Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
  • Search
  • Get Qt Extensions
  • Unsolved
Collapse
Brand Logo
  1. Home
  2. Qt Development
  3. General and Desktop
  4. issue getting a lineEdit to update
QtWS25 Last Chance

issue getting a lineEdit to update

Scheduled Pinned Locked Moved Unsolved General and Desktop
c++lineeditfunction
18 Posts 3 Posters 1.4k Views
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • D Dean21
    24 Jan 2023, 12:25

    @jsulm I did try adding the [this] but is still the same, I do expect it to be an empty string on the first time the code is ran because I havent sent anything on MQTT. Just to let you know I have a raspberry pi that when I run a cmd line command sends the MQTT data.
    I feel as though I need to be able to have the function call inside of the onMessageRecieved function, as when I receive a message I then want to update the lineEdit

    J Offline
    J Offline
    jsulm
    Lifetime Qt Champion
    wrote on 24 Jan 2023, 12:28 last edited by
    #8

    @Dean21 Please post your current code, capturing "this" should work.
    Checking value of the string you're setting is also easy...

    https://forum.qt.io/topic/113070/qt-code-of-conduct

    D 1 Reply Last reply 24 Jan 2023, 12:45
    0
    • J jsulm
      24 Jan 2023, 12:28

      @Dean21 Please post your current code, capturing "this" should work.
      Checking value of the string you're setting is also easy...

      D Offline
      D Offline
      Dean21
      wrote on 24 Jan 2023, 12:45 last edited by
      #9

      @jsulm I can post the code but it uses a library that had to be downloaded and setup inside the .pro, just cause if you try to run it without then it wont work, plus you would need to be able to send MQTT data to it, to check if the line edit updates when it should.

      J 1 Reply Last reply 24 Jan 2023, 12:46
      0
      • D Dean21
        24 Jan 2023, 12:45

        @jsulm I can post the code but it uses a library that had to be downloaded and setup inside the .pro, just cause if you try to run it without then it wont work, plus you would need to be able to send MQTT data to it, to check if the line edit updates when it should.

        J Offline
        J Offline
        jsulm
        Lifetime Qt Champion
        wrote on 24 Jan 2023, 12:46 last edited by
        #10

        @Dean21 I don't ask you to post all your code, just the relevant parts (especially your current connect statement with captured "this").

        https://forum.qt.io/topic/113070/qt-code-of-conduct

        D 1 Reply Last reply 24 Jan 2023, 12:55
        0
        • J jsulm
          24 Jan 2023, 12:46

          @Dean21 I don't ask you to post all your code, just the relevant parts (especially your current connect statement with captured "this").

          D Offline
          D Offline
          Dean21
          wrote on 24 Jan 2023, 12:55 last edited by
          #11

          @jsulm sorry for long reply I have to wait 10 minutes between post as I am new user, for completness the code for the QMMqtClient.h and .cpp files are found here in case you wanted to see that as well https://github.com/KostiantynBushko/QMosqMqttClient

          #include "widget.h"
          #include "./ui_widget.h"
          #include <QPalette>
          #include <QDebug>
          #include <QTimer>
          
          
          #include <string>
          #include <cstring>
          #include <iostream>
          #include <time.h>
          #include </home/dave/mosquitto/include/mosquitto.h> //needed for mosquitto MQTT
          
          //-----for qt qrapper for mosquitto-----
          #include <QCoreApplication>
          #include <QTime>
          #include "QMMqttClient.h"
          //--------------------------------------
          
          QString msg_as_qstring;
          
          
          Widget::Widget(QWidget *parent)
              : QWidget(parent)
              , ui(new Ui::Widget)
          
          {
              ui->setupUi(this);
          
          
                  QObject::connect(&client, &QMMqttClient::onConnected, this ,[this](){
                      qDebug() << " QMMqttClient::onConnected handler, subscribe to topic...";
                      client.subscribeTopic("command/stop");
                  });
          
                  QObject::connect(&client, &QMMqttClient::onMessageReceived, [this](const QString &topic, const QByteArray &msg) {
                      msg_as_qstring = QString(msg);
                      qDebug() << "test value is"<< msg_as_qstring;
                      //msg_functionality();
                  });
          
                  qDebug() << "msg_as_qstring"<< msg_as_qstring;
          
                  //msg_functionality(); // issue here
          
          //        /* An example of unsecure connection */
                  client.initialize("12", RPi_IP, 1883);
          
                  client.connect();
          
