If I do not use connection I can properly exit.
In Pdv.h file
namespace Pdv {
...
extern QSqlDatabase db;
...
}
In LoginDialog.cpp file
QSqlDatabase Pdv::db;
...
Pdv::db= QSqlDatabase::addDatabase("QMYSQL3");
Pdv::db.setHostName(Pdv::DB_URL);
Pdv::db.setUserName(Pdv::DB_USER);
Pdv::db.setPassword(Pdv::DB_PASS);
Pdv::db.setDatabaseName(Pdv::DB_DB);
if(!Pdv::db.open()) {
...
// Checking user login/password and retrieve many variables
...
In mainwindow.cpp file
...
void MainWindow::closeEvent(QCloseEvent *event) {
...
if(Pdv::db.isOpen()) {
qDebug() << "Opened 1";
Pdv::db.close();
qDebug() << Pdv::db.lastError();
if(Pdv::db.isOpen())
qDebug() << "Opened 2";
}
Pdv::app->quit(); // or QApplication::quit();
}
I got this error in QTCreator console
Opened 1
QSqlError("", "", "")
Le programme s'est terminé subitement.
/home/cosmic/src/build-Pdv-Desktop-Debug/Pdv crashed.
A idea?
To make proper exit with usage of QSqlDatabase, you need preferably:
remove all instances of QSqlDatabase objects (because as you copy them, they will keep connection open).
As second condition, you need to use QSqlDatabe::removeDatabase() call. (also this call will make qDebug message if database is still in use occasionally - some QSqlDatabase object is left somewhere - it will help to identify a problem).
If you close and delete your MainWindow, and your program then crashes, then other parts of the program must be trying to use the MainWindow pointer even though it is destroyed.
I think the problem is the line of code Pdv::app->quit(); Try with QApplication::quit(); instead or review the code in Pdv::app->quit();.
Related
Im using this function so far:
bool MSSQL::checkSettings()
{
QString settingsFile = "someDir/setup.ini";
QString fileName(settingsFile);
QFile file(fileName);
if(QFileInfo::exists(fileName)) {
return true;
}
else {
qDebug() << "Error: No INI File Found on path:" << settingsFile;
return false;
}
}
which works fine.
However when I wish to use an online ini file which is reachable (because can be opened via browser link), then its a false, for example if i use:
QString settingsFile = "http://localhost/something/setup.ini";
which QT should be able to read, then it doesnt work...
any ideas?
I dont see where you are using QSettings at all. You are using QFile, which is representation of a local file.
To your question:
QSettings does not able to read/write setting from URL. You have to download it manually before instantiating QSettings, See QNetworkAccessManager.
Or you may try to make your own settings provider, by using: QSettings::registerFormat() static function.
PROBLEM DEFINITION: I have an external application called runSensor that communicates with a sensor. The sensor sends its data over UDP. Using the terminal, runSensor has two arguments to communicate with the sensor for data acquisition:start and stop.
Once at the terminal I call: $ runSensor start, a sample output is as follows:
[Time 07:20:11:000]: Device PoweredOn.
[Time 07:20:11:010]: x=1.231, y=-0.022, z=0.001
[Time 07:20:11:015]: x=1.235, y=-0.024, z=0.001
[Time 07:20:11:020]: x=1.241, y=-0.024, z=0.002
[Time 07:20:11:025]: x=1.258, y=-0.027, z=0.002
I need to call start and stop using a QT-UI. For that, I have a QDialog as follows:
Dialog::Dialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::Dialog)
{
ui->setupUi(this);
this->socketHandler = std::make_shared<udpHandler>();
this->runSensorStartProcess = std::make_shared<QProcess>();
this->runSensorStopProcess = std::make_shared<QProcess> ();
//--------------------------
// SIGNAL - SLOT
//--------------------------
connect(ui->startButton, SIGNAL(clicked()), this, SLOT(onStartButtonClicked()));
connect(ui->stopButton, SIGNAL(clicked()), this, SLOT(onStopButtonClicked()));
connect(this->socketHandler.get(), SIGNAL(sendUdpContent(QString)), this, SLOT(updateMessageBrowser(QString)));
connect(this->runSensorStartProcess.get(), SIGNAL(readyReadStandardError()), this, SLOT(printError()));
}
I use QProcess to call the start and stop of runSensor application. When I push the GUI's start button, data acquisition starts, but the the GUI freezes and I cann't click on the stop button.
