Update a Qt SLOT

jsulm

So, you already have a slot connected to a spinbox signal (I guess valueChanged(int i)), right?
Then in this slot you can assign the new value which is passed to the slot to a variable in your class which you then can use anywhere in your class:

void MyClass::spinboxChanged(int newValue)
{
    value = newValue;
}

For searial port see http://doc.qt.io/qt-5/qserialport.html

Rajni

ThankYou Jsulm, for your quick reply.

I am doing the same as you suggested but it doesn't work.
At run time when i am changing the value of spinbox it will not showing any changes in value .```
as shown below in code flag is a variable where i want to store the value of qspinbox and switch that value in function fuelbar() to show some images.

//your code here

#include "widget.h"
#include "ui_widget.h"
#include<QtTest/QTest>
#include<QDebug>
#include<QSerialPortInfo>

int flag ;

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
   ui->setupUi(this);

   connect(ui->FuelspinBox, SIGNAL(valueChanged(int)),this, SLOT(on_FuelspinBox_valueChanged(int)));
fuelbar();
}
void Widget:: fuelbar()
{
       ui->bar2->setVisible(false);
    ui->bar3->setVisible(false);
    ui->bar4->setVisible(false);
    ui->bar5->setVisible(false);
    ui->bar6->setVisible(false);
    ui->bar7->setVisible(false);
    ui->bar8->setVisible(false);
    ui->bar9->setVisible(false);
    ui->bar10->setVisible(false);
   // qDebug()<<"flag in fuelbar"<<flag;
    switch (flag)
    {

    case 0:

        ui->bar1->setVisible(true);
        ui->led->setVisible(true);
        ui->FuelIcon->setVisible(true);
       // lit=false;
        timer1s->start(1000);
        connect(timer1s,SIGNAL(timeout()),this,SLOT(barOFF()));
        break;

    case 1:
        ui->bar1->setVisible(true);
        ui->bar2->setVisible(true);
        ui->led->setVisible(false);
         ui->FuelIcon->setVisible(true);
        timer1s->start(1000);
        connect(timer1s,SIGNAL(timeout()),this,SLOT(bar2OFF()));
        break;

    case 2:
        ui->bar1->setVisible(true);
        ui->bar2->setVisible(true);
        ui->bar3->setVisible(true);
        ui->led->setVisible(false);

        break;

    case 3:
        ui->bar1->setVisible(true);
        ui->bar2->setVisible(true);
        ui->bar3->setVisible(true);
        ui->bar4->setVisible(true);
        ui->led->setVisible(false);
        break;

    case 4:
        ui->bar1->setVisible(true);
        ui->bar2->setVisible(true);
        ui->bar3->setVisible(true);
        ui->bar4->setVisible(true);
        ui->bar5->setVisible(true);
        ui->led->setVisible(false);
        break;

    case 5:
        ui->bar1->setVisible(true);
        ui->bar2->setVisible(true);
        ui->bar3->setVisible(true);
        ui->bar4->setVisible(true);
        ui->bar5->setVisible(true);
        ui->bar6->setVisible(true);
        ui->led->setVisible(false);
        break;

    case 6:
        ui->bar1->setVisible(true);
        ui->bar2->setVisible(true);
        ui->bar3->setVisible(true);
        ui->bar4->setVisible(true);
        ui->bar5->setVisible(true);
        ui->bar6->setVisible(true);
        ui->bar7->setVisible(true);
        ui->led->setVisible(false);
        break;

    case 7:
        ui->bar1->setVisible(true);
        ui->bar2->setVisible(true);
        ui->bar3->setVisible(true);
        ui->bar4->setVisible(true);
        ui->bar5->setVisible(true);
        ui->bar6->setVisible(true);
        ui->bar7->setVisible(true);
        ui->bar8->setVisible(true);
        ui->led->setVisible(false);
        break;

    case 8:
        ui->bar1->setVisible(true);
        ui->bar2->setVisible(true);
        ui->bar3->setVisible(true);
        ui->bar4->setVisible(true);
        ui->bar5->setVisible(true);
        ui->bar6->setVisible(true);
        ui->bar7->setVisible(true);
        ui->bar8->setVisible(true);
        ui->bar9->setVisible(true);
        ui->led->setVisible(false);
        break;

    case 9:
        ui->bar1->setVisible(true);
        ui->bar2->setVisible(true);
        ui->bar3->setVisible(true);
        ui->bar4->setVisible(true);
        ui->bar5->setVisible(true);
        ui->bar6->setVisible(true);
        ui->bar7->setVisible(true);
        ui->bar8->setVisible(true);
        ui->bar9->setVisible(true);
        ui->bar10->setVisible(true);
        ui->led->setVisible(false);
      break;
    }
}

void Widget::on_FuelspinBox_valueChanged(int arg1)
{
   flag=arg1;
  // flag=ui->FuelspinBox->value();
   qDebug()<<"flag"<<flag;
   update();
}

jsulm

Make sure your connect was successful:

qDebug() << connect(ui->FuelspinBox, SIGNAL(valueChanged(int)),this, SLOT(on_FuelspinBox_valueChanged(int)));

this should print true.

