Qt SCXML Media Player Example (Static) | Qt SCXML 5.7

Qt 5.7 | Qt SCXML | Qt SCXML Examples | Qt SCXML Media Player Example (Static)

Qt 5.7.1 Reference Documentation

# Qt SCXML Media Player Example (Static)

Media Player Example (Static) demonstrates how to access data from an ECMAScript data model that is compiled into a C++ class.

The UI is created using Qt Widgets.

## 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.

## Using the ECMAScript Data Model

We specify the data model as a value of the datamodel attribute of the `<scxml>` element in mediaplayer-common/mediaplayer.scxml:

      <!-- enable-qt-mode: yes -->
      <scxml
          xmlns="http://www.w3.org/2005/07/scxml"
          version="1.0"
          name="MediaPlayerStateMachine"
          initial="stopped"
          datamodel="ecmascript"
      >
          <datamodel>
              <data id="media"/>
          </datamodel>

## Compiling the State Machine

We link against the Qt SCXML module by adding the following line to the .pro file:

      QT += widgets scxml

We then specify the state machine to compile:

      STATECHARTS = ../mediaplayer-common/mediaplayer.scxml

We also tell qmake to run `qscxmlc`, which generates mediaplayer.h and mediaplayer.cpp, and adds them to the `HEADERS` and `SOURCES` variables for compilation:

      load(qscxmlc)

## Instantiating the State Machine

We instantiate the generated `MediaPlayerStateMachine` class in mediaplayer-widgets-static.cpp:

      #include "mediaplayer.h"
      #include "../mediaplayer-common/mainwindow.h"

      #include <QApplication>

      int main(int argc, char **argv)
      {
          QApplication app(argc, argv);

          MediaPlayerStateMachine machine;
          MainWindow mainWindow;

To be notified when a state machine sends out an event, we connect to the corresponding signals. The media player state machine will send out events when users tap a control and when playback starts or stops:

          QObject::connect(&mainWindow, &MainWindow::tap,
                           &machine, &MediaPlayerStateMachine::tap);
          QObject::connect(&machine, &MediaPlayerStateMachine::playbackStarted,
                           &mainWindow, &MainWindow::started);
          QObject::connect(&machine, &MediaPlayerStateMachine::playbackStopped,
                           &mainWindow, &MainWindow::stopped);

Files:

- mediaplayer-widgets-static/mediaplayer-widgets-static.cpp
- mediaplayer-widgets-static/mediaplayer-widgets-static.pro