CODE EXTRACTS: Here is how I implemented the start button click:
void Dialog::onStartButtonClicked()
{
this->runSensorStartProcess->start("start");
//this->runSensorStartProcess->waitForFinished(-1);
//--------------------------
// udp socket handler starts picking data and write it into a file
//--------------------------
if (!this->runSensorStartProcess->waitForStarted())
{
qWarning() << "Warning: Cannot start Cygwin process!";
}
}
stop button click implementation is similar:
void Dialog::onStopButtonClicked()
{
if(this->runSensorStartProcess.get() != NULL)
{
this->runSensorStartProcess->close();
}
this->runSensorStopProcess->start("stop");
if (!this->runSensorStopProcess->waitForStarted())
{
qWarning() << "Warning: Cannot stop Cygwin!";
}
}
Question:
How can I keep th GUI responsive after runSensorStartProcess starts?
How can I stop that process on demand (in fact by starting runSensorStartProcess)?
Do I need a separate thread for runSensorStartProcess?
Don't use any of the waitForXxx methods. That's all. Yes, it's that simple.
Note that for every waitForXxx method there's a signal you can attach to and thus react to the event you're looking for.
Aren't QProcess::kill and QProcess::terminate what you need?
Never. See also answer 1 and answer 2.
I'm trying to use QtDbus to communicate with interface provided by PowerManager in my system. My goal is very simple. I will be writing code which causes my system to hibernate using DBus interface.
So, I installed d-feet application to see what interfaces DBus is available on my system, and what I saw:
As we see, I have a few interfaces and methods from which I can choose something. My choice is Hibernate(), from interface org.freedesktop.PowerManagment
In this goal I prepared some extremely simple code to only understand mechanism. I of course used Qt library:
#include <QtCore/QCoreApplication>
#include <QtCore/QDebug>
#include <QtCore/QStringList>
#include <QtDBus/QtDBus>
#include <QDBusInterface>
int main(int argc, char **argv)
{
QCoreApplication app(argc, argv);
if (!QDBusConnection::sessionBus().isConnected()) {
fprintf(stderr, "Cannot connect to the D-Bus session bus.\n"
"To start it, run:\n"
"\teval `dbus-launch --auto-syntax`\n");
return 1;
}
QDBusInterface iface("org.freedesktop.PowerManagement" ,"/" , "" , QDBusConnection::sessionBus());
if(iface.isValid())
{
qDebug() << "Is good";
QDBusReply<QString> reply = iface.call("Methods" , "Hibernate");
if(reply.isValid())
{
qDebug() << "Hibernate by by " << qPrintable(reply.value());
}
qDebug() << "some error " << qPrintable(reply.error().message());
}
return 0;
}
Unfortunately I get error in my terminal:
Is good
some error Method "Methods" with signature "s" on interface "(null)" doesn't exist
So please tell me what's wrong with this code? I am sure that I forgot some arguments in function QDBusInterface::call() but what ?
When creating interface you have to specify correct interface, path, service. So that's why your iface object should be created like this:
QDBusInterface iface("org.freedesktop.PowerManagement", // from list on left
"/org/freedesktop/PowerManagement", // from first line of screenshot
"org.freedesktop.PowerManagement", // from above Methods
QDBusConnection::sessionBus());
Moreover, when calling a method you need to use it's name and arguments (if any):
iface.call("Hibernate");
And Hibernate() doesn't have an output argument, so you have to use QDBusReply<void> and you can't check for .value()
QDBusReply<void> reply = iface.call("Hibernate");
if(reply.isValid())
{
// reply.value() is not valid here
}
In following code I want to connect lambda function to QProcess::error signal:
void Updater::start() {
QProcess process;
QObject::connect(&process, &QProcess::error, [=] (QProcess::ProcessError error) {
qWarning() << "error " << error;
});
process.start("MyProgram");
process.waitForFinished();
}
But I get strange error:
error: no matching function for call to 'Updater::connect(QProcess*
[unresolved overloaded function type],
Updater::start()::)' });
What I do wrong here? The code executes inside method of class derived from QObject. The project configured to work with c++11.
