Launching a native application from Qt

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 (11 Oct 2012)

Overview

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.

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.