Question: I installed the ADT bundle from <http://developer.android.com/sdk/index.html> yesterday, and I was following a basic Hello World tutorial. I created a new Android Application Project with a Blank Activity named `MainActivity`. The resulting project has an empty `src` folder and empty `res\layout` folder. There is a `R.java` file in the `gen` folder but it has no reference to `MainActivity`. This is what the SDK manager says I have installed

* Android SDK Tools v 22.6
* Android SDK Platform-tools v 19.0.1
* Android SDK Build-tools v 19
* SDK Platform v 3
* ARM EABI v7a System Image v 2
* Android Support Library v 19.0.1
* Google USB Driver v 9

I also tried manually creating an activity by right clicking the `src` folder and going to Android Activity, but when I hit Finish on the creation wizard, nothing happens. Does anyone have any clues as to what's going on? Did I miss a key component to install or something?

Answer: 
The comment [see comment](https://stackoverflow.com/questions/22190578/adt-will-not-allow-creation-of-android-activity#comment33730649_22190578) by [NewShelbyWoo](https://stackoverflow.com/users/3382208/newshelbywoo) solved the issue
When you upgrade to SDK tools by 22.x you need to upgrade ADT plugin.
follow these steps to upgrade ADT:

Help > Install New software install 

add the below url and click on next.

url: <https://dl-ssl.google.com/android/eclipse/>.

But some times it complaining about conflicts, in that case,

First uninstall the existing ADT plug in. and try again.

To Uninstall Existing ADT plug in:

Help>About Eclipse Platform> and delete the pluging.

now follow the above steps.