<qa>  What is the primary outcome measure of the study?This study takes Rate of stone recurrence as primary outcome measure, by random, blank control, and multicenter clinical trial design method, assess the efficacy and safety of potassium citrate extended-release tablets on Urolithiasis formation or recurrence, provide evidence for drug re-registration, and observe its efficacy on Urinary calculi such as renal tubular acidosis with calcium stone, and uric acid stones with or without calcium stone, urinary tract stone of effectiveness. 