Long-term variations of 1A 0535+262 from 2010 to 2021. First panel: X-ray band light curves. The data from Swift-BAT and MAXI are labeled with red points and blue downward-pointing triangles, respectively. January 1 of each year is also marked at the top of the first panel. Second panel: barycentered and orbit-corrected spin-frequency history measured with Fermi-GBM. Third panel: equivalent widths of He I λ6678 lines. The data from this work are labeled with red points. The data from Moritani et al. (2013) are labeled with cyan stars. Fourth panel: long-term light curves of optical V band. The data from AAVSO, ASAS-SN, INTEGRAL-OMC, and this work are separately labeled with cyan upward-pointing triangles, blue leftward-pointing triangles, black pixels, and red points, respectively. In addition, the optical photometric data from Kondratyeva et al. (2020), Camero-Arranz et al. (2012) are labeled with green crosses and purple crosses, respectively. Fifth panel: long-term light curves of NEOWISE infrared magnitudes at 3.4 μm and 4.6 μm. These are labeled with black crosses and red points, respectively. Sixth panel: equivalent widths of Hα lines. Our data are labeled with red points. The data from Kondratyeva et al. (2020), Stoyanov & Zamanov (2016), Moritani et al. (2013), Camero-Arranz et al. (2012) are labeled with green crosses, blue crosses, cyan stars, and purple downward-pointing triangles, respectively. Seventh panel: evolution of (B − V) color index. The data from Kondratyeva et al. (2020), AAVSO, and this work are labeled with green crosses, cyan upward-pointing triangles, and red points, respectively. The vertical dash-dotted lines indicate the times of the NS periastron passages at the ephemeris of MJD 53613.0+111.1E (Finger et al. 1996); of those the gray lines are close to normal X-ray outbursts, and the red lines are close to giant X-ray outbursts. The vertical solid lines indicate the division of observations into four distinct periods.