I use Qt 5.3.1 on Linux x32 with gcc 4.9.2
Problem is that the QProcess has another error() method, so compiler just doesn't know which method use. If you want to deal with overloaded methods, you should use next:
QProcess process;
connect(&process, static_cast<void (QProcess::*)(QProcess::ProcessError)>
(&QProcess::error), [=](QProcess::ProcessError pError) {
qWarning() << "error " << pError;
});
process.start("MyProgram");
process.waitForFinished();
Yes, it looks ugly, but there is no another way (only old syntax?).
This special line tells compiler that you want to use void QProcess::error(QProcess::ProcessError error), so now there is no any ambiguity
More information you can find here.
For those who are using Qt 5.6 or later, the QProcess::error signal is deprecated. You can use the QProcess::errorOccurred signal instead to avoid the naming ambiguity and complicated casting.
QProcess process;
connect(&process, &QProcess::errorOccurred, [=](QProcess::ProcessError error) {
qWarning() << error;
});
process.start("MyProgram");
process.waitForFinished();
My code, which tries to emulate an R shell via C++, allows a user to send R commands over a tcp connection which are then passed to the R instance through the RInside::parseEvalQ function, during runtime. I have to be able to handle badly formatted commands. Whenever a bad command is given as an argument to parseEvalQ I catch the runtime error thrown (looking at RInside.cpp my specific error is flagged with 'PARSE_ERROR' 'status' within the parseEval(const string&, SEXP) function), what() gives a "St9exception" exception.
I have two problems, the first more pressing than the second:
1a . After an initial Parse Error any subsequent call to parseEvalQ results in another Parse Error even if the argument is valid. Is the embedded R instance being corrupted in some way by the parse error?
1b . The RInside documentation recommends using Rcpp::Evaluator::run to handle R exceptions in C++ (which I suspect are being thrown somewhere within the R instance during the call to parseEval(const string&, SEXP), before it returns the error status 'PARSE_ERROR'). I have experimented trying to use this but can find no examples on the web of how to practically use Rcpp::Evaluator::run.
2 . In my program I re-route stdout and stderr (at C++ level) to the file descriptor of my tcp connection, any error messages from the RInside instance get sent to the console, however regular output does not. I send RInside the command 'sink(stderr(), type="output")' in an effort to re-route stdout to stderr (as stderr appears to be showing up in my console) but regular output is still not shown. 'print(command)' works but i'd like a cleaner way of passing stdout straight to the console as in a normal R shell.
Any help and/or thoughts would be much appreciated. A distilled version of my code is shown below:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
using namespace std;
string request_cpp;
ostringstream oss;
int read(FILE* tcp_fd)
{
/* function to read input from FILE* into the 'request_cpp' string */
}
int write(FILE* tcp_fd, const string& response)
{
/* function to write a string to FILE* */
}
int main(int argc, char* argv[])
{
// create RInside object
RInside R(argc,argv);
//socket
int sd = socket(PF_INET, SOCK_STREAM, 0);
addr.sin_family = AF_INET;
addr.sin_port = htons(40650);
// set and accept connection on socket
inet_pton(AF_INET, "127.0.0.1", &addr.sin_addr);
bind(sd,(struct sockaddr*)&addr, sizeof(addr));
listen(sd,1);
int sd_i = accept(sd, 0, 0);
//re-route stdout and stderr to socket
close(1);
dup(sd_i);
close(2);
dup(sd_i);
// open read/write file descriptor to socket
FILE* fp = fdopen(sd_i,"r+");
// emulate R prompt
write(fp,"> ");
// (attempt to) redirect R's stdout to stderr
R.parseEvalQ("sink(stderr(),type=\"output\");");
// read from socket and pass commands to RInside
while( read(fp) )
{
try
{
// skip empty input
if(request_cpp == "")
{
write(fp, "> ");
continue;
}
else if(request_cpp == "q()")
{
break;
}
else
{
// clear string stream
oss.str("");
// wrap command in try
oss << "try(" << request_cpp << ");" << endl;
// send command
R.parseEvalQ(oss.str());
}
}
catch(exception e)
{
// print exception to console
write(fp, e.what());
}
write(fp, "> ");
}
fclose(fp);
close(sd_i);
exit(0);
}
I missed this weeks ago as you didn't use the 'r' tag.
Seems like you are re-implementing Simon's trusted rserver. Why not use that directly?
Otherwise, for Rcpp question, consider asking on our rcpp-devel list.