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Mobile Weather

A simple weather app in C++ and QML demonstrating how to talk to REST APIs with Qt

This app was developed for a CS project when I was studying. It very much fulfilled the requirements meaning you can actually search for your city and get a (more or less accurate) weather forecast for the next 5 days.

Getting Started

To build the app yourself you have to recursively clone the project to also pull in the android_openssl dependency:

$ git clone --recursive https://github.com/FMeinicke/Weather-App.git

Or, if you cloned the project regularly, don't forget to initialise the submodules:

$ git clone https://github.com/FMeinicke/Weather-App.git
$ cd Weather-App/
$ git submodule update --init

Then simply open the Weather-App.pro file in QtCreator and compile and run as usual (be sure to deploy the application to the emulator or phone before running it).

Features

  • When starting the app
    • your location will be detected via GPS (if you've given the app permission to do so) or
    • if the app is not allowed to use GPS, it tries to load the weather data for the last used location or
    • if none of the above worked, you will be prompted to search for a location yourself.
  • Searching for a specific location (because the API I used does not provide very detailed weather data for every place on earth you might need to try a bigger location near you to get an approximate forecast)
  • Weather forecast for the current and 5 days in the future
  • Switching between an overview (including the current weather state and temperatures for the day) and a detailed forecast (including humidity, wind, sunrise/sunset times, ...)
  • Saving the current location as favourite for quick access from the drawer (swipe right from the left edge of the screen to show)
  • Multi-language support (currently just English and German)

Screenshots

Issues that occurred during development and how I solved them

Missing (or not found) OpenSSL libraries on Android

Issue:

  • no way to communicate with HTTPS APIs out of the box
  • the following error occurred: 
    qt.network.ssl: QSslSocket::connectToHostEncrypted: TLS initialization failed

Solution:

  • the necessary OpenSSL libraries have to be delivered with the app (i.e. the .pro file should have a ANDROID_EXTRA_LIBS section)

  • KDAB provides those necessary libraries along with a .pri file that can be easily included into your project (https://github.com/KDAB/android_openssl):

    include(third_party/android_openssl/openssl.pri)

Wrong font on OnePlus phone

Issue:

Workaround:

  • the font has to be delivered with the app (using Qt's resource system)
  • in your main.cpp you can then load the font and set it as globale font 
    QGuiApplication app(argc, argv);
const auto id = QFontDatabase::addApplicationFont(":/fonts/Roboto/Roboto-Regular.ttf");
const auto family = QFontDatabase::applicationFontFamilies(id).at(0);
app.setFont({family, 16});

Translating dynamic strings

Issue:

  • the API returns the weather state as an English description
  • since those strings cannot be known during development they can't be translated using QtLinguist

Solution:

  • use a QMap to map the strings that I receive from the API to the translated strings (I know all of the possible strings from the API docs) 
    void CWeatherDataModel::setupWeatherStateTranslations()
{
    if (m_WeatherStateTranslations.size() != 0)
    {
        return;
    }
    m_WeatherStateTranslations["Snow"] = tr("Snow");
    m_WeatherStateTranslations["Sleet"] = tr("Sleet");
    m_WeatherStateTranslations["Hail"] = tr("Hail");
    m_WeatherStateTranslations["Thunderstorm"] = tr("Thunderstorm");
    m_WeatherStateTranslations["Heavy Rain"] = tr("Heavy Rain");
    m_WeatherStateTranslations["Light Rain"] = tr("Light Rain");
    m_WeatherStateTranslations["Showers"] = tr("Showers");
    m_WeatherStateTranslations["Heavy Cloud"] = tr("Heavy Cloud");
    m_WeatherStateTranslations["Light Cloud"] = tr("Light Cloud");
    m_WeatherStateTranslations["Clear"] = tr("Clear");
}
  • in a custom tr method the received strings from the API can be properly translated 
    QString CWeatherDataModel::weatherTr(const QString& s) const
{
    if (m_WeatherStateTranslations.contains(s))
    {
        return m_WeatherStateTranslations[s];
    }
    else
    {
        return s;
    }
}