[Solved] How to control QTimer and lineEdit

Swinetha

In my application I am reading the data from QProcess. And I am doing that splitting that data and displayed in line edit with some time delay using QTimer.

But I am unable to stop the timer when Qprocess stoped

Here is my code.
Here I am starting the QProcess
@
void Hmi1::on_start_AV_clicked()
{
QString program;
QStringList arguments;
program = "/home/IFSS/programs/VME/test";

process =new QProcess();
process->setReadChannel(QProcess::StandardOutput);
process->start(program,arguments);
connect(process,SIGNAL(readyReadStandardOutput()),this,SLOT(read_AV()));

}
@
read_AV() slot and in this slot I am starting the timer
@
void Hmi1::read_AV()
{
QByteArray b1;
QStringList strLines;

b1= process->readAllStandardOutput();

qDebug()<<QString::number(b1.length());
strLines = QString(b1).split("\n");
foreach (line_array1[a++], strLines) {; }

timer = new QTimer(this);
timer->setSingleShot(false);
connect(timer, SIGNAL(timeout()), this, SLOT(updateText()));
timer->start(1000);
@

timer slot is below

@
void Hmi1::updateText()
{
emit out(line_array1); //custom signal
connect(this,SIGNAL(out(QString *)),this,SLOT(disp(QString *)));
}
@

displaying in QLine edit

@
void Hmi1::disp(QString *line_array1)
{
ui4->lineEdit_AIV1->setText(line_array1[k++]);
ui4->lineEdit_AIV11->setText(line_array1[k++]);

    ui4->lineEdit_AIV2->setText(line_array1[k++]);
    ui4->lineEdit_AIV22->setText(line_array1[k++]);

    ui4->lineEdit_AIV3->setText(line_array1[k++]);
    ui4->lineEdit_AIV33->setText(line_array1[k++]);

    ui4->lineEdit_AIV4->setText(line_array1[k++]);
    ui4->lineEdit_AIV44->setText(line_array1[k++]);

}
@

My problemwas, if I stop the QProcess and disconnected the read_AV slot even it is displaying the text in lineEdit

but I want to develop an application like

If I click the stop button it will stop the Qprocess and stop the timer also and In LineEdit I want to display last values constantantly.

Is der any thing mis in my logic please guide me

raven-worx

the problem is in your read_AV() slot. You create on every call a new timer and overwrite the pointer to it. Thus at the end you have multiple timers triggering your updateText() slot.

Swinetha

so how can i overcome this problem?

sir I changed my code as shown below,

@
void Hmi1::on_start_AV_clicked()
{
QString program;
QStringList arguments;
program = "/home/IFSS/programs/VME/test";
timer = new QTimer(this);
process =new QProcess();
process->setReadChannel(QProcess::StandardOutput);
process->start(program,arguments);
connect(process,SIGNAL(readyReadStandardOutput()),this,SLOT(read_AV()));
}

@
is this correct way or not??

If I modify like this I am not able to connect the SLOT(updateText());

How can I change this code to requird way?
please
help me

andre

Create a single timer instance once, and re-use that. Your constructor would be a good candidate for a location to do that.

Swinetha

I am implemented the code as said by Andre,
even though it is not displayed the data

Swinetha

or is there any other concept like creating new timer every time and close that timer? is it correct or not

Jeroentjehome

Hi,
In your constructor HMI1 allocate the QProcess and the QTimer, don't start them!! but only connect the signals you need if wanted. Then in the Av_start simple start the QProcess and the QTimer.
Both the QProcess and the QTimer variables should be private members of your HMI1 class! That will fix a lot of issues here.
So, quick code example:
@
void HMI1::HMI1(QObject * parent)
: QObject(parent)
{
m_Timer = new QTimer(1000);
connect(timer, SIGNAL(timeout()), this, SLOT(updateText()));

m_Process = new QProcess();
process->setReadChannel(QProcess::StandardOutput);
process->start(program,arguments);
connect(process,SIGNAL(readyReadStandardOutput()),this,SLOT(read_AV()));
}
and:
void HMI1::read_AV()
{
if (m_Timer != NULL)
m_Timer.start();
... // do the rest here
}
@

raven-worx

it is still unclear what you actually want to achieve.
I guess you want to display every line your QProcess' std. And each line you display has to be visible for at least 1 sec.
Am i correct?