Is on_FuelspinBox_valueChanged(int) declared as slot?
Another thing to check: in on_FuelspinBox_valueChanged(int) you do not call fuelbar()! So a new flag value will not change anything! You have to call fuelbar() in on_FuelspinBox_valueChanged(int).
Does

qDebug()<<"flag"<<flag;

print something? You can place a break point there to see whether it is called.

jsulm

One more thing: your flag is not initialized! It could contain any number. You should assign it a value. And it would be better to put it in your Widget class as private property and initialize it in constructor.

Rajni

Thanks again Jsulm ..:)

yes I have put on_FuelspinBox_valueChanged(int) in SLOT.

when I call fuelbar() in on_FuelspinBox_valueChanged(int) flag value changes and it shows the respective images but in case when flag value is 0 and 1 where i have to toggle image and i am using 1 sec timer for that is misbehaving it blinks for all the cases.

Rajni

and I have to transmit that updated value of flag in serial port so do i have also write on on_FuelspinBox_valueChanged(int) .

Rajni

please help me......

jsulm

What do you mean by "that is misbehaving it blinks for all the cases"?
One thing I see is: you connect the timeout() signal each time case 0 or 1 is executed!
You should do it once (preferably in the constructor).
What does barOFF() do?

Rajni

I want to to toggle the image if flag is 0 and 1, but if i am calling fuelbar() in on_FuelspinBox_valueChanged(int) then the both image are toggling for all the case either the flag is value is 2 to 9.I have include the code below may be this will help you to understand .

Please give me some solution how can i handle it.
Thankyou..:)

void Widget:: barOFF()
{

 ui->bar1->setVisible(false);
 ui->led->setVisible(false);
  ui->FuelIcon->setVisible(false);
 timer1s->stop();
 QTest::qWait(500);
 timer1s->start(500);
 connect(timer1s,SIGNAL(timeout()),this,SLOT(barON()));

}

void Widget:: barON()
{
;
ui->bar1->setVisible(true);
ui->led->setVisible(true);
ui->FuelIcon->setVisible(true);
timer1s->stop();
QTest::qWait(500);
timer1s->start(500);
connect(timer1s,SIGNAL(timeout()),this,SLOT(barOFF()));

}
void Widget:: bar2OFF()
{
ui->bar1->setVisible(false);
ui->bar2->setVisible(false);
ui->led->setVisible(false);
ui->FuelIcon->setVisible(false);
timer1s->stop();
QTest::qWait(500);
timer1s->start(500);
connect(timer1s,SIGNAL(timeout()),this,SLOT(bar2ON()));

}

void Widget:: bar2ON()
{
ui->bar1->setVisible(true);
ui->bar2->setVisible(true);
ui->led->setVisible(false);
ui->FuelIcon->setVisible(true);
timer1s->stop();
QTest::qWait(500);
timer1s->start(500);
connect(timer1s,SIGNAL(timeout()),this,SLOT(bar2OFF()));

}

euchkatzl

as @jsulm said :

put these lines :

connect(timer1s,SIGNAL(timeout()),this,SLOT(bar2OFF()));
connect(timer1s,SIGNAL(timeout()),this,SLOT(barON()));

in your constructor because you should do that only once !!! When you call connect multiple times then your slot get called as often as your code executes the lines above !

For your approach is ist better not to use a single Timer because you have to call different slots !

Take a look at QTimer single shot function ! That ist a static function so you dont need a QTimer object :
http://doc.qt.io/qt-5/qtimer.html#singleShot

as a example for your code

void Widget:: barOFF()
{

 ui->bar1->setVisible(false);
 ui->led->setVisible(false);
  ui->FuelIcon->setVisible(false);
// timer1s->stop(); --> not needed anymore
 QTest::qWait(500);
// timer1s->start(500);
 //connect(timer1s,SIGNAL(timeout()),this,SLOT(barON()));
QTimer::singleShot(500,this,SLOT(barON()));
}

SGaist

Hi,

Important side note: Don't ever use QTest in production code. Like the name of the module suggests, it's only to be used for writing unit tests.