Low performance, timer and label.

mpergand

I know by experience that to rely on a timer is all wrong.
You must rely on the system clock for good accuracy.

And that's the text update method fault's, i tried to turn off the update, and just set the last result, and it's 100% accurate.

Refresh 1000 times per sec is a heavy task, it consumes about 20% cpu on my machine and serves nothing.
Timers use the event loop and if the computer is doing heavy tasks, timers triggers might be lost.
Rely on event loops for a counter is definitely a bad idea.

Loc888

@mpergand Ok, how i can use it with Start, Stop, and Reset button? Because i am trying to move your code to another project, and work with buttons, but when i start the timer, it doesn't do anything.. Still be on 00:00:000, i run it ones, and it start from the actual minutes and seconds, then i modified your code to force it start from 0, and i broke something, now nothing is working...

Loc888

@mpergand Ok, nevermind, i am blind sometimes... I fix it.

I find the way to restart it, but i have some problems with

" time.fromString("05:00:000"); "

It's not working, how should i use that? Or how to stop the time and the timer, and re-start it again but from the last time? (I dont want to reset it when i press the stop button, and then start).

VRonin

You missed an argument and the fact that it's a static function: http://doc.qt.io/qt-5/qtime.html#fromString-1

time = QTime::fromString("05:00:000","mm:ss:zzz");

Have you considered QTimeEdit instead of QLabel?

Loc888

@VRonin Still reset when i press the start button, and when i stop and start,it starts from 0.
Comon, how to fix that? It's almost fixed.

koahnig

@Loc888 said in Low performance, timer and label.:

@VRonin Still reset when i press the start button, and when i stop and start,it starts from 0.
Comon, how to fix that? It's almost fixed.

I suggest that you are showing your actual code snippets and explain what you think they should do.

Above there are only code snippets from others, not a single snippet from you. Nobody knows what you have taken over into your code. Therefore nobody can give you sound advice.

JKSH

@Loc888 said in Low performance, timer and label.:

how to stop the time and the timer, and re-start it again but from the last time? (I dont want to reset it when i press the stop button, and then start).

The Qt timer classes don't have a built-in ability to resume timing like a stopwatch. This means you need to write extra logic to do it.

Start your QElapsedTimer. It starts counting from 0.
Call QElapsedTimer::elapsed() to find out how many milliseconds have passed since the timer was started.
When the user clicks the stop button, store the value of the elapsed time in a variable.
When the user clicks the start the button again, restart your QElapsedTimer. This makes it start from 0 again.
Add the value of the stored variable to QElapsedTimer::elapsed() to get your final stopwatch value.

@Loc888 said in Low performance, timer and label.:

Comon, how to fix that? It's almost fixed.

Since you have not shown your code at all, all the discussions in this thread is only to teach you how to use the time-related classes and functions. We cannot see how you have designed your program, so we cannot tell you how to "fix" your program.

You need to sit down and think through the logic and maths to implement the stopwatch.

Loc888

@koahnig

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QTimer>
#include <QTime>
#include <QElapsedTimer>
#include <QLabel>


int Time_Counter;

QString Temp_Time;

QTime elapsed_time_time(0,0);

QTime time(0,0);





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


    timer = new QTimer(this);

    connect(timer,SIGNAL(timeout()),this,SLOT(Time_Counter_Int()));

    
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::Show_Results()
{

    elapsed_time = QTime::fromMSecsSinceStartOfDay(time.elapsed_time());

    ui->Timer_Label->setText(elapsed_time.toString("mm:ss:zzz"));

    Temp_Time = elapsed_time.toString("mm:ss:zzz");


}

void MainWindow::on_Start_Button_clicked()
{


    time.start();

    timer->start(1);

    elapsed_time = elapsed_time.fromString(Temp_Time);

}

void MainWindow::on_Stop_Button_clicked()
{

    timer->stop();

    Temp_Time = elapsed_time.toString("mm:ss:zzz");

    elapsed_time = elapsed_time.fromString(Temp_Time,"mm:ss:zzz");


}

void MainWindow::on_Reset_Button_clicked()
{

    time.restart();

    Time_Counter = 0;
}

mrjj

Hi
You connect timer to Time_Counter_Int
but you do not seem to have such slot ??

Loc888

@mrjj Yes, i see. This is simplified version, don't care about that, i have everything in the place.
I just need to know, how to reset and stop that timer, and something to convert the value of time, to total MS, because if i just add any variable and increment it, probably it's just 80% accurate, i need to convert the time from timer to total value in MS. I am gonna try, if i can find any way to convert an QString to int value.

mrjj

@Loc888 said in Low performance, timer and label.:

find any way to convert an QString to int value.

you mean like
http://doc.qt.io/qt-5/qstring.html#toInt
`?

