For generic skin emulator with default apis (without google apis):

List All System Images Available for Download: sdkmanager --list | grep system-images

Download Image: sdkmanager --install "system-images;android-29;default;x86"

Create Emulator: echo "no" | avdmanager --verbose create avd --force --name "generic_10" --package "system-images;android-29;default;x86" --tag "default" --abi "x86"

I recommend adding these lines to: ~/.android/avd/generic_10.avd/config.ini

skin.name=1080x1920        # proper screen size for emulator
hw.lcd.density=480
hw.keyboard=yes            # enables keys from your laptop to be sent to the emulator

If you cannot do this, you can still pass -skin 1080x1920 as an argument when starting the emulator. 
Run Emulator: emulator @generic_10 &

to resize tmp to 8G

sudo mount -o remount,size=8G,noatime /tmp;

• requires maven, ant, java8, gradle6.2, android sdk in path
• sh build.sh

Welcome to Bitcoin Wallet, a standalone Bitcoin payment app for your Android device!

This project contains several sub-projects:

• wallet: The Android app itself. This is probably what you're searching for.
• market: App description and promo material for the Google Play app store.
• integration-android: A tiny library for integrating Bitcoin payments into your own Android app (e.g. donations, in-app purchases).
• sample-integration-android: A minimal example app to demonstrate integration of Bitcoin payments into your Android app.

You'll need git, a Java 8 SDK (or later) and Gradle 4.4 (or later) for this. We'll assume Ubuntu 18.04 LTS (Bionic Beaver) for the package installs, which comes with OpenJDK 8 and Gradle 4.4.1 out of the box.

# first time only
sudo apt install git gradle openjdk-8-jdk

Create a directory for the Android SDK (e.g. android-sdk) and point the ANDROID_HOME variable to it.

Download the Android SDK Tools and unpack it to $ANDROID_HOME/.

Finally, the last preparative step is acquiring the source code. Again in your workspace, use:

# first time only
git clone -b master https://github.com/bitcoin-wallet/bitcoin-wallet.git bitcoin-wallet
cd bitcoin-wallet

You can build all sub-projects in all flavors at once using Gradle:

# each time
gradle clean build

For details about building the wallet see the specific README.

You can install the app from the app store of your choice:

• Testnet: F-Droid | Google Play
• Mainnet: F-Droid | Google Play