Android xbuild: 'OutputPath' property is not set

Background

My team and I are building a Xamarin Forms mobile application that includes iOS and Android projects. I've set up automated CI builds and I've created some custom build configurations for CI and Production (Store) builds. The idea is to use one solution level build configuration that configures both iOS and Android projects appropriately with one build script.

Here's the Ad-hoc (deploy to test devices) Build Config:

(The first project is the PCL which simply the App name with no suffix).

Here's the Production (Store) Build Config:

This all works great in Visual Studio. But not in Bitrise (my chosen online mobile build system).

The Error Message

Here's the command line used to build the Android project extracted from the build output in Bitrise:
xbuild /t:PackageForAndroid /p:Configuration"PlayStore" "./XXXXXXXX/XXXXXXXX.Droid/XXXXXXXX.Droid.csproj" /verbosity:minimal /nologo

Within a few seconds produces this error message.
/Library/Frameworks/Mono.framework/Versions/4.4.0/lib/mono/4.5/Microsoft.Common.targets: error : 'OutputPath' property is not set for this project. Usually this is caused by invalid Configuration/Platform combination. Original values: Configuration: PlayStore Platform: AnyCPU.

There's been reports of this error on the Xamarin Forums (and here) that include other build system like Jenkins.  It looks like there has been bugs in xbuild and Xamarin Studio that have been investigated and fixed.  So its no fault of Bitrise.

The build is given "AppStore" as the target build config, and "RealDevices" as the platform.  The solution file is successfully parsed and based on what we can see from the command line above, it has passed the right target and platform to xbuild (see Store Build Config screenshot above).

The iOS project builds fine.

The diagnostic process on Bitrise

It seems unlikely that the bugs discussed in the forum posts mentioned above are still a problem, the posts are dated some time ago. The suggestions center around App code problems rather than real bugs with Xamarin or Mono.

Bitrise only offers limited options to pass parameters to the Xamarin-Builder step. Basically only build configuration, platform, and solution path.  This is where their generic Script step comes in handy.  Delete the Xamarin-Builder step and replace it with the Script step and use the command line to invoke xbuild directly:

xbuild /t:PackageForAndroid /p:Configuration="PlayStore" /p:Platform="AnyCPU" "./XXXXXX/XXXXXXXX.Droid/XXXXXXXX.Droid.csproj" /verbosity:detailed /nologo /p:OutputPath="bin/PlayStore"

This produced the same results, with nothing new of value.

Running it locally on a Mac also produced the same results.

I then realised that because the build of the Android project is triggered with a build config of "PlayStore" it is passing this value to the its dependency the PCL project.  But its supposed to be built in "Store" config according to the solution file. It doesn't have a config in it's csproj file named "PlayStore" hence the error.

The Solution

xbuild is not building the solution in the same was as msbuild, Visual Studio or Xamarin Studio.  It is using the Android csproj file as its entry point not the solution file.  So the Build Config name provided to build the Android project has to be the same Config name provided to build the PCL.

I added a "PlayStore" Build Config to the PCL and bingo. 

The only downside is that I have two Build Configs to maintain for the PCL: PlayStore and AppStore.

AndroidDeploymentException: [INSTALL_FAILED_UPDATE_INCOMPATIBLE]

Xamarin.AndroidTools.AndroidDeploymentException: InternalError ---> Mono.AndroidTools.InstallFailedException: Failure [INSTALL_FAILED_UPDATE_INCOMPATIBLE]

I've come across this problem several times with different physical Android devices.  This message is thrown when a real production Google Play App with the same App Id has been installed and then you try to install a debug version.  It will happen with any means of deploying a debug version including with Visual Studio, Xamarin Studio, and the command tools.

I think what is happening is that Android is not happy with a debug version being deployed over the top of a properly signed and deployed version of a Play Store App.  Android stores a flag to block further install attempts for that App Id.  When an App deployment attempt is made, the flag that Android created is not reset.

To fix this, you will need to reinstall the App from Google Play and then uninstall it normally. After that you'll be able to debug your App with Visual Studio.

How to create a signed and aligned APK using Visual Studio

This article guides you through creating an APK file for your Xamarin.Android App that is ready to publish on Google Play.

Creating an Android APK that is signed and aligned can mostly be achieved with Visual Studio.  To sign it and align it, command line tools must be used, but the APK can be created with Visual Studio.

You're App does need to be signed to be submitted to Google Play, but it doesn't necessarily need to be "aligned".  It is highly recommended however. Its basically a very cheap optimisation that will minimise the amount of RAM your App will need at runtime.

