I'm trying to redirect the output of QProcess live into my console.
Here is the code I'm using:
QProcess *process = new QProcess(this);
connect (process, SIGNAL(readyReadStandardOutput()), this, SLOT(processOutput()));
connect (process, SIGNAL(readyReadStandardError()), this, SLOT(processOutput()));
process->start(program);
void MainWindow::processOutput()
{
qDebug() << process->readAllStandardOutput();
}
However the above does not redirect the output stream live into my console. The processOutput() function seems to be called every time the program tries to print something but all the output seems to be buffered by QProcess and printed on my console only after the completion of the program started by QProcess. Any help would be greatly appreciated. Thanks!!
I have a MessageHandler Class which redirects all qDebug messages to an Console TabOutput in my GUI App.
MessageHandler::handleMessages(QtMsgType type, const QMessageLogContext &cntxt, const QString &msg)
{
switch(type)
{
case QtDebugMsg:
if(!m_appOutput)
{
fprintf(stderr, "Debug :: %s\n", qPrintable(msg));
}
else
{
m_appOutput->append(msg);
}
break;
}
}
In my main.cpp, I have registered my message handler class as follows:
qInstallMessageHandler(MessageHandler::handleMessages);
The m_appOutput is a QTextEdit which is present in the MainWindow where all my app output messages are printed.
Related
so I wrote a programm for my thesis in Qt and now i am supposed to turn it into a working web assembly, which wasnt a real problem except for the filedownload part. I rewrote my filedownload method from:
QString costumfile::read(QString filename){
QString fileName = QFileDialog::getOpenFileName(nullptr, filename, "", "Text Files (*.txt )");
QFile file(filename);
qDebug()<<filename<<"filename";
if(!file.open(QFile::ReadOnly |
QFile::Text))
{
qDebug() << " Could not open the file for reading";
return "";
}
QTextStream in(&file);
QString myText = in.readAll();
//qDebug() << myText;
file.close();
return myText;
}
To this:
QString costumfile::read(QString filename)
{
QMessageBox msgBox;
QString textUser="Open" + filename;
msgBox.setText(textUser);
msgBox.exec();
QString text="hallo";
qDebug()<<filename;
auto fileContentReady = [&](const QString &fileName, const QString &fileContent) {
if (fileName.isEmpty()) {
msgBox.setText("Error");
msgBox.exec();
} else {
text=fileContent;
qDebug()<<text<<"texstis";
return fileContent;
}
return fileContent;
};
QFileDialog::getOpenFileContent(".txt", fileContentReady);
}
and the problem is that the return doesnt wait for the lambda function because its asynch...
I then tried using eventloops which works fine in the Destop applikation but isnt supported in the webassembly Applikation.
So does someone have a good idea how to wait for the fileContentReady Function?
As far as I know, Qt for WebAssembly currently does not support waiting using event loops (at least Qt 6.2 does not). See Qt wiki:
"Nested event loops are not supported. Applications should not call e.g. QDialog::exec() or create a new QEventLoop object."
https://wiki.qt.io/Qt_for_WebAssembly
So you would have to modify your method to handle the asynchronous call. What I mean is that whatever you want to do with the file, you can write directly into the fileContentReady lambda you have. If this is a generic function, you can let the caller register a done callback to execute when the file is ready. Something like:
QString costumfile::read(QString filename,
const std::function<void(const QString&)>& done)
{
...
auto fileContentReady = [=](const QString &fileName, const QString &fileContent) {
if (fileName.isEmpty()) {
// Report error
} else {
text=fileContent;
qDebug()<<text<<"texstis";
done(text);
}
};
QFileDialog::getOpenFileContent(".txt", fileContentReady);
}
// When calling costumfile::read
read(filename, [=] (const QString& text) {
// Do something with `text`
});
Also, about the usage of QMessageBox exec(). This can also cause problems as it internally creates a nested event loop which is not yet supported in Qt for WebAssembly. Instead use the show() method.
auto msgBox = new QMessageBox();
msgBox->setText(textUser);
connect(msgBox, &QMessageBox::finished, &QMessageBox::deleteLater);
msgBox->show();
I'm new with Qt Creator and I'm trying to read data from a light sensor communicating by I2C. I made a class PortListener that should return data received on the console once called.
PortListener::PortListener(const QString &portName)
{
this->port = new QSerialPort();
port->setPortName(portName);
port->setBaudRate(QSerialPort::Baud9600);
port->setDataBits(QSerialPort::Data8);
port->setParity(QSerialPort::NoParity);
port->setStopBits(QSerialPort::OneStop);
port->setFlowControl(QSerialPort::NoFlowControl);
port->open(QIODevice::ReadWrite);
QByteArray readData = port->readAll();
qDebug() << "message:" << readData;
}
But the only message I have is:
QIODevice::read (QSerialPort): device not open
message: ""
I don't understand what that mean?
1.Open the serialport，then set the parameters.
PortListener::PortListener(const QString &portName)
{
this->port = new QSerialPort();
port->open(QIODevice::ReadWrite);
port->setPortName(portName);
port->setBaudRate(QSerialPort::Baud9600);
port->setDataBits(QSerialPort::Data8);
port->setParity(QSerialPort::NoParity);
port->setStopBits(QSerialPort::OneStop);
port->setFlowControl(QSerialPort::NoFlowControl);
}
2.Connect the readyRead signal to a slot, and the slot is like this.
void PortListener::readyReadSlot()
{
while (!port.atEnd()) {
QByteArray data = port.readAll();
}
}
This is much more like the QextSerialPort, the following is the code from my application.
void SpClient::start()
{
myComClient = new QextSerialPort(Setting::devCom);
if(myComClient->open(QIODevice::ReadWrite))
{
qDebug() << "open " << Setting::devCom << "as client success";
}
myComClient->setBaudRate(BAUD9600);
myComClient->setDataBits(DATA_8);
myComClient->setParity(PAR_NONE);
myComClient->setStopBits(STOP_1);
myComClient->setFlowControl(FLOW_OFF);
myComClient->setTimeout(50);
....
