Building Android apps on Linux

[AzuxirenLeadGuy]

Hello everyone. I am a Linux user and for a long time, I have been trying to build a mobile application on Linux with C#. In the official documentation for Uno, it is listed that it is not supported to build for android in Linux, but I have finally been successful to do so. Here are the steps I followed in my Linux machine (Ubuntu 21.10 x86_64).

1. Install the android-sdk with apt and add the environment variables to the path

# Install the android-sdk
sudo apt install android-sdk 

Next, ensure the following environment variables are initialized in the .bashrc file

export ANDROID_HOME="/usr/lib/android-sdk"
export ANDROID_SDK_ROOT="/usr/lib/android-sdk"
PATH=$PATH:$ANDROID_HOME/tools
PATH=$PATH:$ANDROID_HOME/platform-tools

For me, the files were installed in the path usr/lib/android-sdk. So it goes without saying that if the files are installed elsewhere in your machine, you'll need to edit the path accordingly.

2. Use the command-line tools to install the required packages.

Go to https://developer.android.com/studio/command-line and download the command-line tool and extract it anywhere in your machine. Then run the following:

cd cmdline-tools/bin/             # Enter the bin folder of the extracted file.

sudo ./sdkmanager --sdk_root=$ANDROID_SDK_ROOT 'cmdline-tools;latest'
# This will set up the command line tools with the $ANDROID_SDK_ROOT folder

cd $ANDROID_SDK_ROOT       # Go to the root folder of android-sdk
cd cmdline-tools/latest/bin/          # Go to the bin folder of cmdline-tools 


sudo ./sdkmanager --update                       # Update all packages currently installed
sudo ./sdkmanager 'build-tools;31.0.0'        # Install build tools for API 31
sudo ./sdkmanager 'platforms;android-31'  # Install the android-sdk platform for API 31
sudo ./sdkmanager --licenses                     # Accept all licenses

At this point, you should have all the tools required to build the apk file. You can confirm that all tools are installed correctly using

sudo ./sdkmanager --list

This will list the packages that are a) already installed, b) Yet to be installed, c) Yet to be updated

Ensure that these packages are installed:

...

Installed packages:=====================] 100% Computing updates...             
  Path                 | Version | Description                             | Location            
  -------              | ------- | -------                                 | -------             
  build-tools;29.0.3   | 29.0.3  | Android SDK Build-Tools 29.0.3          | build-tools/29.0.3  
  build-tools;31.0.0   | 31.0.0  | Android SDK Build-Tools 31              | build-tools/31.0.0  
  cmdline-tools;latest | 6.0     | Android SDK Command-line Tools (latest) | cmdline-tools/latest
  platform-tools       | 33.0.1  | Android SDK Platform-Tools              | platform-tools      
  platforms;android-31 | 1       | Android SDK Platform 31                 | platforms/android-31
  tools                | 25.0.0  | Android SDK Tools                       | tools               

Available Packages:
....

3. Configure the targetframeworks within the Mobile.csproj

Now, create a new project for Uno. I am using the unoapp-winui-net6 template

dotnet new unoapp-winui-net6 -o MyNewApp
cd MyNewApp/MyNewApp.Mobile

Now edit the MyNewApp.Mobile.csproj to have a single target framework, that is net6.0-android. In other words, change the line from

    <TargetFrameworks>net6.0-android;net6.0-ios;net6.0-maccatalyst;net6.0-macos</TargetFrameworks>

to

    <TargetFramework>net6.0-android</TargetFramework>

4. Install the workloads with dotnet

Next, install the workload for android as shown:

sudo dotnet workload install android android-33 maui-android

---

I also went ahead and ensured that the MinSdkVersion is set to 29, because of the environment I am running it in. If you need to do the same, you can edit it in the file MyNewApp.Mobile/Android/AndroidManifest.xml

Now finally, you can build by going to the MyNewApp.Mobile folder and using

dotnet build -c Release

The initial build takes a while and finally, the signed apk files are generated successfully.

Now for testing the apps, I am using waydroid to run the apps. I am able to install and run the sample template program successfully.

I hope this helps out people like me who wanted to build Android apps on Linux. Now I am no expert in android app development, so let me know if I am doing anything incorrectly.