Step 1 - Prepare your App for Release

This is out of scope for this article. Check out this link:

Xamarin Guide

Step 2 - Build a Release build of your App

Build your Android App in Release Mode.  Ensure the platform drop down is set to "Any CPU".

Step 3 - Export to APK

This does not automatically occur when you build a Release build. Creating the APK must be triggered manually by selecting a context menu item when you right click the Android Project in Solution Explorer.

The APK will be created in your bin\Release\ folder for the Android project.

Step 4 - Sign the APK

Google Reference

Ensure you have the JDK path in your environment Path variable.  My JDK is installed here:
C:\Program Files (x86)\Java\jdk1.7.0_55\bin

The "signed" file you see in the folder has been automatically signed with a Developer certificate.  This isn't suitable for publishing purposes, so you'll need a certificate that identifies you as a developer.

To sign your APK, you'll need your Java KeyStore (JKS) file.  These files usually have a JKS extension or a keystore extension.  If you don't have one you can create one using the instructions in the Google reference above. In summary the command line is: keytool -genkey -v -keystore my-release-key.keystore -alias alias_name -keyalg RSA -keysize 2048 -validity 10000

Once you have a JKS file you need to keep it in a safe place you must use the same file to sign your App everytime. This file uniquely identifies you as a developer.

jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore my-release-key.jks my_application.apk alias_name

There are three things you need to specify in this command:
Replace "my-release-key.jks" with the filename to your JKS file.
Replace "my_application.apk" with your app's APK filename.
Replace the "alias_name" with the alias name you used when creating your JKS file.
You'll also be prompted for the keystore password.

Step 5 - Align the APK

Finally use the Zipalign tool to optimise your APK file.
Zipalign isn't in the same folder as the JDK, for me its in the Android tools folder here:
C:\Program Files (x86)\Android\android-sdk\build-tools\22.0.1
This also should be added to your environment path if it isn't already.

zipalign -v 4 my_application.apk my_application_aligned.apk


That's it.

Verify an APK is signed with correct certificate

How do I determine if the APK produced by the build system has been signed correctly with the production certificate?

jarsigner -verify -verbose -certs my_application.apk >output.txt

You will need to ensure that the java jdk is included in your Path.  You'll find it, here:
C:\Program Files (x86)\Java\jdk1.7.0_55\bin\jarsigner.exe
If you don't then its likely you haven't correctly installed the Android SDK.

This will produce a lot of output that will show the certificate used to sign each file, which is usually the same certificate.  Open the output.txt file with a text editor.

s      98829 Mon Jul 18 15:45:06 NZST 2016 META-INF/MANIFEST.MF

      X.509, CN=CERTIFICATE_NAME, OU=Department, O=Company Ltd, L=Auckland, ST=Auckland, C=NZ
      [certificate is valid from 01/01/16 10:06 PM to 31/12/43 11:06 PM]
       98950 Mon Jul 18 15:45:06 NZST 2016 META-INF/CERT.SF
        1408 Mon Jul 18 15:45:06 NZST 2016 META-INF/CERT.RSA
sm      7364 Wed Dec 31 16:00:00 NZDT 1980 AndroidManifest.xml

      X.509, CN=CERTIFICATE_NAME, OU=Department, O=Company Ltd, L=Auckland, ST=Auckland, C=NZ
      [certificate is valid from 01/01/16 10:06 PM to 31/12/43 11:06 PM]

Ensure the certificate name is what you expect, and there is no mention of "Debug" in the output file.

I find it useful to do a search and replace for the "CN=CERTIFICATE_NAME" part, and replace with "@@@@@@" or whatever.  Then search for "CN=", and find any, that means some files are signed with a different certificate.

A fun build trist: Xamarin.iOS, a provisioning profile, and a certificate

A [sarcasm]fun[/sarcasm] problem to have:

/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets : error: No installed provisioning profiles match the installed iOS signing identities.

I use Bitrise for my mobile CI.  While its a great system, sometimes opaque errors can increase your blood pressure.  Honestly, its not any fault of Bitirse, its more a Xamarin problem in general and the maturity of the tool-sets.

For my error I had created my Apple certificate and provisioning profile in the Apple Developer portal with no issues.  I always download and install the certificate (a development certificate in my case) onto my Mac's Keychain.

For Bitrise you need to export the p12 file for the certificate and upload into Bitrise:

Here you can see I've uploaded both the certificate and the provisioning profile and I've saved the password. All good so far.

After still getting the error from Bitrise:

/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets : error: No installed provisioning profiles match the installed iOS signing identities.

I forced the selection of the correct certificate in the iOS project properties:

Still no luck.

