There were a few issues in the previous post on getting setting up QT+Android:

1. Android SDK had to be downgraded to be compatible with QT (5.6)
2. QT Android apps would show a white screen if ran inside the emulator without the swiftshader flag set to gpu.
3. The entire Android Studio was downloaded.

This post revisits the previous documentation on setting up the required build tools with Android and Qt.

Setup

1. Download the Android SDK.

   You can only donwload the needed command-line tools (147MB zipped). I choose to move the extracted content to /opt

   curl -O https://dl.google.com/android/repository/sdk-tools-linux-4333796.zip
   unzip sdk-tools-linux-4333796.zip # unzips to `tool`
   su -c "mkdir /opt/android/"
   su -c "mv tool /opt/android/sdk/"
   

2. Download the Android NDK

   Direct download:

curl -O https://dl.google.com/android/repository/android-ndk-r19c-linux-x86_64.zip
unzip android-ndk-r19c-linux-x86_64.zip
su -c "mkdir /opt/android/ndk"
su -c "mv android-ndk-r19c /opt/android/ndk"

3. Download Qt (used Qt 5.12.2 at the time of this writing)

download-qt5.12.2-from-website # .run file
chmod u+x qt5.12.2.run
./qt5.12.2.run
mv-extracted-contents-to /opt/Qt/5.12.2

4. Install java prerequisites.

   If OpenSUSE system, e.g. run (with privileged access)

   zypper in java-1_8_0-openjdk java-1_8_0-openjdk-devel
   

5. Create and/or download Android images and tools

   sdkmanager --list
   sdkmanager "platform-tools" "platforms;android-25"
   # Download system image files -- it's a big file, might take a while
   sdkmanager "system-images;android-25;google_apis;x86"
   sdkmanager "emulator"
   

6. Create an android virtual device

   avdmanager create avd \
   -name "insert-device-name-here-with-quotes" \
   --path path/to/device-image \
   -k "<image-name>"
   

   where <image-name> may be e.g. "system-images;android-25;google_apis;x86" Test emulator and make sure it runs

   emulator -avd <created-device-name> -skin 540x960 # (or e.g. 1200x1920)
   

   Optional: spice up the virtual device by adding keyboard support to it

   echo "hw.keyboard=yes" >> /path/to/device-avd-directory/config.ini
   # E.g. path `~/.android/avd/mydevice.avd/config.ini`
   

7. Setup environment variables. For example,

   export ANDROID_HOME='/opt/android/android-sdk/'
   export ANDROID_SDK='/opt/android/android-sdk/'
   
   # needed for android-...-....json
   export ANDROID_SDK_ROOT='/opt/android/android-sdk/'
   
   export ANDROID_NDK='/opt/android/android-ndk-r19c/'
   export ANDROID_NDK_ROOT='/opt/android/android-ndk-r19c/'
   
   QT_ROOT='/opt/Qt5.12.2/'
   QT_VER='5.12.2'
   
   # Qt
   alias qmake64="${QT_ROOT}/${QT_VER}/gcc_64/bin/qmake"
   alias qmake_andx86="${QT_ROOT}/${QT_VER}/android_x86/bin/qmake"
   alias qmake_arm7="${QT_ROOT}/${QT_VER}/android_armv7/bin/qmake"
   alias qmlscene="${QT_ROOT}/${QT_VER}/gcc_64/bin/qmlscene"
   alias qtcreator="${QT_ROOT}/Tools/QtCreator/bin/qtcreator"
   alias qtdeploy_andx86="${QT_ROOT}/${QT_VER}/android_x86/bin/androiddeployqt"
   alias qtdeploy_armv7="${QT_ROOT}/${QT_VER}/android_armv7/bin/androiddeployqt"
   
   # Needed for running desktop builds
   export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:"${QT_ROOT}/${QT_VER}/${target_platform}/lib/"
   export QML2_IMPORT_PATH="${QT_ROOT}/${QT_VER}/${target_platform}/qml/"
   export QT_PLUGIN_PATH="${QT_ROOT}/${QT_VER}/${target_platform}/plugins/"
   export QT_QPA_PLATFORM_PLUGIN_PATH="${QT_ROOT}/${QT_VER}/${target_platform}/plugins/platforms/"
   
   # Android
   alias avdmanager="${ANDROID_SDK}/tools/bin/avdmanager"
   alias androidemulator="${ANDROID_SDK}/tools/emulator"
   alias adb="${ANDROID_HOME}/platform-tools/adb"
   
   

   Be careful about adding these to your ~/.bashrc if running a QT-based desktop environment like KDE: it may break your system when trying to login.

8. Build QT application

   Originally I tried using cmake but was greeted with a continuous influx of errors which seemed to emanate from bugs and version incompatiblities. After a few hours I gave up and settled for qmake. It is possible that all the issues are fixed in the latest versions of the toolkits, but I never revisited it.

   Latest toolkits doesn't seem to work with ant anymore and must use gradle instead.

   qmake # (armv7, x86, etc depending on target platform)
   BUILD_DIR=/some/path/for/build/directory
   make
   # will auto create directory if nonexistent
   make install INSTALL_ROOT=$BUILD_DIR
   androiddeployqt --output $BUILD_DIR \
      --input /path/to/qmake-json-output-file.json \
      --android-platform $ANDROID_API_PLATOFRM \
      --verbose \
      --gradle
   

   Look under ANDROID_NDK_ROOT/platforms for valid $ANDROID_API_PLATORM.

   E.g.

   qtdeploy_x86 --output ./build_and86/ \
      --input android-<project-name>.so-deployment-settings.json \
      --android-platform android-24 \
      --verbose \
      --gradle
   

   If running for the first time, it will download and extract gradle to ~/.gradle (but for some reason it won't explicitly tell you this)

   To push APKs to an emulator while the emulator is running, do:

   adb install -r PATH/TO/file.apk