Does diversity in undergraduate research topics look bad on my graduate school application?
Trying out several projects in different areas does not necessarily say that you do not know what interests you. You have to show them that you are interested in several areas and that you wanted to get an insight in order to obtain a wider range of possibilities.
I think that there are few people who immediately find the right area that fully interests them. It is important that you present it that way. Working on different projects brings more extensive experience in any case.
If you have then found the right area, you can deal with it more intensely.