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Plasma Mobile application development

Getting involved with Plasma Mobile application environment is a perfect opportunity to familiarize with a set of important technologies:

Qt, the cross-platform application framework for creating applications that run on various software and hardware platforms with little or no change in the underlying codebase
QML, the UI specification and programming language that allows designers and developers to create applications with fluid transitions and effects, which are quite popular in mobile devices. QML is a declarative language offering a highly readable, declarative, JSON-like syntax with support for imperative JavaScript expressions.
Qt Quick, the standard library of types and functionality for QML. It includes, among many others, visual types, interactive types, animations, models and views. A QML application developer can get access this functionality with a single import statement.
CMake, the cross-platform set of tools designed to build, test and package software, using a compiler-independent method.
Kirigami, a set of QtQuick components, facilitating the easy creation of applications that look and feel great on mobile as well as on desktop devices, following the Kirigami Human Interface Guidelines.

Documentation resources

In this section you will find a set of technical resources that will accompany you during your journey as a Plasma Mobile developer. If you are just starting out with Qt, QML and CMake, you will find here enough detail so as to feel comfortable with the technologies related to Plasma Mobile development. If you are an experienced Qt developer, you can find here valuable resources so as to comply with best practices.

QtQuick and QML

Kirigami

CMake

Using the Kirigami application template

We will use the KDE flatpak SDK to develop and package the app, so all that is required is a working flatpak and flatpak-builder installation.

On Debian and derivates, you can use sudo apt install flatpak flatpak-builder.

First, clone the app template: git clone https://gitlab.com/jbbgameich/plasma-mobile-app-template.git

This repository can be used as a template to develop Plasma Mobile applications. It already includes templates for the qml ui, a c++ part, app metadata and flatpak packaging.

Local building and testing using the SDK

flatpak install flathub org.kde.Sdk//5.11 # Only needs to be done once
flatpak-builder flatpak-build-desktop --force-clean --ccache *.json
flatpak-builder --run flatpak-build-desktop *.json hellokirigami

Creating a flatpak for the phone

This assumes your system is already set up as described here. Make sure your system also supports qemu user emulation. If not, you can find help for example here

flatpak install flathub org.kde.Sdk/arm/5.11 # Only needs to be done once
flatpak-builder flatpak-build-phone --repo=arm-phone --arch=arm --force-clean --ccache *.json
flatpak build-bundle arm-phone app.flatpak org.kde.hellokirigami

Now your app is exported into app.flatpak. You can copy the file to the phone using scp:

scp app.flatpak [email protected]:/home/phablet/app.flatpak

ssh [email protected]
flatpak install app.flatpak

Your new application should now appear on the homescreen.

Using the template to develop your application

Edit the files to fit your naming and needs. In each command, replace “io.you.newapp” and “newapp” with the id and name you want to use

find . -name "CMakeLists.txt" -or -name "*.desktop" -or -name "*.xml" -or -name "*.json" -exec sed -i 's/org.kde.hellokirigami/io.you.newapp/g;s/hellokirigami/newapp/g' {} \;

for file in $(find . -name "org.kde.hellokirigami*"); do mv $file $(echo $file | sed "s/org.kde.hellokirigami/io.you.newapp/g"); done

Submitting your new application to the repository

Once your application is working and is usable, you can submit a patch to include it into the KDE flatpak repository.

After setting up git with the recommended KDE settings, you can create a new file io.you.newapp.remoteapp in the flatpak-kde-applications repository.

git clone kde:flatpak-kde-applications && cd flatpak-kde-applications

Paste the following content into the file:

ID=io.you.newapp
JSON=io.you.newapp.json
GITURL=https://gitlab.com/you/newapp.git

You can now submit the patch on Phabricator. Once accepted, your app will be automatically built, published and made available in Discover (if the KDE flatpak repository is enabled on the device).