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: 
If you updated to Android SDK Tools version 22.6, you are required to Update DDMS Tools and Plugins.

**Go to "Help Menu Bar" -> "Install New software" and install (this will update it) 
 url: <https://dl-ssl.google.com/android/eclipse/>**

Also update **"Developer Tools"** and **"NDK Plugins"** to latest Version.
This steps is useful for me and worked also.
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.