Build unsuccessful : Error with Android project in Xamarin.Forms

Question

I just create a small Xamarin.Forms sample application. When i build my Android project i get some errors. I just googled errors and find some solutions. But nothing works f

Answer 1

EDIT: This information is now included in our documentation: https://developer.xamarin.com/guides/android/troubleshooting/resolving-library-installation-errors/

Xamarin.Android Support Library NuGet m2repository fixes

1. Investigation

You may run into issues with downloading the m2repository when referencing a NuGet package of the Android Support Libraries / Google Play Services.

Example error:

Download failed. Please download https://dl-ssl.google.com/android/repository/android_m2repository_r25.zip and put it to the C:\Users\[Username]\AppData\Local\Xamarin\{SUPPORT LIBRARY NAME}\{VERSION NUMBER} directory."

Mac Directory: /Users/[Username]/.local/share/Xamarin/

Windows Directory: C:\Users\[Username]\AppData\Local\Xamarin\

2. Folder Contents

This example will be using Windows paths. This can be applied to either OS.

• Given the following: C:\Users\[Username]\AppData\Local\Xamarin\

• A folder for each of the respective Android Support Libraries / Google Play Services will be shown.

• Each library should have a collection of versions:

Note: In this example I'm showing all of the versions of Android.Support.v4

• We will then investigate the respective version we're interested in. We should see two folders inside, content and embedded:

1. content - Contains the m2repository
2. embedded - Contains the respective .aar contents

3. Automatic Fix

• Delete the versioned library folder that is giving you errors:

Mac Directory: /Users/[Username]/.local/share/Xamarin/{SUPPORT LIBRARY NAME}/{VERSION NUMBER}

Windows Directory: C:\Users\[Username]\AppData\Local\Xamarin\{SUPPORT LIBRARY NAME}\{VERSION NUMBER}

• Rebuild your project (Which will kickoff a Build Task to re-download the library).

4. Manual Fix

There are two steps to manually fixing this error.

1. Adding the m2repository folder to the /content folder.
2. Adding the respective Android Support Library / Google Play Services .aar contents to the /embedded folder.

1. Adding the m2repository to the /content folder

Download the respective m2repository from google.

https://dl-ssl.google.com/android/repository/android_m2repository_r25.zip

Note: This version number will vary based on your error message.

• Extract that .zip to any directory. There should now be a android_m2repository_r25 folder.
• Inside the android_m2repository_r25 folder, we have a m2repository folder.
• Place the m2repository into the {VERSION NUMBER}/content folder

2. Adding the .aar contents to the /embedded folder

• Inside the m2repository folder, there is an .aar for the support library to be resolved. It can be found in the com\android\support directory:

Example:

m2repository\com\android\support

• There should be a support-v4\{VERSION NUMBER} which will contain the .aar file.
• Extract the .aar and put the contents into the embedded folder.

Example:

• m2repository\com\android\support\support-v4\23.1.1\support-v4-23.1.1 will contain items such as a aapt, aidl, assets, libs, res, AndroidManifest.xml, annotations.zip, and classes.jar.
• Place all of the contents into the {VERSION NUMBER}/embedded folder.

5. New Manual Fix

• Get the URL of the missing m2repository download
• Use a MD5 hash on the download URL
• Rename the file to {MD5HASH}.zip (Where MD5HASH is the hashed download URL)
• Place the new hashed .zip file in your Xamarin\zips directory