An application with a responsive UI showing lightning strikes on a map in real-time by combining Qt Quick, Qt Location, Qt Positioning and Qt Websockets.
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Lightning Viewer is an application that receives simulated lightning strike data from a WebSocket and displays it on a map in real-time. It features a responsive UI that adapts well to mobile, tablet and desktop-sized screens in both landscape and portrait orientation. Lightning strikes appear as icons on the map, and a separate overlay shows the distance and time of the last strike. These data layers can be hidden and revealed with toggles that are accessed by pressing the map layers button. There is also a switch for switching between map types and a button that centers the map at the user's location.
This application follows the Model-View-Controller (MVC) pattern. The
LightningItemModel
class serves as the model. It stores a list of
LightningItemData
objects and provides methods to insert new data and to get information about the latest strikes. The View is defined in multiple QML components that display the data and user interface and handle user interaction. The
Controller
class manages the data flow between the
LightningItemModel
and the QML components. The
LightningProvider
class opens a
WebSocket
connection to an online server from which it receives a JSON message for each simulated lightning strike. It parses the messages and passes the data on to the
LightningItemModel
via a signal connected to a slot in the
Controller
:
connect(m_provider.get(), &LightningProvider::dataReady, this, &Controller::onDataReceived);
Each lightning strike is represented by a
LightningItemData
struct. It contains the timestamp, latitude and longitude of the strike, and includes methods returning its distance and direction from the user location provided as a
QGeoCoordinate
。
LastStrikeInfo
struct holds information about the last lightning strike.
LightningView.qml
serves as the main view of the application. It is responsible for displaying the map and lightning data through the component
MapView.qml
, and the user controls through the component
ActionsLayer.qml
.
MapView.qml
handles map zooming and panning. It uses a
PositionSource
to obtain the user’s current location and a
Map
to display the map. Furthermore, it includes a
LightningMapLayer.qml
for displaying the lightning data and a
DistanceTimeLayer.qml
for showing information about the last lightning strike.
ActionsLayer.qml
provides a button for recentering the map and a custom switch control,
SwitchMap.qml
, for switching between different map types. It also includes a map layers button that reveals the map layer toggles. These toggles are defined in
MapLayersItem.qml
. In landscape orientation they appear next to the map layers button, while in horizontal orientation they are placed in a
Drawer
defined in
MapLayersDrawer.qml
.
The application receives simulated lightning strike data from a server maintained by Qt. The server provides a WebSocket API accepting connections on the following URL:
wss://ewea0y4bn0.execute-api.eu-north-1.amazonaws.com/production/
After connecting to the server, the application triggers the live data feed by sending the following JSON message to the server:
"{\"action\": \"simulatelightningdata\"}"