通过线程更新ui

Question

hi I have a problem with updating ui by a thread. code works correctly but the problem is when I want to move my window as you know in that moment ui thread will stop updating. and my thread sends values to stopped thread that causes error. I don't know how to fix this.

here is my thread code header:

#ifndef READERTHREAD_H
#define READERTHREAD_H
#include <QtSerialPort/QSerialPort>
#include <QtSerialPort/QSerialPortInfo>
#include <QThread>

class readerThread : public QThread
{
    Q_OBJECT
public:
    explicit readerThread(QObject *parent = 0);
    void run();
    bool stop = false;
    QByteArray port_input;
    QByteArray payload;
    quint8 starter_symbol = 0;
    quint8 message_length = 0;
    quint8 message_ID = 0;
    readerThread *thread;
signals:
    void updated(QByteArray , quint8);

private:
    QSerialPort *serial;

};

#endif // READERTHREAD_H

my thread .cpp:

#include "readerthread.h"
#include <QtCore>

readerThread::readerThread(QObject *parent) :
    QThread(parent)
{

    serial = new QSerialPort(this);

    foreach (const QSerialPortInfo &serialPortInfo, QSerialPortInfo::availablePorts())
    serial->setPortName(serialPortInfo.portName());

    serial->setBaudRate(QSerialPort::Baud115200);

    serial->setDataBits(QSerialPort::Data8);

    serial->setParity(QSerialPort::NoParity);

    serial->setFlowControl(QSerialPort::NoFlowControl);

    serial->setStopBits(QSerialPort::OneStop);

//    serial->setReadBufferSize(8192);

    serial->open(QIODevice::ReadOnly);

    serial->errorString();

}

void readerThread::run()
{
    while(serial->isOpen())
    {
        port_input.append(serial->readAll());
        if(port_input.count() >= 150)
        {
           starter_symbol = port_input.indexOf(254);
           if((port_input.at(starter_symbol + 3) == 01) && (port_input.at(starter_symbol + 4) == 01))
           {
              message_length = port_input.at(starter_symbol + 1);
              message_ID = port_input.at(starter_symbol + 5);
              payload = port_input.mid(starter_symbol + 6 , message_length);
              port_input.remove(starter_symbol , message_length + 8);
              emit updated(payload , message_ID);
           }
           port_input.remove(0 , starter_symbol);
        }
    }
}

and here my mainwindow.cpp in short :

   struct mavlink_attitude_t
        {
            /// <summary> Timestamp (milliseconds since system boot) </summary>
              quint32 time_boot_ms;
                /// <summary> Roll angle (rad, -pi..+pi) </summary>
              float roll;
                /// <summary> Pitch angle (rad, -pi..+pi) </summary>
              float pitch;
                /// <summary> Yaw angle (rad, -pi..+pi) </summary>
              float yaw;
                /// <summary> Roll angular speed (rad/s) </summary>
              float rollspeed;
                /// <summary> Pitch angular speed (rad/s) </summary>
              float pitchspeed;
                /// <summary> Yaw angular speed (rad/s) </summary>
              float yawspeed;

        };

    MainWindow::MainWindow(QWidget *parent) :
        QMainWindow(parent),
        ui(new Ui::MainWindow)
    {
        ui->setupUi(this);
        thread = new readerThread(this);
        connect(thread , SIGNAL(updated(QByteArray,quint8)) , this , SLOT(onUpdate(QByteArray,quint8)));
        thread->start();

    }

        void MainWindow::onUpdate(QByteArray payload , quint8 ID)
        {
               mavlink_attitude_t data;
               memcpy(&data,payload.data(),sizeof(mavlink_attitude_t));
               ui->timebootms->setText(QString::number(data.time_boot_ms));
               ui->roll->setText(QString::number(data.roll));
               ui->pitch->setText(QString::number(data.pitch));
               ui->yaw->setText(QString::number(data.yaw));
               ui->rollspeed->setText(QString::number(data.rollspeed));
               ui->pitchspeed->setText(QString::number(data.pitchspeed));
               ui->yawspeed->setText(QString::number(data.yawspeed));
        }

Answer 1

You are likely hitting this issue that we fixed a while ago for the 5.5 release:

Stopping streaming when window is resizing or moving

You can backport the change if you wish.

More importantly, it is relatively strange to use threading on your own when the library is designed to have an async API. I wrote a simple example back then that demonstrates the proper async use of the library for reading purposes. Here can you find it:

Command Line Reader Async Example