}
My guess is your code is failing to open the serial port, I have run into permissions issues under linux opening USB ports. You will just need to do a chmod to grant your $USER access mostly.
I am downloading an ".apk" file from a Url with Get method.
The file successfully donwload on my disk from the server.
I actually want to add a progressbar to my program. THE problem is : I can show the bytesReceived but I can't show the totalBytes of the file I am downloading (ContentLenth). How can I get it please from the server.
Here is what i get on my qDebug while downloading:
3498 of -1
799062 of -1
1923737 of -1
3037550 of -1
3200231 of 3200231
Here is my code:
void DownloadApk::LaunchDownload()
{
QNetworkProxy proxy;
proxy.setType(QNetworkProxy::HttpProxy);
proxy.setHostName("proxy");
proxy.setPort(8080);
QNetworkProxy::setApplicationProxy(proxy);
QUrl url("I put my Url here");
QNetworkRequest request(url);
_file = new QFile("C:/Users/Desktop/testdownload/downloadedFile.apk");
_file->open(QIODevice::WriteOnly);
QNetworkAccessManager *_manager= new QNetworkAccessManager;
_reply = _manager->get(request);// Manager is my QNetworkAccessManager
_file->write(_reply->readAll());
connect(_reply, SIGNAL(error(QNetworkReply::NetworkError)),
this, SLOT(error(QNetworkReply::NetworkError)));
connect(_reply, SIGNAL(downloadProgress(qint64, qint64)),
this, SLOT(updateProgress(qint64, qint64)));
connect(_reply, SIGNAL(finished()),
this, SLOT(finished()));
}
void DownloadApk::error(QNetworkReply::NetworkError err)
{qDebug() << err;
// Manage error here.
_reply->deleteLater();
}
void DownloadApk::updateProgress(qint64 read, qint64 total)
{
qDebug() << read <<"of"<<total ;
QByteArray b = _reply->readAll();
QDataStream out(_file);
out << b;
}
void DownloadApk::finished()
{
QMessageBox::information(this, tr("Complete"), tr("Successfully Downloaded"));
// Done
_reply->deleteLater();
_file->close();
// probably delete the file object too
}
I fixed the problem. Actually it was not a QT problem. This Qt code works correctly.
The probleme was from the server that wasn't sending ContentLenth on the header of the reply.
I have a QT4 application which wraps libssh2 in order to communicate with the embedded devices on the network. The following snippet is making me crazy for a while.
SSHClient ssh_client(host, 22);
try {
ssh_client.connect_to_host(USERNAME, PASSWORD);
ssh_client.receive_file(file_name, file_path);
} catch(const SSHException &excp) {
qDebug() << "test";
emit console(excp.what());
return;
}
I put breakpoints to qDebug() << "test"; and emit console(excp.what()); in debugger, however, they never get hit even though an SSHException is thrown. If i put a breakpoint to the return; statement, it stops with no problem.
The output is also strange. qDebug() << "test" does what it is supposed to do, but, emit console(excp.what()); is not emitting a signal. And when the control reaches to the return; statement, it returns, again with no problem.
Can anyone help me read the output of qprocess after write and loop until all task is done?
I have this code
wifi->write("scan\n");
wifi->closeWriteChannel();
wifi->waitForBytesWritten(100);
wifi->waitForReadyRead(100);
wifi->waitForFinished(100);
qDebug() << "read output" << wifi->readAllStandardOutput();
wifi->write("scan\n");
wifi->closeWriteChannel();
wifi->waitForBytesWritten(100);
wifi->waitForReadyRead(100);
wifi->waitForFinished(100);
qDebug() << "read output" << wifi->readAllStandardOutput();
the expected output must be
"OK"
"scan results"
but the ouput is
"OK"
""
thanks.
Your multiple waits are not useful for anything. All you care about is when the process finishes, so have a single waitForFinished call with a much longer timeout (those scans don't happen in ~100ms, a few seconds is a good minimum).
You should not be using the blocking waitForXxx methods. They trip up everyone and are a source of unending grief. Forget that they exist. Use process's signals to react to events as they happen.
Qt 5 + C++11
This is the way forward. This is why you should insist on using a modern development environment, if you can. It's less typing and easier to understand.
void MyObject::startWifi() {
auto process = new QProcess(this);
process->start("program", QStringList() << "argument");
connect(process, &QProcess::started, [process]{
process->write("scan\n");
process->closeWriteChannel();
});
connect(process, &QProcess::finished, [process]{
qDebug() << process->readAllStandardOutput();
process->deleteLater();
});
}
Qt 4
class MyObject : public QObject {
Q_OBJECT
QProcess m_wifi;
Q_SLOT void onStarted() {
m_wifi.write("scan\n");
m_wifi.closeWriteChannel();
}
Q_SLOT void onFinished() {
qDebug() << m_wifi.readAllStandardOutput();
}
public:
MyObject(QObject * parent = 0) : QObject(parent) {
connect(&m_wifi, SIGNAL(started()), SLOT(onStarted()));
connect(&m_wifi, SIGNAL(finished(int,QProcess::ExitStatus)),
SLOT(onFinished()));
}
Q_SLOT void start() {
m_wifi.start("program", QStringList() << "argument");
}
};
Then invoke the start method/slot on an instance of this object. That's all.