Nikon D7000 autofocus does not focus

The autofocus moves closer and further, but it does not stop and it keeps becoming blurry. If i use manual focus the picture comes out great. But i don't want to have to use manual focus.focus mode is set to af-f. It may focus on walls and floors sometimes but rarely.

Autofocus needs something with contrast to focus on. A wall or floor usually is just an area of the same color, so it can't lock on. Also, these are indoor things, and autofocus works best with lots of light available - typically the light is very dim indoors compared to outdoors.

Try autofocusing on something with lots of contrast, e.g. An open page of a book or newspaper. It should work perfectly then. If it does not, *then* there's an issue. But if it does, then probably you probably want your camera's AF system to do something that it isn't designed to do.

A few questions:
Is your lens fully into the auto focus setting?

What is AF-F? I thought Nikon had AF-S, AF-C and AF-A? AF-S is single-it focuses one time and locks when the shutter is pressed half way. Great for portraits or when you want to lock your focus and still move your camera.AF-A is auto-your camera gets to choose if it wants to use AF-c or AF-S. Not a wise choice. Cameras notoriously make the decision that we would not make.AF-C is continuous. It continuously focuses on your subject. Great for sports or following a moving subject.

Are you using all of the focus points or just one? You want to only use one and lock it where you want to focus. If you are using all, the camera gets to pick where it wants to focus and lock there. Pot luck what it decides.

Are you shooting in a low light situation? Your camera can't see in the dark.cameras depend upon light. Some lenses will focus better in low light than others, but in general you just can't focus in the dark. You must have contrast to focus.

Try shooting under more light.AF only works with good contrast scenes which comes with better light quality.