          
          }
          
          Widget::~Widget()
          {
              delete ui;
          }
          
          
          void Widget::msg_functionality(){
          
              qDebug() << "here";
              qDebug() << msg_as_qstring;
              ui->Light_Level_Line_Edit->setText(msg_as_qstring);
          }
          
          J J 2 Replies Last reply 24 Jan 2023, 13:01
          0
          • D Dean21
            24 Jan 2023, 12:55

            @jsulm sorry for long reply I have to wait 10 minutes between post as I am new user, for completness the code for the QMMqtClient.h and .cpp files are found here in case you wanted to see that as well https://github.com/KostiantynBushko/QMosqMqttClient

            #include "widget.h"
            #include "./ui_widget.h"
            #include <QPalette>
            #include <QDebug>
            #include <QTimer>
            
            
            #include <string>
            #include <cstring>
            #include <iostream>
            #include <time.h>
            #include </home/dave/mosquitto/include/mosquitto.h> //needed for mosquitto MQTT
            
            //-----for qt qrapper for mosquitto-----
            #include <QCoreApplication>
            #include <QTime>
            #include "QMMqttClient.h"
            //--------------------------------------
            
            QString msg_as_qstring;
            
            
            Widget::Widget(QWidget *parent)
                : QWidget(parent)
                , ui(new Ui::Widget)
            
            {
                ui->setupUi(this);
            
            
                    QObject::connect(&client, &QMMqttClient::onConnected, this ,[this](){
                        qDebug() << " QMMqttClient::onConnected handler, subscribe to topic...";
                        client.subscribeTopic("command/stop");
                    });
            
                    QObject::connect(&client, &QMMqttClient::onMessageReceived, [this](const QString &topic, const QByteArray &msg) {
                        msg_as_qstring = QString(msg);
                        qDebug() << "test value is"<< msg_as_qstring;
                        //msg_functionality();
                    });
            
                    qDebug() << "msg_as_qstring"<< msg_as_qstring;
            
                    //msg_functionality(); // issue here
            
            //        /* An example of unsecure connection */
                    client.initialize("12", RPi_IP, 1883);
            
                    client.connect();
            
            
            }
            
            Widget::~Widget()
            {
                delete ui;
            }
            
            
            void Widget::msg_functionality(){
            
                qDebug() << "here";
                qDebug() << msg_as_qstring;
                ui->Light_Level_Line_Edit->setText(msg_as_qstring);
            }
            
            J Offline
            J Offline
            jsulm
            Lifetime Qt Champion
            wrote on 24 Jan 2023, 13:01 last edited by
            #12

            @Dean21 said in issue getting a lineEdit to update:

            QObject::connect(&client, &QMMqttClient::onMessageReceived, [this](const QString &topic, const QByteArray &msg) {
            msg_as_qstring = QString(msg);
            qDebug() << "test value is"<< msg_as_qstring;
            //msg_functionality();
            });

            What exact error do you get if you uncomment msg_functionality()?

            https://forum.qt.io/topic/113070/qt-code-of-conduct

            D 1 Reply Last reply 24 Jan 2023, 13:10
            1
            • D Dean21
              24 Jan 2023, 12:55

              @jsulm sorry for long reply I have to wait 10 minutes between post as I am new user, for completness the code for the QMMqtClient.h and .cpp files are found here in case you wanted to see that as well https://github.com/KostiantynBushko/QMosqMqttClient

              #include "widget.h"
              #include "./ui_widget.h"
              #include <QPalette>
              #include <QDebug>
              #include <QTimer>
              
              
              #include <string>
              #include <cstring>
              #include <iostream>
              #include <time.h>
              #include </home/dave/mosquitto/include/mosquitto.h> //needed for mosquitto MQTT
              
              //-----for qt qrapper for mosquitto-----
              #include <QCoreApplication>
              #include <QTime>
              #include "QMMqttClient.h"
              //--------------------------------------
              
              QString msg_as_qstring;
              
              
              Widget::Widget(QWidget *parent)
                  : QWidget(parent)
                  , ui(new Ui::Widget)
              
              {
                  ui->setupUi(this);
              
              
                      QObject::connect(&client, &QMMqttClient::onConnected, this ,[this](){
                          qDebug() << " QMMqttClient::onConnected handler, subscribe to topic...";
                          client.subscribeTopic("command/stop");
                      });
              
                      QObject::connect(&client, &QMMqttClient::onMessageReceived, [this](const QString &topic, const QByteArray &msg) {
                          msg_as_qstring = QString(msg);
                          qDebug() << "test value is"<< msg_as_qstring;
                          //msg_functionality();
                      });
              
                      qDebug() << "msg_as_qstring"<< msg_as_qstring;
              
                      //msg_functionality(); // issue here
              
              //        /* An example of unsecure connection */
                      client.initialize("12", RPi_IP, 1883);
              
                      client.connect();
              
              
              }
              
              Widget::~Widget()
              {
                  delete ui;
              }
              
              
              void Widget::msg_functionality(){
              
                  qDebug() << "here";
                  qDebug() << msg_as_qstring;
                  ui->Light_Level_Line_Edit->setText(msg_as_qstring);
              }
              
              J Offline
              J Offline
              JonB
              wrote on 24 Jan 2023, 13:03 last edited by
              #13

              @Dean21
              ...And while you are answering @jsulm please show widget.h just in case...

              1 Reply Last reply
              0
              • J jsulm
                24 Jan 2023, 13:01

                @Dean21 said in issue getting a lineEdit to update:

                QObject::connect(&client, &QMMqttClient::onMessageReceived, [this](const QString &topic, const QByteArray &msg) {
                msg_as_qstring = QString(msg);
                qDebug() << "test value is"<< msg_as_qstring;
                //msg_functionality();
                });

                What exact error do you get if you uncomment msg_functionality()?

                D Offline
                D Offline
                Dean21
                wrote on 24 Jan 2023, 13:10 last edited by
                #14

                @jsulm that doesnt give any errors but I also dont see the debug "here" and same as before lineEdit doesnt update

                and here is the widget.h file code

                #ifndef WIDGET_H
                #define WIDGET_H
                
                #include <QWidget>
                #include <string>
                #include "QMMqttClient.h"
                
                QT_BEGIN_NAMESPACE
                namespace Ui { class Widget; }
                QT_END_NAMESPACE
                
                class Widget : public QWidget
                {
                    Q_OBJECT
                
                public:
                    Widget(QWidget *parent = nullptr);
                    ~Widget();
                    QMMqttClient client;
                
                
                
                private slots:
                    void on_pushButton_clicked();
                    void int_or_string_LV();
                    void int_or_string_HV();
                    void Display_Int_Error(int);
                    void Empty_string_Error(int);
                    void Display_Range_Error(int);
                    void Display_Default(int);
                    void Display_success_msg(int);
                    void Vbias_min_max_check(QString, int);
                    void msg_functionality();
                
                    void on_lineEdit_returnPressed();
                
                    void on_HV_pushButton_pressed();
                
                    void on_HV_lineEdit_returnPressed();
                
                
                private:
                    Ui::Widget *ui;
                
                
                };
                #endif // WIDGET_H
                
                
                J 1 Reply Last reply 24 Jan 2023, 13:15
                0
                • D Dean21
                  24 Jan 2023, 13:10

                  @jsulm that doesnt give any errors but I also dont see the debug "here" and same as before lineEdit doesnt update

                  and here is the widget.h file code

                  #ifndef WIDGET_H
                  #define WIDGET_H
                  
                  #include <QWidget>
                  #include <string>
                  #include "QMMqttClient.h"
                  
                  QT_BEGIN_NAMESPACE
                  namespace Ui { class Widget; }
                  QT_END_NAMESPACE
                  
                  class Widget : public QWidget
                  {
                      Q_OBJECT
                  
                  public:
                      Widget(QWidget *parent = nullptr);
                      ~Widget();
                      QMMqttClient client;
                  
                  
                  
                  private slots:
                      void on_pushButton_clicked();
                      void int_or_string_LV();
                      void int_or_string_HV();
                      void Display_Int_Error(int);
                      void Empty_string_Error(int);
                      void Display_Range_Error(int);
                      void Display_Default(int);
                      void Display_success_msg(int);
                      void Vbias_min_max_check(QString, int);
                      void msg_functionality();
                  
                      void on_lineEdit_returnPressed();
                  
                      void on_HV_pushButton_pressed();
                  
                      void on_HV_lineEdit_returnPressed();
                  
                  
                  private:
                      Ui::Widget *ui;
                  
                  
                  };
                  #endif // WIDGET_H
                  
                  
                  J Offline
                  J Offline
                  jsulm
                  Lifetime Qt Champion
                  wrote on 24 Jan 2023, 13:15 last edited by
                  #15

                  @Dean21 Do you see the debug output from

                  qDebug() << "test value is"<< msg_as_qstring;
                  

                  ?

                  https://forum.qt.io/topic/113070/qt-code-of-conduct

                  D 1 Reply Last reply 24 Jan 2023, 13:23
                  0
                  • J jsulm
                    24 Jan 2023, 13:15

                    @Dean21 Do you see the debug output from

                    qDebug() << "test value is"<< msg_as_qstring;
                    

                    ?

