doc: WSL-Ubuntu-Android Install Guide

doc/build-android.md

@@ -22,4 +22,249 @@ This is an example command for a default build with no disabled dependencies:
 
 ## Building and packaging
 
-After the depends are built configure with one of the resulting prefixes and run `make && make apk` in `src/qt`.
+After the depends are built configure with one of the resulting prefixes and run `make && make apk` in `src/qt`.
+
+# Bitcoin Core WSL Ubuntu Android QML GUI
+
+This guide will walk you through the steps to build Bitcoin Core QML APKs using WSL Ubuntu 22.04 on Windows 11.
+
+## Prerequisites
+
+1. Install WSL Ubuntu 22.04 on Windows 11. You can find a comprehensive guide [here](https://ubuntu.com/tutorials/install-ubuntu-on-wsl2-on-windows-11-with-gui-support#1-overview).
+
+## Installation Steps
+
+### Step 1: Update WSL Ubuntu 22.04
+
+After installing Ubuntu, run the following commands to update it:
+
+```bash
+sudo apt update
+sudo apt upgrade
+```
+
+### Step 2: Install Bitcoin Core Dependencies
+
+Next, install the necessary Bitcoin Core dependencies with the following commands:
+
+```bash
+sudo apt install build-essential libtool autotools-dev automake pkg-config bsdmainutils curl git
+```
+
+Also install the QML specific dependencies:
+
+```bash
+sudo apt install qtdeclarative5-dev qtquickcontrols2-5-dev
+```
+
+### Step 3: Install Android Studio
+
+Follow the instructions below to install Android Studio and Android NDK on your system:
+
+1. Install OpenJDK-11-JDK:
+
+    ```bash
+    sudo apt install openjdk-11-jdk
+    ```
+
+2. Verify the installation by checking the java version:
+
+    ```bash
+    java --version
+    ```
+
+3. Install Android Studio using Snap:
+
+    ```bash
+    sudo snap install android-studio --classic
+    ```
+
+4. Run Android Studio:
+
+    ```bash
+    android-studio
+    ```
+
+You can also follow the full installation guide for Android Studio and Android NDK [here](https://linuxhint.com/install-android-studio-ubuntu22-04/).
+
+### Step 4: Install Android NDK
+
+To install Android NDK:
+
+1. With a project open in Android Studio, click `Tools > SDK Manager`.
+2. Click the `SDK Tools` tab.
+3. Select the `NDK (Side by side)` and `CMake` checkboxes.
+4. Click `OK`.
+5. A dialog box will tell you how much space the NDK package consumes on disk.
+6. Click `OK`.
+7. When the installation is complete, click `Finish`.
+
+You can find the full guide [here](https://developer.android.com/studio/projects/install-ndk).
+
+### Step 5: Check Android Device Architecture
+
+Before you proceed, ensure you check your Android Device's hardware architecture. Use usbip and adb for this.
+
+1. Connect your Android device to your PC and enable USB debugging in Developer Options.
+2. Once usbip is installed, list all USB devices connected to your PC by running the following command as Administrator in `cmd`:
+
+    ```bash
+    usbipd list
+    ```
+
+    If it doesn't say `SHARED` under the `STATE` collumn then run:
+    ```bash
+    usbipd bind -b <busid>
+    ```
+
+3. Note down the `BUSID` of the device you want to connect to WSL. Then run the following command, replacing `<busid>` with the `BUSID` of your device:
+
+    ```bash
+    usbipd attach --busid <busid> --wsl
+    ```
+
+4. Install adb:
+
+    ```bash
+    sudo apt install adb
+    ```
+
+5. Check the hardware architecture of your device:
+
+    ```bash
+    adb shell getprop ro.product.cpu.abi
+    ```
+
+6. Note down the architecture (arm64-v8a, armeabi-v7a, x86_64, x86).
+
+### Step 6: Install Gradle
+
+1. Download Gradle 6.6.1:
+
+    ```bash
+    VERSION=6.6.1
+    wget https://services.gradle.org/distributions/gradle-${VERSION}-bin.zip -P /tmp
+    ```
+
+2. Extract the file:
+
+    ```bash
+    sudo unzip -d /opt/gradle /tmp/gradle-${VERSION}-bin.zip
