Launching a native application from Qt

This code snippet shows how to launch a native application from Qt. The example has been tested launching the Symbian camera application on the Symbian platform, but the code should work generically.

Article Metadata

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Tested with

SDK: Qt SDK

Devices(s): Nokia 5800 XpressMusic

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Compatibility

Platform(s): S60 3rd Edition, FP1, FP2
S60 5th Edition

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Article

Keywords: QProcess

Created: tepaa (29 Apr 2009)

Last edited: hamishwillee (17 Oct 2012)

Header

The ProcessHandler starts the process and listens for its states.

#include <QObject>
#include <QProcess>
 
class ProcessHandler : public QObject
    {
    Q_OBJECT
 
    public:
        ProcessHandler(QObject *parent = 0);
        ~ProcessHandler();
 
    public:
        void StartCameraApp();
 
    public Q_SLOTS:
        void stateChanged(QProcess::ProcessState state);
        void error(QProcess::ProcessError error);
 
    private:
        QProcess*   process;
    };

Source

Create QProcess and start listening for process state changes.

ProcessHandler::ProcessHandler(QObject *parent)
: QObject(parent)
    {
    process = new QProcess(this);
    QObject::connect(process, SIGNAL(stateChanged(QProcess::ProcessState)),
                     this, SLOT(stateChanged(QProcess::ProcessState)));
    }

Class descruction:

ProcessHandler::~ProcessHandler()
    {
    if (process->state() != QProcess::NotRunning)
        {
        // Close process if it is running
        process->close();
        }
    }

Start the Symbian native camera Cameraapp.exe:

void ProcessHandler::StartCameraApp()
    {
    QString program = "Cameraapp.exe";
    process->start(program);    
    }

QProcess signals the error to the error slot:

void ProcessHandler::error(QProcess::ProcessError error)
    {
    switch (error)
        {
        case QProcess::FailedToStart:
        case QProcess::Crashed:
        case QProcess::Timedout:
        case QProcess::ReadError:
        case QProcess::WriteError:
        case QProcess::UnknownError:
            {
            // TODO: Handle error
            break;
            }
        default:
            {
            break;
            }
        };
    }

QProcess signals the process state changes to the stateChanged slot.

void ProcessHandler::stateChanged(QProcess::ProcessState state)
    {
    switch (state)
        {
        case QProcess::NotRunning:
        case QProcess::Starting:
        case QProcess::Running:
            {
            // TODO: do what you want with
            // different states
            break;
            }
        default:
            {
            break;
            }
        };
    }

Postconditions

The Symbian native camera is started.