Error: failed to find target with hash string 'android-21'

Question

I want to change my compileSdkVersion from 23 to 21.So I have made following changes in the build.gradle but I am getting following error.How can I resolve this?

Answer 1

Note: I think this might be a bug in Android Studio.

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1. Go to Project Structure
2. Select App Module
3. Under the first tab "Properties" change the Compile SDK Version to API XX from Google API xx (e.g. API 23 instead of Google API 23)
4. Press OK
5. Wait for the completion of on going process, in my case I did not get an error at this point.
6. Now revert Compiled Sdk Version back to Google API xx.

If this not work, then:

7. With Google API (Google API xx instead of API xx), lower the build tool version (e.g. Google API 23 and build tool version 23.0.1)
8. Press Ok and wait for completion of on going process
9. Revert back your build tool version to what it was before you changed
10. Press Ok and Wait for the completion of process.
11. Done!