Swinetha

to raven-worx,

ya I want to display the data for every sec and also if I click stop button QProcess and timer both should stop thier process as well as timer

raven-worx

When the readyReadStandardOutput() signal is triggered it' may be that there are more/less than 1 new line available. Thus you probably wont display all the data. And it's definitely triggered more than every 1 sec.

Why don't you use a QTextEdit and append the text there?

If you have to stick to the QLineEdit (can just display single lines) you should write the stdout to a buffer, and read new lines when the timer (single instance) triggers.
(Actually the QProcess itself is already a buffer though)

Swinetha

To Jeroentje@ho..
I tried as you said even though timer will not connect to that SLOT()

Swinetha

acording to my application I should use only lineEdit to display the data

and I did nt understand

bq. If you have to stick to the QLineEdit (can just display single lines) you should write the stdout to a buffer, and read new lines when the timer (single instance) triggers.

can you explain me

raven-worx

here you go:
@
void Hmi1::on_start_AV_clicked()
{
QString program;
QStringList arguments;
program = "/home/IFSS/programs/VME/test";
process =new QProcess();
process->setReadChannel(QProcess::StandardOutput);
process->start(program,arguments);

    timer = new QTimer(this);
    timer->setInterval (1000);
    timer->setSingleShot (false);
    connect(timer, SIGNAL(timeout()), this, SLOT(read_AV()));
    timer->start();
}

void Hmi1::read_AV()
{
char buf[1024];
qint64 lineLength = process->readLine(buf, sizeof(buf));
if (lineLength > 0)
{
//set buf to your lineedit
}
}
@

As i said, with your QLineEdit you can only display a single line of data. Unless you remove all linebreaks and display the whole data in one line.
Q(Plain)TextEdit would be more appropriate for this.

Swinetha

thanks for your reply,,

I got one solution for this but once you check this one and said me is correct method or not?

code is as shown below

@
Hmi1::Hmi1(QWidget *parent) :
QWidget(parent),
ui4(new Ui::Hmi1)
{
ui4->setupUi(this);

timer=new QTimer();

}@

start_button clicked
@
void Hmi1::on_start_AV_clicked()
{
QString program;
QStringList arguments;
process =new QProcess();
process->setReadChannel(QProcess::StandardOutput);
program = "/home/IFSS/programs/VME/test";
arguments<<"1";
process->start(program,arguments);
connect(process,SIGNAL(readyReadStandardOutput()),this,SLOT(read_AV()));
}
@
read_AV() slot
@
void Hmi1::read_AV()
{
QByteArray b1;
QStringList strLines;

b1= process->readAllStandardOutput();
b1_size=b1_size+b1.length();
qDebug()<<QString::number(q++)<<" "<<QString::number(b1_size);
strLines = QString(b1).split("\n");
foreach (line_array1[a++], strLines)   {; }

if(timer!=NULL)
{
emit out(line_array1);
timer->start(1000);

      connect(this,SIGNAL(out(QString *)),this,SLOT(disp(QString *)));
    }

}
@
disp() slot
@
void Hmi1::disp(QString *line_array1)
{
ui4->lineEdit_AIV1->setText(line_array1[k++]);
ui4->lineEdit_AIV11->setText(line_array1[k++]);

    ui4->lineEdit_AIV2->setText(line_array1[k++]);
    ui4->lineEdit_AIV22->setText(line_array1[k++]);

    ui4->lineEdit_AIV3->setText(line_array1[k++]);
    ui4->lineEdit_AIV33->setText(line_array1[k++]);

    ui4->lineEdit_AIV4->setText(line_array1[k++]);
    ui4->lineEdit_AIV44->setText(line_array1[k++]);

}
@
& STOP button
@
void Hmi1::on_stop_AV_clicked()
{
if(timer->isActive())
{
connect(timer, SIGNAL(timeout()), this, SLOT(updateText()));
}
int n=process->pid();
QStringList arg;
arg<<QString::number(n);
QProcess *sh1=new QProcess();
sh1->start("kill",arg);

process->closeReadChannel(QProcess::StandardOutput);
process->close();

}
@

@
void Hmi1::updateText()
{
timer->stop();
}
@

by using this I am able to control the timer and Process