How to launch other applications in Qt

13 Sep
2009

Article Metadata

---

Tested with

Devices(s): Nokia 5800

---

Compatibility

Platform(s): Qt

---

Article

Keywords: QDesktopServices::openUrl(), QProcess::start()

Created: savaj (10 Jun 2009)

Last edited: hamishwillee (22 Nov 2011)

Overview

This code example shows how to start other applications from within a Qt application. It demonstrates QDesktopServices::openUrl() for opening URLs in the default browser and QProcess for launching arbitrary applications.

This snippet can be self-signed.

Preconditions

• Download and install the Qt SDK

Launching web browser

The class QDesktopServices provides methods for accessing common desktop services, like browser, player, e-mail client, etc. We use QDesktopServices::openUrl(), which opens the given URL in the appropriate Web browser for the user's desktop environment, and returns true if successful; otherwise returns false. If the URL is a reference to a local file (i.e., the URL scheme is "file") then it will be opened with a suitable application instead of a Web browser. For example, you can use URL "file:///c:/data/abc.png" to open abc.png in its default application. similarly you can play audio/video.

Header required

#include <QDesktopServices>
#include <QUrl>

Source code

//openUrl is static method of class QDesktopServices, so no need to create instance of it.
//Open URL in browser
QDesktopServices::openUrl(QUrl("http://www.developer.nokia.com/Community/Discussion/forumdisplay.php?40-General-Symbian-C"));

Launching RealPlayer

QProcess is used to start external programs and to communicate with them.

Header required

#include <QDesktopServices>
#include <QUrl>

Source code

//openUrl is static method of class QDesktopServices, so no need to create instance of it.
//to open vedio file in realplayer give full path here.
QDesktopServices::openUrl(QUrl("file:///e:/Videos/Nokia 5800 XpressMusic.mp4"));

Launching Email Client

Header required

#include <QDesktopServices>
#include <QUrl>

Source code

//openUrl is static method of class QDesktopServices, so no need to create instance of it.
//Open email client.
QDesktopServices::openUrl(QUrl("mailto:ratang.gir@gmail.com?subject=Testing feedback&body=HelloFriend"));

Launching other applications

Header required

#include <QProcess>

The signal error() of QProcess is emitted when an error occurs with the process. The specified error describes the type of error that occurred.

Header file

void processError(QProcess::ProcessError err);
 
QProcess process;

Source code

QtAppLauncher::QtAppLauncher(QWidget *parent)
    : QMainWindow(parent)
{
//connect error() to slot processError() to get error, if occurs.
QObject::connect( &process, SIGNAL(error(QProcess::ProcessError)), 
                      this, SLOT(processError(QProcess::ProcessError)));
 
//pass the name of executable that you want to launch. i have installed helloworld so passed helloworld.
process.start("helloworld");
}
 
//get errors, if any
void QtAppLauncher::processError(QProcess::ProcessError err)
{
	switch(err)
	{
	case QProcess::FailedToStart:
		QMessageBox::information(0,"FailedToStart","FailedToStart");
		break;
	case QProcess::Crashed:
		QMessageBox::information(0,"Crashed","Crashed");
		break;
	case QProcess::Timedout:
		QMessageBox::information(0,"FailedToStart","FailedToStart");
		break;
	case QProcess::WriteError:
		QMessageBox::information(0,"Timedout","Timedout");
		break;
	case QProcess::ReadError:
		QMessageBox::information(0,"ReadError","ReadError");
		break;
	case QProcess::UnknownError:
		QMessageBox::information(0,"UnknownError","UnknownError");
		break;
	default:
		QMessageBox::information(0,"default","default");
		break;
	}
}

Postconditions

The code snippet is expected to launch browser, realplayer and helloworld application.

Code Example

• Download File:QtAppLauncher.zip.