how to automatically update GUI status

Mijaz

Problem:
When I execute the following code without a while(1) loop it works correctly but it needs push Run button for the update.
When I execute with a while(1) loop it stuck with the current input, not gets ready for the next input. The output of current input displays only in the terminal, not on GUI.

my target to achieve:
whenever I will enter input, it should update output without push the run button.
How I can insert stop pushbutton?

// program
void MainWindow::on_Run_button_clicked()
{
// while(1)
// {
QString str = ui->lineEdit->text();
qDebug()<<"Input (HEX) = " << str;
bool ok;
int iVal = str.toInt(&ok,16);
QString binnumber = str.setNum(iVal, 2);
ui->lineEdit_2->setText(binnumber);
qDebug()<<"output in binary = " << binnumber;
}
//}

J.Hilk

@Mijaz
here's one way you can do it, using the signals @jsulm pointed you to

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    connect(ui->lineEdit, &QLineEdit::textEdited, this, [=]()->void{
        QString str = ui->lineEdit->text();
        qDebug()<<"Input (HEX) = " << str;
        bool ok;
        int iVal = str.toInt(&ok,16);
        QString binnumber = str.setNum(iVal, 2);
        if(ok)
            ui->lineEdit_2->setText(binnumber);
        else
            ui->lineEdit_2->setText("Not a number");
        qDebug()<<"output in binary = " << binnumber;
    });
}

replace textEdited with editingFinished if you want to run this lambda(function) only when the user presses enter/return or the line edit looses focus

jsulm

@Mijaz

while(1)

is an endless loop! Why do you need an endless loop? How often do you actually need to iterate?
"whenever I will enter input" see:

Mijaz

@jsulm
Yes, I need an endless loop.
Because I have to introduce this characteristic into a reactive jammer GUI.

jsulm

@Mijaz
https://doc.qt.io/qt-5/qlineedit.html#editingFinished
https://doc.qt.io/qt-5/qlineedit.html#textEdited

jsulm

@Mijaz said in how to automatically update GUI status:

Yes, I need an endless loop.

No, you don't. See my other post.

Mijaz

@jsulm
Ones it entered to while(1) loop it does not take any input. How I can make it ready for the next input?

jsulm

@Mijaz Did you read my previous post?
I gave you two signals. You can use editingFinished signal and connect a slot to it where you execute the code you posted but without loop.

Do you actually know that an endless loop will never end? You're basically blocking your application forever with such a loop and it is simply not needed at all...

J.Hilk

@Mijaz
here's one way you can do it, using the signals @jsulm pointed you to

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    connect(ui->lineEdit, &QLineEdit::textEdited, this, [=]()->void{
        QString str = ui->lineEdit->text();
        qDebug()<<"Input (HEX) = " << str;
        bool ok;
        int iVal = str.toInt(&ok,16);
        QString binnumber = str.setNum(iVal, 2);
        if(ok)
            ui->lineEdit_2->setText(binnumber);
        else
            ui->lineEdit_2->setText("Not a number");
        qDebug()<<"output in binary = " << binnumber;
    });
}

replace textEdited with editingFinished if you want to run this lambda(function) only when the user presses enter/return or the line edit looses focus

Mijaz

@J-Hilk
Thank you very much. It works great.
But Run and Stop button not functioned. How we can make this function dependent on the Run and Stop. When I push Run it automatically starts to convert the input to output and when press Stop it should not accept any input further.

Mijaz

@J-Hilk
This program correctly on Desktop. When I try to deply to my SDR Board then following error occures:
1).
/usr/local/Qt-4.8.7-arm/include/QtGui/qlineedit.h:196: error: ‘void QLineEdit::textEdited(const QString&)’ is protected
void textEdited(const QString &);
^

2).
/home/ijaz/Qt_applications/update_automatically/mainwindow.cpp:11: error: within this context
connect(ui->lineEdit, &QLineEdit::textEdited, this, =->void
^

3).
/home/ijaz/Qt_applications/update_automatically/mainwindow.cpp:23: warning: lambda expressions only available with -std=c++11 or -std=gnu++11 [enabled by default]
});
^
4).
/home/ijaz/Qt_applications/update_automatically/mainwindow.cpp:23: error: no matching function for call to ‘MainWindow::connect(QLineEdit*&, void (QLineEdit::)(const QString&), MainWindow const, MainWindow::MainWindow(QWidget*)::__lambda0)’
});
^

jsulm

@Mijaz said in how to automatically update GUI status:

Qt-4.8.7-arm

Is there a reason why you use Qt4?
Also your compiler for the device does not support C++11.

