Do frogs have no predators?

They certainly have predators.  They also have camouflage.  The frog hopes you don't notice it.

They can just smell the bi+ch in you.

as the other guys already said,i think frogs dont care so much about human presence even because they're already used to us due to seeing us everyday and some people wandering around and bothering them

Lots of predators eat frogs. Birds, snakes, big frogs, coyotes, skunks, raccoons, turtles, fish, bats, and of course people eat frogs. 

Storks, birds of prey, crows, gulls, ducks, terns, herons, pine martens, stoats, weasels, polecats, badgers, otters and snakes are all predators of frogs.

Birds, snakes, big fish, other frogs, raccoons...  Really any predator larger than a frog will eat a frog.   Some frogs will cannibalize smaller frogs.   There are snake species that specifically prefer amphibians over rodents (hognose snakes, for example, prefer frogs)

herons are important predators as are a number of land animals (many mammals) and other birds, and even some fish.  Clearly, if the frog did not flee, it was either incapacitated or had learned to not fear humans.