This article explains how to resolve the error "Android SDK is out of date" when you start a new project in Android Studio.
Let's start a new project. Click on "New project" and a new project window should appear.
Ooops, what happened? What's that error message? This was really head-scratching for me because I don't have Eclipse on my machine. I began working for the first time on Android and this message says update your SDK. Now how to update the SDK, I Googled around and discovered that to update the Android SDK I must have the SDK Manager, now again where is the SDK Manager in Android Studio? I already installed it and I since learned that there is no SDK Manager present in the Android Studio, now the question is how to upgrade the SDK from version 21 to 22 as the message says. The simple answer is to go to
http://developer.android.com/sdk/index.html and download the ADT bundle or separately the SDK.
The ADT bundle includes (it's good if you are looking to use Eclipse also sometimes with Android Studio) the following:
One thing more, the reason why I said to download the ADT bundle instead of updating our SDK version is that by downloading only the SDK Manager, there are two reasons why I recommend downloading the complete ADT.
First Reason: Android Studio is currently available as an early access preview. Several features are either incomplete or not yet implemented and you may encounter bugs. So, if you are not comfortable using an unfinished product, then you should definitely go with the ADT bundle and start working using Eclipse.
Second Reason: Sometimes when you trying to upgrade your SDK version using the SDK Manager you might get the kind of error message that I got.
And to resolve this issue again you need to first upgrade your IDE that is Eclipse. How?
Step 1: Start Eclipse, go to "Help" then choose "Install New Software".
Step 2: Click "Add" in the top-right corner.
Step 3: In the Add Repository dialog that appears, enter "ADT Plugin" for the name and the following URL for the Location: https://dl-ssl.google.com/android/eclipse/ and press "Ok".
Step 4: In the Available Software dialog, select the checkbox next to "Developer Tools" and click "Next".
Step 5: In the next window, you'll see a list of the tools to be downloaded. Click "Next".
Step 6: Read and accept the license agreements, then click "Finish".
That's it; your IDE is upgraded.
Now if you upgrade your SDK version then it will be downloaded and installed. As in the procedure given below in this article.
And if you do not get that error message that I described in my second reason to download complete ADT, then simply upgrade your SDK version using the SDK Manager.
First, choose what you want to install with the Android SDK tool.
Accept the license and click on "Install".
Then you will be able to create projects in Android Studio. Click on "New project" and the new project template window will open and you can start your application.
Thanks