JKSH

@Loc888 said in Low performance, timer and label.:

I just need to know, how to reset and stop that timer

Have you tried anything at all from my last message?

mpergand

@Loc888 said in Low performance, timer and label.:

I just need to know, how to reset and stop that timer

#include <QApplication>
#include <QTimer>
#include <QElapsedTimer>
#include <QTime>
#include <QLabel>
#include <QVBoxLayout>
#include <QPushButton>

int main(int argc, char *argv[])
{

    QApplication app(argc, argv);

    int totalTime=0;
    QElapsedTimer time;
    QTimer timer;
    timer.setInterval(99);

    QWidget win;
    QLabel* timeLabel=new QLabel("00:00:000");
    QLabel* totalLabel=new QLabel("00:00:000");
    QPushButton* startButton=new QPushButton("Start");
    startButton->setCheckable(true);
    QPushButton* resetButton=new QPushButton("Reset");

    QVBoxLayout* vLayout=new QVBoxLayout;
    QHBoxLayout* hLayout=new QHBoxLayout;

    hLayout->addWidget(timeLabel);
    hLayout->addWidget(startButton);
    hLayout->addWidget(resetButton);
    vLayout->addLayout(hLayout);
    vLayout->addWidget(totalLabel);

    win.setLayout(vLayout);
    win.show();

    // timer action
    QObject::connect(&timer,&QTimer::timeout,[&time,&timeLabel](){
        QTime elapsed=QTime::fromMSecsSinceStartOfDay(time.elapsed());
        timeLabel->setText(elapsed.toString("mm:ss:zzz"));
        });

    // start/stop action
    QObject::connect(startButton,&QPushButton::toggled,[&](bool checked){

        if(checked)
            {
            time.start();
            timer.start();
            resetButton->setEnabled(false);
            startButton->setText("Stop");
            }
        else
            {
            timer.stop();
            int t=time.elapsed();
            totalTime+=t;
            QTime elapsed=QTime::fromMSecsSinceStartOfDay(totalTime);
            totalLabel->setText(elapsed.toString("mm:ss:zzz"));
            // adjust time label
            elapsed=QTime::fromMSecsSinceStartOfDay(t);
            timeLabel->setText(elapsed.toString("mm:ss:zzz"));
            resetButton->setEnabled(true);
            startButton->setText("Start");
            }

        });

    // reset action
    QObject::connect(resetButton,&QPushButton::clicked,[&timeLabel,&totalLabel,&totalTime](bool checked){
        totalTime=0;
        totalLabel->setText("00:00:000");
        timeLabel->setText("00:00:000");
        });

    return app.exec();
}

Allows multiple start/stop, cumulates each duration in totalTime.

Loc888

@mpergand Ye good one, but too much stuff to add,and it looks a little bit too complicated.
I try more than few times,and i find much much more better way. I just add:

time = elapsed.fromMSecsSinceStartOfDay(elapsed.elapsed());

Just by this one line,now when i press the start button, then stop it and restart, it still counting from the last result. Did you think about that?

Ps. When i add that line, i had some problems , because the timer doesn't want to reset the value, i fix it fast just by adding some bool variables and control some parts of code.

mpergand

Simplified to display total time only:

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    int totalTime=0;
    QElapsedTimer time;
    QTimer timer;
    timer.setInterval(99);

    QWidget win;
    QLabel* totalLabel=new QLabel("00:00:000");
    QPushButton* startButton=new QPushButton("Start");
    startButton->setCheckable(true);
    QPushButton* resetButton=new QPushButton("Reset");
    QHBoxLayout* hLayout=new QHBoxLayout;

    hLayout->addWidget(totalLabel);
    hLayout->addWidget(startButton);
    hLayout->addWidget(resetButton);

    win.setLayout(hLayout);
    win.show();

    // timer action
    QObject::connect(&timer,&QTimer::timeout,[&](){
        QTime elapsed=QTime::fromMSecsSinceStartOfDay(time.elapsed());
        elapsed=elapsed.addMSecs(totalTime);
        totalLabel->setText(elapsed.toString("mm:ss:zzz"));
        });

    // start/stop action
    QObject::connect(startButton,&QPushButton::toggled,[&](bool checked){

        if(checked)
            {
            time.start();
            timer.start();
            resetButton->setEnabled(false);
            startButton->setText("Stop");
            }
        else
            {
            timer.stop();
            totalTime+=time.elapsed();
            QTime elapsed=QTime::fromMSecsSinceStartOfDay(totalTime);
            totalLabel->setText(elapsed.toString("mm:ss:zzz"));

            resetButton->setEnabled(true);
            startButton->setText("Start");
            }
        });

    // reset action
    QObject::connect(resetButton,&QPushButton::clicked,[&totalLabel,&totalTime](bool checked){
        totalTime=0;
        totalLabel->setText("00:00:000");
        });

    return app.exec();
}