Can't install ADT onto Eclipse

I realize my question seems related to others asked on this page, but my problem is different than all the other ones I've seen.

I've downloaded Eclipse and Android ADT Plugin for my Mac.

Eclipse opens fine, yet something like this happens when I try to install the ADT plugin:

I tried later to do this with http: instead of https:, and it let me continue to the install page, but said everything was installed. So, assuming it truly is installed, I continued by going into 开发者_Python百科Eclipse's preferences and adding the android sdk location to it. However, it will now show up blank, like this:

.. with that error message below it. It tells me to use the SDK manager to install it, but clearly it says everything is already installed.

Any ideas of what I should do? Thank you.

Fire up the SDK Manager, either via the android application inside the ANDROID_SDK/tools folder or from eclipse via Window -> SDK and AVD manager, go to Available packages, open the Android Repository tree and install the platform tools package (probably along some target platforms if you got none - if you got a decent net connection, just get the whole tree, so you won't be bugged with missing targets for testing later).