What is the relationship between inflation and imports/exports? According to the aggregate demand curve, when the price level is higher, the real GDP demanded is lower. One of the explanations given is a consequence of the Mundell-Fleming model:

"As the price level drops, interest rates fall, domestic investment in foreign countries increases, the real exchange rate depreciates, net exports increases, and aggregate demand increases."

So this seems to suggest that increased inflation means more imports and less exports.

But increased inflation should also increase the exchange rate (currency depreciation). If you can trade foreign currency for more domestic currency, then exports should increase and (conversely) imports should decrease.

How do I reconcile these two models? Is this a difference of short run vs. long run? Or is it a matter of all other factors being held constant in each scenario?
As requested in comments:

It is a matter of which other factors are being held constant. If the relative-inflation-adjusted exchange rate (i.e. the real rate) stays constant, there may be no supply or demand effect on export and import volumes. 

However exchange rates do not exactly follow relative inflation in different economies; other factors such as interest rates and investment returns, balance of payments differences, and sentiment can also have an effect.