My failed attempt to Debug Xamarin.Android

DebugXamarinAndroid.md

Step 1

I started with a fresh clone of xamarin-android and checked out the d15-7 branch.

Need to specify MSBUILD=msbuild if we plan on using VS for Mac:

make prepare all MSBUILD=msbuild

Otherwise, it will build with xbuild and all our IDEs use msbuild now.

Troubleshooting Step 1

Because why would it be that easy?

Java.Interop Troubles

If you have difficulty getting external/Java.Interop's prepare step to work, place the following in external/Java.Interop/bin/BuildDebug/JdkInfo.props

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <Choose>
    <When Condition=" '$(JdkJvmPath)' == '' ">
      <PropertyGroup>
        <JdkJvmPath>/Library/Java/JavaVirtualMachines/jdk1.8.0_152.jdk/Contents/Home/jre/lib/jli/libjli.dylib</JdkJvmPath>
      </PropertyGroup>
      <ItemGroup>
        <JdkIncludePath Include="/Library/Java/JavaVirtualMachines/jdk1.8.0_152.jdk/Contents/Home/include" />
        <JdkIncludePath Include="/Library/Java/JavaVirtualMachines/jdk1.8.0_152.jdk/Contents/Home/include/darwin" />
      </ItemGroup>
    </When>
  </Choose>
  <PropertyGroup>
    <JavaCPath Condition=" '$(JavaCPath)' == '' ">/Library/Java/JavaVirtualMachines/jdk1.8.0_152.jdk/Contents/Home/bin/javac</JavaCPath>
    <JarPath Condition=" '$(JarPath)' == '' ">/Library/Java/JavaVirtualMachines/jdk1.8.0_152.jdk/Contents/Home/bin/jar</JarPath>
  </PropertyGroup>
</Project>

Make sure to change these paths as needed for your system.

Mono Bundle Troubles

Make sure you also see something like this:

_DownloadBundle:
  Downloading `https://xamjenkinsartifact.azureedge.net/xamarin-android/...

Xamarin.Android's CI system caches builds of mono and a few other native libraries. They are quite time consuming to build.

If it lists a 404 error, than means the build is about to attempt to build mono. You don't want to mess with this, so check and see if a recent commit is bumping mono and/or modifying mono-runtimes.csproj. You may prefer to back up a commit or two:

#NOTE: this will clear changes in your working copy, too!
git reset --hard HEAD~1

Change the number 1 to specify how many commits you want to back up to. git pull will move back forward to the latest if you mess up.

Installed Mono Troubles

You might also see:

build-tools/scripts/RequiredPrograms.targets(35,5): warning : Please download `https://xamjenkinsartifact.azureedge.net/build-package-osx-mono/2017-12/41/MonoFramework-MDK-5.10.0.47.macos10.xamarin.universal.pkg` into `~/android-archives/MonoFramework-MDK-5.10.0.47.macos10.xamarin.universal.pkg`.
build-tools/scripts/RequiredPrograms.targets(40,5): error : Could not find required program 'mono'. Please run: installer -pkg "~/android-archives/MonoFramework-MDK-5.10.0.47.macos10.xamarin.universal.pkg" -target /

You can fix this by running:

wget https://xamjenkinsartifact.azureedge.net/build-package-osx-mono/2017-12/41/MonoFramework-MDK-5.10.0.47.macos10.xamarin.universal.pkg -P ~/android-archives/
sudo installer -pkg ~/android-archives/MonoFramework-MDK-5.10.0.47.macos10.xamarin.universal.pkg -target /

Make sure the URL and paths match the error message, and retry the build.

Step 2

I opened VS Code, and opened src/Mono.Android/Android.App/Activity.cs.

I added some nonsense method:

public int Add (int x, int y)
{
    return x + y;
}

Then built again, making sure to use MSBUILD=msbuild:

make MSBUILD=msbuild

Not passing make a target implies make all.

Step 3

I opened VS for Mac and created a blank Xamarin.Android app (latest and greatest).

I opened the csproj and modified the reference to Mono.Android.dll (Right Click | Tools | Edit File):

<Reference Include="Mono.Android">
    <HintPath>/Users/youruser/Desktop/Git/xamarin-android/bin/Debug/lib/xamarin.android/xbuild-frameworks/MonoAndroid/v8.1/Mono.Android.dll</HintPath>
</Reference>

I also made sure TargetFrameworkVersion is set to v8.1 in the csproj.

After modifying the csproj, I had to restart VS for Mac.

Step 4

I opened MainActivity.cs in my project and added this line:

int result = Add(1, 2);

I added a breakpoint and ran the project.

Step 5

MissingMethodException, now that's embarrassing.