVC.