【QT问题解决】QT Modbus rtu 拖动主界面时modbus的槽函数无法响应的解决方案

问题 Modbus放在主线程，界面事件会阻塞信号传输

在使用QT5.14.2时 使用QT自带的QModbusClient类实现对一个力传感器的数据读取。本人为了测试就将modbus读取逻辑等都写在主线程中，但是本人采用modbus异步通讯的方式，给从站发一个读取数据的信号（sendReadRequest），然后使用信号槽等待从站回复数据（readSerialForceData）。这种方式的好处是不会阻塞主线程。

但是！本人发现一个问题，就是在我拖动主界面的时候，modbus通讯就停止了！当我松开鼠标的时候，modbus正常通讯！目前还不知道为什么会这样，猜测是鼠标事件影响了modbus的信号槽机制。但是我试了一下，其他的槽函数都是能正常触发的，比如定时器之类。在我拖动界面的时候，UI界面也可以正常的刷新。只有modbus被阻塞了。

void MainWindow::on_readRequest()
{// 读取寄存器QModbusDataUnit readUnit(QModbusDataUnit::HoldingRegisters,0,1);if (auto *reply = modbusDevice->sendReadRequest(readUnit, 1)){if (!reply->isFinished())connect(reply, &QModbusReply::finished, this, &MainWindow::readSerialForceData);elsedelete reply; // broadcast replies return immediately}else{//底部状态栏显示ui->statusBar->showMessage(tr("Read error: ") + modbusDevice->errorString(), 5000);}
}

void MainWindow::readSerialForceData()
{auto reply = qobject_cast<QModbusReply *>(sender());if (!reply)return;if (reply->error() == QModbusDevice::NoError){const QModbusDataUnit unit = reply->result();//遍历数据单元的值for (int i = 0, total = int(unit.valueCount()); i < total; ++i){qint16 sValue = static_cast<qint16>(unit.value(i));forceData_Temp = sValue/10.0;const QString entry = tr("Address: %1, Value: %2").arg(unit.startAddress() + i).arg(QString::number(sValue));ui->textBrowser_Log->append(entry);}}else if (reply->error() == QModbusDevice::ProtocolError){statusBar()->showMessage(tr("Read response error: %1 (Mobus exception: 0x%2)").arg(reply->errorString()).arg(reply->rawResult().exceptionCode(), -1, 16), 5000);}else{statusBar()->showMessage(tr("Read response error: %1 (code: 0x%2)").arg(reply->errorString()).arg(reply->error(), -1, 16), 5000);}reply->deleteLater();
}

解决方案 将modbus放在子线程实现

经过测试，发现将modbus放在子线程中，通过信号槽与主线程进行通讯，将数据保存成静态变量或者全局变量，即可解决问题。

这里新建一个serialThread 类用
.h文件

class serialThread : public QObject
{Q_OBJECT
public:serialThread(QObject *parent = Q_NULLPTR);~serialThread();QModbusClient *modbusDevice = nullptr;QDateTime startTime;QDateTime endTime;double intervalTime = 0;//串口数据间隔时间double intervalTime_Last=0;//数据采集定时器QTimer *pollTimer;//串口数据读取定时器signals:void sig_connectSerialFinished(bool flag);void sig_disconnectSerialFinished(bool flag);public slots:void startThread();void on_connectSerial();void on_disconnectSerial();void on_startReadData();void on_stopReadData();void on_readRequest();void on_readRequestFinished();
};#endif // SERIALTHREAD_H

.cpp文件

#include "serialthread.h"serialThread::serialThread(QObject *parent ) : QObject(parent)
{qDebug()<<"串口线程构造函数:"<<QThread::currentThreadId();
}serialThread::~serialThread()
{//退出串口if (modbusDevice){modbusDevice->disconnectDevice();}delete modbusDevice;}void serialThread::startThread()
{qDebug()<<"串口线程成员函数 startThread :"<<QThread::currentThreadId();modbusDevice = new QModbusRtuSerialMaster(this);
}void serialThread::on_connectSerial()
{qDebug()<<"串口线程成员函数 on_connectSerial :"<<QThread::currentThreadId();QMutexLocker locker(&ForceSensorGlobal::mutex);  // 锁定互斥锁//设置串口号modbusDevice->setConnectionParameter(QModbusDevice::SerialPortNameParameter,ForceSensorGlobal::SeriComName);//设置波特率modbusDevice->setConnectionParameter(QModbusDevice::SerialBaudRateParameter,ForceSensorGlobal::BaudRate);//设置数据位modbusDevice->setConnectionParameter(QModbusDevice::SerialDataBitsParameter,ForceSensorGlobal::DataBits);//设置奇偶检验switch(ForceSensorGlobal::ParityID){case 0: modbusDevice->setConnectionParameter(QModbusDevice::SerialParityParameter,QSerialPort::NoParity);break;case 1: modbusDevice->setConnectionParameter(QModbusDevice::SerialParityParameter,QSerialPort::EvenParity);break;case 2: modbusDevice->setConnectionParameter(QModbusDevice::SerialParityParameter,QSerialPort::OddParity);break;case 3: modbusDevice->setConnectionParameter(QModbusDevice::SerialParityParameter,QSerialPort::SpaceParity);break;case 4: modbusDevice->setConnectionParameter(QModbusDevice::SerialParityParameter,QSerialPort::MarkParity);break;default: break;}//设置停止位switch(ForceSensorGlobal::StopBitsID){case 0: modbusDevice->setConnectionParameter(QModbusDevice::SerialStopBitsParameter,QSerialPort::OneStop);break;case 1: modbusDevice->setConnectionParameter(QModbusDevice::SerialStopBitsParameter,QSerialPort::OneAndHalfStop);break;case 2: modbusDevice->setConnectionParameter(QModbusDevice::SerialStopBitsParameter,QSerialPort::TwoStop);break;default: break;}//设置执行请求时间modbusDevice->setTimeout(1000);//设置执行请求次数modbusDevice->setNumberOfRetries(3);//连接串口 并发送成功与否标志emit sig_connectSerialFinished(modbusDevice->connectDevice());pollTimer = new QTimer;pollTimer->setTimerType(Qt::PreciseTimer);//精确定时pollTimer->setInterval(ForceSensorGlobal::IntervalTime);connect(pollTimer,&QTimer::timeout, this, &serialThread::on_readRequest);}void serialThread::on_disconnectSerial()
{modbusDevice->disconnectDevice();emit sig_disconnectSerialFinished(true);}void serialThread::on_startReadData()
{QMutexLocker locker(&ForceSensorGlobal::mutex);  // 锁定互斥锁//清空一下数据 方便再次存储ForceSensorGlobal:: recordData.clear();QVector<double> vectorTemp;for (int i = 0; i < 2; i++){ForceSensorGlobal::recordData.append(vectorTemp);}startTime = QDateTime::currentDateTime();//获取开始时间pollTimer->setInterval(ForceSensorGlobal::IntervalTime);pollTimer->start();qDebug() <<"子线程 on_startReadData ";
}void serialThread::on_stopReadData()
{pollTimer->stop();qDebug() <<"子线程 on_stopReadData ";
}void serialThread::on_readRequest()
{// 读取寄存器QModbusDataUnit readUnit(QModbusDataUnit::HoldingRegisters,0,1);if (auto *reply = modbusDevice->sendReadRequest(readUnit, 1)){if (!reply->isFinished())connect(reply, &QModbusReply::finished, this, &serialThread::on_readRequestFinished);elsereply->deleteLater(); // broadcast replies return immediately}else{//读取错误qDebug() <<"读取错误: " <<modbusDevice->errorString();}
}void serialThread::on_readRequestFinished()
{auto reply = qobject_cast<QModbusReply *>(sender());if (!reply)return;QMutexLocker locker(&ForceSensorGlobal::mutex);  // 锁定互斥锁if (reply->error() == QModbusDevice::NoError){const QModbusDataUnit unit = reply->result();//遍历数据单元的值for (int i = 0, total = int(unit.valueCount()); i < total; ++i){//接受信号的时间endTime = QDateTime::currentDateTime();intervalTime = startTime.msecsTo(endTime) / 1000.0;double now = (intervalTime - intervalTime_Last)*1000.0;qDebug() <<now;intervalTime_Last = intervalTime;//收到的数据是uint16 需转换为int16qint16 sValue = static_cast<qint16>(unit.value(i));//传感器默认有一位小数，需除以10double forceData_Temp = sValue/10.0;//将时间 力数据存在到全局变量中ForceSensorGlobal::recordData[0].append(intervalTime);ForceSensorGlobal::recordData[1].append(forceData_Temp);}}else if (reply->error() == QModbusDevice::ProtocolError){//接收到的响应信息是协议错误qDebug() <<"接收到的响应信息是协议错误: " <<modbusDevice->errorString();}else{//接收到的响应信息是其他错误qDebug() <<"接收到的响应信息是其他错误: " <<modbusDevice->errorString();}reply->deleteLater();
}

