Log File Position Source (C++)#

Logfile Position Source shows how to create and work with a custom position source. It can be useful for simulating GPS data, or when the data is received in some custom format.

Running the Example#

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

Creating custom Position Source#

In this example, the data is read from a text file, simplelog.txt. The file specifies position data using a simple text format: it contains one position update per line, where each line contains a date/time, a latitude and a longitude, separated by spaces. The date/time is in ISO 8601 format and the latitude and longitude are in degrees decimal format. Here is an excerpt from simplelog.txt:

2009-08-24T22:25:01 -27.576082 153.092415
2009-08-24T22:25:02 -27.576223 153.092530
2009-08-24T22:25:03 -27.576364 153.092648

We create a custom LogFilePositionSource class, which derives from QGeoPositionInfoSource . It reads position data from the file and distributes it via the positionUpdated() signal.

The resulting time and position information is then displayed on the screen as simple text in date/time and latitude/longitude format.

Here is the definition of the LogFilePositionSource class:

The main methods overrided by the subclass are:

  • startUpdates() : called by client applications to start regular position updates.

  • stopUpdates() : called by client applications to stop regular position updates.

  • requestUpdate() : called by client applications to request a single update, with a specified timeout.

When a position update is available, the subclass emits the positionUpdated() signal.

Here are the key methods in the class implementation:

Example project @ code.qt.io