In Friedel-Crafts alkylation of aniline, one gets:

Aniline does not undergo Friedel-crafts reaction due to salt formation with aluminium chloride, the Lewis acid, which is used as a catalyst, whereas aniline is a strong base. So, an acid-base reaction will take place. Thus, aniline reacts with $\mathrm{A}\mathrm{l}\mathrm{C}{\mathrm{l}}_3$ to form a salt.

Due to the positive charge on the nitrogen atom (shows $-\mathrm{I}$ effect and it is meta directing), electrophilic substitution in the benzene ring is deactivated. Hence, the Friedel-Crafts reaction will not take place in aniline.