+    ```
+
+3. Set environment variables:
+
+    ```bash
+    sudo nano /etc/profile.d/gradle.sh
+    ```
+
+4. Add the following lines to the file:
+
+    ```bash
+    export GRADLE_HOME=/opt/gradle/gradle-${VERSION}
+    export PATH=${GRADLE_HOME}/bin:${PATH}
+    ```
+
+5. Change the permissions:
+
+    ```bash
+    sudo chmod +x /etc/profile.d/gradle.sh
+    ```
+
+6. Load the environment variables:
+
+    ```bash
+    source /etc/profile.d/gradle.sh
+    ```
+
+7. Verify the installation by checking the Gradle version:
+
+    ```bash
+    gradle -v
+    ```
+
+You can follow the full guide to install Gradle [here](https://linuxhint.com/installing_gradle_ubuntu/).
+
+### Step 7: Build APKs
+
+0. Before building the APKs, run the following commands:
+
+    ```bash
+    PATH=$(echo "$PATH" | sed -e 's/:\/mnt.*//g') # strip out problematic Windows %PATH% imported var
+    sudo bash -c "echo 0 > /proc/sys/fs/binfmt_misc/status" # Disable WSL support for Win32 applications.
+    ```
+
+    More details on this step can be found [here](https://github.com/bitcoin/bitcoin/blob/master/doc/build-windows.md#compiling-with-windows-subsystem-for-linux).
+
+1. Now, you need to build the dependencies for the specific Android API Level, for which you can follow the guide found at the top of this doc [here](https://github.com/bitcoin-core/gui-qml/blob/main/doc/build-android.md).
+
+    i.e. from the `depends` directory of the project run:
+
+    ```bash
+    ANDROID_SDK=/home/<username>/Android/Sdk ANDROID_NDK=/home/<username>/Android/Sdk/ndk/23.1.7779620 make HOST=aarch64-linux-android ANDROID_API_LEVEL=28 ANDROID_TOOLCHAIN_BIN=/home/<username>/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/linux-x86_64/bin
+    ```
+    if you get an error like this:
+
+    ```bash
+    global/qlogging:1296:13 n = backtrace(...
+    ```
+
+    find the file qlogging.cpp (depends/work/build/[host-platform-triplet]/qt/5.15.5-4750f35e363/qtbase/src/corelib/global/qlogging.cpp) then you need to edit the function with the following:
+
+    ```
+    static QStringList backtraceFramesForLogMessage(int frameCount)
+    {
+        QStringList result;
+        if (frameCount == 0)
+            return result;
+
+    #ifdef Q_OS_ANDROID
+        result.append(QStringLiteral("Stack trace generation not supported on Android."));
+    #else
+    // existing code here...
+    #endif
+    return result;
+    }
+    ```
+    Also make sure to add the ANDROID_HOME variable to your .bashrc file:
+
+    ```bash
+    nano ~/.bashrc
+    ```
+    then add the following line to the end of the file:
+
+    ```bash
+    export ANDROID_HOME=/home/<username>/Android/Sdk
+    export PATH=$PATH:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools
+    ```
+
+2. Once the depends are built, configure them using the newly created configure file and run it from the root directory of the project i.e.:
+
+    ```bash
+    CONFIG_SITE=$PWD/depends/aarch64-linux-android/share/config.site ./configure --with-qml --disable-bench --disable-wallet
+    ```
+
+    The above will build the binaries without the wallet and benchmarking tools. You can also build the binaries with the wallet and benchmarking tools by removing the `--disable-bench` and `--disable-wallet` flags.
+
+3. To build the APKs, run the following command from the `src/qt` directory of the project:
+
+    ```bash
+    make && make apk
+    ```
+    or to be thorough:
+
+    ```bash
+    cd src/qt
+    ```
+    ```bash
+    make
+    ```
+    ```bash
+    make apk
+    ```
+
+4. Once the APKs are built, install the debug version on your connected device using the following command from within the `src/qt` directory:
+
+    ```bash
+    adb install -r android/build/outputs/apk/debug/android-debug.apk
+    ```