Next I decided to explicitly set the provisioning profile so it's not using "magic" to determine which profile to use.

Visual Studio doesn't seem to understand or recognise the list of valid provisioning profiles however, as for me, the drop down list is blank.  Nevermind, it can be set in the XML.

First get the provisioning profile ID from your provisoning profile file. Its a file with the extension .mobileprovision, that you download from the Apple Developer portal.  Find a section in the XML that has a key "UUID".  Next to it is the Provisioning Profile ID. Copy this value.

        <key>UUID</key>

<string>19000000-aaaa-bbbb-cccc-ddddeeeeffff</string>

Paste the value into your Xamarin.iOS project csproj file.  You'll need to know which build configuration it will be building on the CI server.  For me its, Ad-Hoc/iPhone

  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Ad-Hoc|iPhone' ">

    <DebugType>none</DebugType>

    <Optimize>True</Optimize>

    <OutputPath>bin\iPhone\Ad-Hoc</OutputPath>

    <ErrorReport>prompt</ErrorReport>

    <WarningLevel>4</WarningLevel>

    <ConsolePause>False</ConsolePause>

    <MtouchArch>ARMv7, ARM64</MtouchArch>

    <CodesignEntitlements>Entitlements.plist</CodesignEntitlements>

    <BuildIpa>True</BuildIpa>

    <CodesignProvision>19000000-aaaa-bbbb-cccc-ddddeeeeffff</CodesignProvision>

    <CodesignKey>iPhone Developer: Ben Rees (XABCDEFGHI)</CodesignKey>

  </PropertyGroup>

Paste the value into the CodesignProvision element.  This will force the Xamarin Builder to go looking for that exact provisioning profile.

But still no luck.  

/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets : error: No installed provisioning profiles match the installed iOS signing identities.

I also turned on some extra debugging in Bitrise and found this:

/Users/vagrant/git/iOS/Info.plist : error: Project bundle identifier 'biz.rees.CorporateBs' does not match specified provisioning profile '19000000-aaaa-bbbb-cccc-ddddeeeeffff'

AHA!  The Bundle App ID must be case sensitive!  In the Apple Developer Portal I specified it as 

biz.rees.CorporateBS

Problem solved.

Icon Design and Tooling

I have to give a shout out to Inkscape what a fantastic tool for drawing and editing vector based icons (such as SVG files).  Thoroughly recommend it.  Its free and open source!

If it isn't suitable or you're looking for a cost effective way of producing professional icons or UI design check out https://www.fiverr.com/.  Its a market place to find, connect with, and hire services of just about any kind.

While you're waiting for your designer to draw your new icons, you can hire someone to pop balloons for you, or take a bath in baked beans.

More Common Xamarin Forms Project problems

As a follow on from Resolving Common Issues Loading Xamarin Samples here are some other issues I seem to be commonly running into. These issues are not only referring to Xamarin samples, but to any Xamarin project.

Corrupt Xamarin-Android ZIP files

Another common problem seems to be with corrupt Xamarin-Android SDK zip files located here:
C:\Users\<Your Username>\AppData\Local\Xamarin\zips
You'll see an error message similar to "...zip file "C:\Users\<Your Username>\AppData\Local\Xamarin\zips\1FD832DCC1792D8ACA07FAC3259FC5A9.zip" is corrupt.

Deleting all the zip files in that folder will cause them to be downloaded again during the next build within Vs.  This will make the next build very slow for obvious reasons. Let it run its course, and resist the temptation to cancel it. It could take 20minutes or more. After they are downloaded and cached in that folder again, build speed will be back to normal.

Error "aapt.exe" exited with code -1073741819.

Another common symptom is build errors in the Android generated file Resource.cs file.
The following error will be generated if there are dashes "-" in any file in the Resource/Drawables folders.

Android SDK Updates

Generally if an error follows an Android SDK update it is most likely related to new build and SDK tools being used just installed/updated.  Like the above error the most likely symptom of this is errors from the generated file Resource.cs file in your Android project.
First try running a Clean build then a Rebuild.If that doesn't work the best bet might be to revert back to a previous version of the SDK Build tools. Also check forums.xamarin.com.

Error The "XamlCTask" task failed unexpectedly.

System.IO.FileNotFoundException: Could not load file or assembly 'Mono.Cecil, Version=0.9.6.0, Culture=neutral, PublicKeyToken=0738eb9f132ed756' or one of its dependencies. The system cannot find the file specified.
File name: 'Mono.Cecil, Version=0.9.6.0, Culture=neutral, PublicKeyToken=0738eb9f132ed756'
Resolved by Deleting the entire packages folder contents and allowing a build to restore all packages.