Qt SCXML Media Player Example (Static)▲

Image non disponible

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:

 
Sélectionnez
&lt;scxml
    xmlns="http://www.w3.org/2005/07/scxml"
    version="1.0"
    name="MediaPlayerStateMachine"
    initial="stopped"
    datamodel="ecmascript"
&gt;
    &lt;datamodel&gt;
        &lt;data id="media"/&gt;
    &lt;/datamodel&gt;

Compiling the State Machine▲

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

 
Sélectionnez
QT += widgets scxml

We then specify the state machine to compile:

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

The Qt SCXML Compiler, qscxmlc, is run automatically to generate statemachine.h and statemachine.cpp, and to add them to the HEADERS and SOURCES variables for compilation.

Instantiating the State Machine▲

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

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

#include &lt;QApplication&gt;

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

    MediaPlayerStateMachine machine;
    MainWindow mainWindow(&amp;machine);

Connecting to States▲

The media player state machine will send out events when users tap a control and when playback starts or stops, as specified in the SCXML file:

 
Sélectionnez
    &lt;state id="stopped"&gt;
        &lt;transition event="tap" cond="isValidMedia()" target="playing"/&gt;
    &lt;/state&gt;

    &lt;state id="playing"&gt;
        &lt;onentry&gt;
            &lt;assign location="media" expr="_event.data.media"/&gt;
            &lt;send event="playbackStarted"&gt;
                &lt;param name=