M-20 E pilot reported the landing gear collapsed during normal landing.

Narrative

The pilot of the subject aircraft entered the downwind leg for Runway XX at ZZZ. The pilot lowered the landing gear in the downwind leg and checked to ensure the gear was down and locked. The pilot confirmed the gear was properly in the extended position by forcefully pulling on the manual gear 'Johnson Bar'. The Johnson bar was found to be secure in the down and locked position when checked in this way on the downwind leg. The pilot then completed the landing pattern ultimately turning to the final leg. Following a normal and stabilized final approach; the pilot performed a smooth landing. The touchdown point of the landing was near the centerline and it was between the runway threshold and the 1000 foot runway markings. After touching down; the airplane began a normal rollout. After rolling for approximately 300 feet; the landing gear collapsed and the plane skidded to a stop. There were no injuries or property damages that are attributed to this incident with the exception of damage to the subject aircraft.There was no bounce on the landing and there was only very slight side loading on the gear at touchdown.The aircraft brakes were not utilized during rollout because the pilot had intended to perform and touch and go.Corrective actions for the aircraft could include an equipment inspection of the landing gear system including an inspection of the Johnson bar security while in the down and locked position. Also completion of an inspection of the green landing gear position light switch. Any causal equipment deficiency could then be corrected.Prior to the flight; the pilot self-checked fitness for flying by mentally performing the IMSAFE checklist. No factors affecting the quality of human performance were identified.Corrective actions for the pilot could include a routine second Johnson Bar check and observation of the green landing gear position light while on the Final leg for landing.