                    D Offline
                    D Offline
                    Dean21
                    wrote on 24 Jan 2023, 13:23 last edited by Dean21
                    #16

                    @jsulm sorry my bad I had the "here" accidentally commented, when I run the program is my full output, I do see both "here" and test value is

                    msg_as_qstring ""
                    void QMMqttClient::initialize(const QString&, const QString&, int) "12" "130.246.58.64" 1883
                    void QMMqttClient::connect()
                    virtual void QMMqttClient::on_connect(int)  Sucessfully connected to host:  "130.246.58.64"  port:  1883
                     QMMqttClient::onConnected handler, subscribe to topic...
                    void QMMqttClient::subscribeTopic(const QString&) : topic:  "command/stop"
                    virtual void QMMqttClient::on_subscribe(int, int, const int*)  mid:  1 , QoS:  1
                    

                    And then when I receive an MQTT message this is what is displayed I added to the msg_functionality to add new debug line its shown below

                    void Widget::msg_functionality(){
                        qDebug() << "here";
                        qDebug() << "msg as string "<< msg_as_qstring;
                        ui->Light_Level_Line_Edit->setText(msg_as_qstring);
                    }
                    
                    Topic:  "command/stop" , Msg:  "2\u0000"
                    test value is "2\u0000"
                    here
                    msg as string  "2\u0000"
                    

                    edit: Oh I just seen that it is working now but I feel we didnt change anything

                    J 1 Reply Last reply 24 Jan 2023, 13:26
                    0
                    • D Dean21
                      24 Jan 2023, 13:23

                      @jsulm sorry my bad I had the "here" accidentally commented, when I run the program is my full output, I do see both "here" and test value is

                      msg_as_qstring ""
                      void QMMqttClient::initialize(const QString&, const QString&, int) "12" "130.246.58.64" 1883
                      void QMMqttClient::connect()
                      virtual void QMMqttClient::on_connect(int)  Sucessfully connected to host:  "130.246.58.64"  port:  1883
                       QMMqttClient::onConnected handler, subscribe to topic...
                      void QMMqttClient::subscribeTopic(const QString&) : topic:  "command/stop"
                      virtual void QMMqttClient::on_subscribe(int, int, const int*)  mid:  1 , QoS:  1
                      

                      And then when I receive an MQTT message this is what is displayed I added to the msg_functionality to add new debug line its shown below

                      void Widget::msg_functionality(){
                          qDebug() << "here";
                          qDebug() << "msg as string "<< msg_as_qstring;
                          ui->Light_Level_Line_Edit->setText(msg_as_qstring);
                      }
                      
                      Topic:  "command/stop" , Msg:  "2\u0000"
                      test value is "2\u0000"
                      here
                      msg as string  "2\u0000"
                      

                      edit: Oh I just seen that it is working now but I feel we didnt change anything

                      J Offline
                      J Offline
                      jsulm
                      Lifetime Qt Champion
                      wrote on 24 Jan 2023, 13:26 last edited by
                      #17

                      @Dean21 So, works now.
                      Depending on what data you're receiving this could be wrong:

                      msg_as_qstring = QString(msg);
                      

                      https://forum.qt.io/topic/113070/qt-code-of-conduct

                      D 1 Reply Last reply 24 Jan 2023, 13:34
                      0
                      • J jsulm
                        24 Jan 2023, 13:26

                        @Dean21 So, works now.
                        Depending on what data you're receiving this could be wrong:

                        msg_as_qstring = QString(msg);
                        
                        D Offline
                        D Offline
                        Dean21
                        wrote on 24 Jan 2023, 13:34 last edited by Dean21
                        #18

                        @jsulm the data that is sent is in the form of a char array, example,

                        char message[]  = "message here";
                        

                        I use QString because before I was using std::string and I was getting errors when trying to submit that to the line edit, I think conversion type errors, using a QString removed that error and thus I just stuck with it.

                        edit: oh it is working now, I feel like we didnt change anything though and we were just going through debug statements

                        1 Reply Last reply
                        0

                        17/18

                        24 Jan 2023, 13:26

                        • Login

                        • Login or register to search.
                        17 out of 18
                        • First post
                          17/18
                          Last post
                        0
                        • Categories
                        • Recent
                        • Tags
                        • Popular
                        • Users
                        • Groups
                        • Search
                        • Get Qt Extensions
                        • Unsolved