Gitignore not working

My .gitignore file isn't working for some reason, and no amount of Googling has been able to fix it. Here is what I have:

*.apk
*.ap_
*.dex
*.class
**/bin/
**/gen/
.gradle/
build/
local.properties
**/proguard/
*.log

It's in the directory master, which is my git repo. I'm running Git 1.8.4.2 because I'm on a MacBook running OSX 10.8.6.

The files/folder in your version control will not just delete themselves just because you added them to the .gitignore. They are already in the repository and you have to remove them. You can just do that with this:

Remember to commit everything you've changed before you do this!

git rm -rf --cached .
git add .

This removes all files from the repository and adds them back (this time respecting the rules in your .gitignore).

To untrack a single file that has already been added/initialized to your repository, i.e., stop tracking the file but not delete it from your system use: git rm --cached filename

To untrack every file that is now in your .gitignore:

First commit any outstanding code changes, and then, run this command:

git rm -r --cached .

This removes any changed files from the index(staging area), then just run:

git add .

Commit it:

git commit -m ".gitignore is now working"