Cessna pilot reported an near midair collision event in the landing pattern.

Attributes
ACN	1742167
Time
Date	202005
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Cessna Aircraft Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	Final Approach
Route In Use	Visual Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	Takeoff
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Private Flight Crew Multiengine Flight Crew Instrument
Experience	Flight Crew Last 90 Days 13 Flight Crew Total 2522 Flight Crew Type 1833
Events
Anomaly	Conflict NMAC Deviation - Procedural FAR Deviation - Procedural Published Material / Policy
Miss Distance	Horizontal 500 Vertical 500

Narrative:

While nearing the approach on IFR flight to ZZZ I was cleared for the visual by center. Both center and myself were having communication difficulties generated by radio traffic on frequency. Center stated their current ATIS was dated and ZZZ tower was closed. Center gave cancelling instructions but I decided to cancel IFR at that time. While on approach I accessed ZZZ ATIS but allowed myself to be distracted by several targets on adsb. I made the mistake of assuming landings were runway xx; but in fact; one plane was in a left crosswind pattern for [runway] xyl and one plane was beginning takeoff roll from [runway] xyl. I had announced my arrival [on frequency] (tower). At the time of seeing the plane in the pattern; I did not realize it was in the pattern and assumed it was departing the airport area. On short final at approximately 300 feet AGL; I saw the other plane taking off from runway xyl become airborne. I immediately side-stepped north and then corrected and landed uneventfully on [runway] xxr. In retrospect; I should have approached what had become an uncontrolled airport with caution; determined the local traffic and the runways in use before committing to a final on [runway] xxr. I should also have monitored the ZZZ unicom frequency as well.

Original NASA ASRS Text

Title: Cessna pilot reported an NMAC event in the landing pattern.

Narrative: While nearing the approach on IFR flight to ZZZ I was cleared for the visual by Center. Both Center and myself were having communication difficulties generated by radio traffic on frequency. Center stated their current ATIS was dated and ZZZ Tower was closed. Center gave cancelling instructions but I decided to cancel IFR at that time. While on approach I accessed ZZZ ATIS but allowed myself to be distracted by several targets on ADSB. I made the mistake of assuming landings were Runway XX; but in fact; one plane was in a left crosswind pattern for [Runway] XYL and one plane was beginning takeoff roll from [Runway] XYL. I had announced my arrival [on frequency] (Tower). At the time of seeing the plane in the pattern; I did not realize it was in the pattern and assumed it was departing the airport area. On short final at approximately 300 feet AGL; I saw the other plane taking off from Runway XYL become airborne. I immediately side-stepped north and then corrected and landed uneventfully on [Runway] XXR. In retrospect; I should have approached what had become an uncontrolled airport with caution; determined the local traffic and the runways in use before committing to a final on [Runway] XXR. I should also have monitored the ZZZ Unicom frequency as well.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.