J.Hilk

@Mijaz
my example uses a lambda in the connect, that is only possible in Qt5 and newer. Not in QT 4

But you should be able to move it in its own class function and connect it the old fashioned way

Mijaz

@J-Hilk
I have changed this code to the old version and it works fine. There are two cases I want to execute, cases are follows.

case 1: Working correctly.

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect(ui->lineEdit_input, SIGNAL(textEdited(QString)), this, SLOT(myFunction()));

}

void MainWindow::myFunction()
{
QString str = ui->lineEdit_input->text();
qDebug()<<"Input (HEX) = " << str;
ui->lineEdit_1->setText(str);
bool ok1;
qint64 iVal = str.toLongLong(&ok1,16);
ui->lineEdit_2->setText(QString::number(iVal));
QString binnumber = str.setNum(iVal, 2);
ui->lineEdit_3->setText(binnumber);
qDebug()<<"Convert to Int = " << QString::number(iVal);
qDebug()<<"Convert to Binary = " << binnumber;
qDebug()<<"size of string binnumber = " << binnumber.size();
}

case 2: Not working correctly,

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect(ui->lineEdit_input, SIGNAL(textEdited(QString)), this, SLOT(myFunction()));
QProcess process;
process.start("sudo devmem2 0x41210000");
process.waitForFinished(-1); // will wait forever until finished
QString stdout = process.readAllStandardOutput();
qDebug()<<"Input (HEX) = " << stdout;
QChar data[8] = { stdout[98], stdout[99], stdout[100], stdout[101], stdout[102], stdout[103], stdout[104],stdout[105]};
QString str1(data, 8);
qDebug()<<"Input (HEX) = " << str1;

}

void MainWindow::myFunction()
{
QString str = ui->lineEdit_input->setText(str1);
qDebug()<<"Input (HEX) = " << str;
ui->lineEdit_1->setText(str);
bool ok1;
qint64 iVal = str.toLongLong(&ok1,16);
ui->lineEdit_2->setText(QString::number(iVal));
QString binnumber = str.setNum(iVal, 2);
ui->lineEdit_3->setText(binnumber);
qDebug()<<"Convert to Int = " << QString::number(iVal);
qDebug()<<"Convert to Binary = " << binnumber;
qDebug()<<"size of string binnumber = " << binnumber.size();
}

"QString str1" is unkown "void MainWindow::myFunction()"

jsulm

@Mijaz said in how to automatically update GUI status:

str1

Where is it defined?
The compiler actually tells you that it does not exist at that location...

Mijaz

@jsulm

I am using Qt4 because the errors occurred while cross-compilation of Qt5 to my Board.

J.Hilk

@Mijaz yes of course, str1 is a local variable inside your constructor function. myFunction()` has no knowledge of it.

also, setText is a void function, it has no return value

jsulm

@Mijaz Keep in mind that Qt4 is reached its end of life already and is not supported anymore.

Mijaz

@jsulm
QString str1 is defined in MainWindow::MainWindow(QWidget *parent) :

jsulm

@Mijaz said in how to automatically update GUI status:

QString str1 is defined in MainWindow::MainWindow(QWidget *parent) :

as local variable which only exists inside MainWindow::MainWindow(QWidget *parent)...

Mijaz

@Mijaz
now I have defined str1 in mainwindow.h
/////////////
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
QString str1;

///////////////////////
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect(ui->lineEdit_input, SIGNAL(textEdited(QString)), this, SLOT(myFunction()));
QProcess process;
process.start("sudo devmem2 0x41210000");
process.waitForFinished(-1); // will wait forever until finished
QString stdout = process.readAllStandardOutput();
qDebug()<<"Input (HEX) = " << stdout;
QChar data[8] = { stdout[98], stdout[99], stdout[100], stdout[101], stdout[102], stdout[103], stdout[104],stdout[105]};
QString str11(data, 8);
qDebug()<<"local string = " << str11;
bool ok1;
str1= str11.toInt(&ok1,16);
qDebug()<<"Globle string = " << QString::number(str1);

}

void MainWindow::myFunction()
{
//QString str = ui->lineEdit_input->text();
QString str = str1;
qDebug()<<"Input (HEX) = " << str;
ui->lineEdit_1->setText(str);
bool ok1;
qint64 iVal = str.toLongLong(&ok1,16);
ui->lineEdit_2->setText(QString::number(iVal));
QString binnumber = str.setNum(iVal, 2);
ui->lineEdit_3->setText(binnumber);
qDebug()<<"Convert to Int = " << QString::number(iVal);
qDebug()<<"Convert to Binary = " << binnumber;
qDebug()<<"size of string binnumber = " << binnumber.size();
}
//////////////
error now:

/home/ijaz/QT_Final_project/my_push_button_update/mainwindow.cpp:22: error: no matching function for call to ‘QString::number(QString&)’
qDebug()<<"Globle string = " << QString::number(str1);
^