在主线程中通过moveToThread，将modbus放入子线程

主界面.h文件

#ifndef MAINWINDOW_H
#define MAINWINDOW_H#include <QMainWindow>
#include <QSerialPort>
#include <QtSerialBus>
#include <QModbusDataUnit>
#include <QModbusClient>
#include <QSerialPortInfo>
#include <QMessageBox>
#include <QDebug>
#include <QSettings>
#include "forcesensorglobal.h"
#include "qcustomplot.h"
#include "CurvePlot.h"
#include "serialthread.h"namespace Ui {
class MainWindow;
}class MainWindow : public QMainWindow
{Q_OBJECTpublic:explicit MainWindow(QWidget *parent = nullptr);~MainWindow();/*************串口通讯线程***************///串口线程QThread * mySerialThread;//串口操作类serialThread  *mySerialModbus;/***************定时器**********************/QTimer *plotTimer;////UI界面初始化void initUI();//搜索串口void SearchSerialPorts();signals:void sig_connectSerial();void sig_disconnectSerial();void sig_startReadData();void sig_stopReadData();private slots:void on_plotTimerTimeOut();void on_pBtn_connectSerial_clicked();void on_pBtn_disconnectSerial_clicked();//接受子线程 modbus串口连接完成信号void on_connectSerialFinished(bool flag);//接受子线程 modbus串口断开完成信号void on_disconnectSerialFinished(bool flag);void on_pBtn_refreshSerial_clicked();void on_pBtn_startRead_clicked();void on_pBtn_stopRead_clicked();void on_pBtn_sendData_clicked();
private:Ui::MainWindow *ui;
};#endif // MAINWINDOW_H

主界面.cpp文件

#include "mainwindow.h"
#include "ui_mainwindow.h"MainWindow::MainWindow(QWidget *parent) :QMainWindow(parent),ui(new Ui::MainWindow)
{ui->setupUi(this);initUI();/*创建串口线程*/mySerialModbus = new serialThread();mySerialThread = new QThread;mySerialModbus->moveToThread(mySerialThread);//线程开始mySerialThread->start();connect(mySerialThread, &QThread::started, mySerialModbus, &serialThread::startThread);connect(mySerialThread, &QThread::finished, mySerialModbus, &QObject::deleteLater);//终止线程时要调用deleteLater槽函数connect(mySerialThread, &QThread::finished, mySerialModbus, &QObject::deleteLater);/*绘图刷新定时器*/plotTimer = new QTimer;plotTimer->setInterval(100);connect(plotTimer,&QTimer::timeout, this, &MainWindow::on_plotTimerTimeOut);/*****************信号槽*********************************///主线->子线程 串口连接信号connect(this, &MainWindow::sig_connectSerial, mySerialModbus, &serialThread::on_connectSerial);//主线->子线程 串口断开信号connect(this, &MainWindow::sig_disconnectSerial, mySerialModbus, &serialThread::on_disconnectSerial);//主线->子线程 开始采集信号connect(this, &MainWindow::sig_startReadData, mySerialModbus, &serialThread::on_startReadData);//主线->子线程 停止采集信号connect(this, &MainWindow::sig_stopReadData, mySerialModbus, &serialThread::on_stopReadData);//子线程->主线 串口连接完成信号connect(mySerialModbus, &serialThread::sig_connectSerialFinished,this,&MainWindow::on_connectSerialFinished);//子线程->主线 串口断开完成信号connect(mySerialModbus, &serialThread::sig_disconnectSerialFinished,this,&MainWindow::on_disconnectSerialFinished);void MainWindow::on_pBtn_connectSerial_clicked()
{//更新数据ForceSensorGlobal::SeriComName = ui->cBox_SeriComName->currentText();ForceSensorGlobal::BaudRate = ui->cBox_BaudRate->currentText().toInt();ForceSensorGlobal::DataBits = ui->cBox_DataBits->currentText().toInt();ForceSensorGlobal::ParityID = ui->cBox_Parity->currentIndex();ForceSensorGlobal::StopBitsID = ui->cBox_StopBits->currentIndex();ForceSensorGlobal::IntervalTime = ui->sBox_Interval->value();emit sig_connectSerial();qDebug()<<"主线程 sig_connectSerial :"<<QThread::currentThreadId();}void MainWindow::on_pBtn_disconnectSerial_clicked()
{on_pBtn_stopRead_clicked();emit sig_disconnectSerial();
}void MainWindow::on_connectSerialFinished(bool flag)
{if (flag){// 设置控件可否使用ui->pBtn_connectSerial->setEnabled(false);ui->pBtn_refreshSerial->setEnabled(false);ui->pBtn_disconnectSerial->setEnabled(true);}else    //打开失败提示{QMessageBox::information(this,tr("错误"),tr("连接从站失败！"),QMessageBox::Ok);}
}void MainWindow::on_disconnectSerialFinished(bool flag)
{if (flag){// 设置控件可否使用ui->pBtn_connectSerial->setEnabled(true);ui->pBtn_refreshSerial->setEnabled(true);ui->pBtn_disconnectSerial->setEnabled(false);}else{QMessageBox::information(this,tr("错误"),tr("断开连接失败！"),QMessageBox::Ok);}}void MainWindow::on_pBtn_refreshSerial_clicked()
{//填充串口号组合框SearchSerialPorts();
}void MainWindow::on_pBtn_startRead_clicked()
{ForceSensorGlobal::IntervalTime = ui->sBox_Interval->value();emit sig_startReadData();plotTimer->start();}void MainWindow::on_pBtn_stopRead_clicked()
{plotTimer->stop();emit sig_stopReadData();}}