How can I change my screen in my GUI application when a thread stops running.

RoBlox

these are my files:
navthread.h

#pragma once

#include <QObject>
#include <QThread>
#include <QtCore>

class NavThread : public QThread
{
  Q_OBJECT
public:
  explicit NavThread(QObject *parent = 0);
  bool Stop;
  void run();
  bool active;
  int i;

signals:
  void over();

public slots:

private:
  QMutex mutex;

};

navthread.cpp



void NavThread::run()
{
    ros::NodeHandle ros_nh; // Start the roscpp node by creating a ros node handle

    // referece frame
    std::string ref_frame = "map"; // or use "base_link" for targets in the frame relative to the robots position
    // declare an array of PointStamped messages to keep track of the waypoints
    std::vector<geometry_msgs::PointStamped> waypoints;
    // declare 'goal' to use it to keep each waipoints coordinates (double)
    move_base_msgs::MoveBaseGoal goal;
    uint8_t task = 0;
    // parse waypoints from YAML file
    bool built = buildWaypointsFromFile(waypoints);
    if ( !built )
    {
      ROS_FATAL( "building waypoints from a file failed" );
    }

  ros::Rate rate(1); // in Hz, makes a best effort at maintaining a particular rate for a loop
    while(this->active)
    {
    switch (task)
             {
             case 0:
               mutex.lock();
               ROS_INFO("Moving to pick up place");
               bun(ref_frame, goal, waypoints, 0);
               task = 1;
               mutex.unlock();
               break;

             case 1:
               mutex.lock();
               if(!this->Stop){
                 bun(ref_frame, goal, waypoints, 0);
                 Stop = true;
               }
               ROS_INFO("Loading of goods ... (waiting 5 seconds)");
               ros::Duration(5).sleep();
               ROS_INFO("Moving to drop off zone");
               // funtion call to run waypoint navigation to waypoint 1
               bun(ref_frame, goal, waypoints, this->i);
               ros::Duration(5).sleep();
               task = 2;
               mutex.unlock();
               break;


             case 2:
               if(!this->Stop){
               bun(ref_frame, goal, waypoints, this->i);
               Stop = true;
               }
               ROS_INFO_ONCE("Click on OTP Button");
               this->active = false;
               break;

             }
  }
    ROS_INFO_ONCE("Emitting");
    emit over();
    QThread::quit();
//}
}

loading_area.h

#pragma once

#include "navthread.h"

namespace Ui {
class Loading_area;
}

class Loading_area : public QWidget
{
  Q_OBJECT

public:
  explicit Loading_area(QWidget *parent = nullptr);
  ~Loading_area();
  NavThread *nav;
  ros::NodeHandle ros_nh;


public slots:
  void on_go_clicked();

private slots:

  void onfinishing();

private:
  Ui::Loading_area *ui;
  NavThread change;

};

loading_area.cpp

#include "loading_area.h"
#include "ui_loading_area.h"

Loading_area::Loading_area(QWidget *parent) :
  QWidget(parent),
  ui(new Ui::Loading_area)
{
  ui->setupUi(this);
  connect(&change, SIGNAL(over()), this, SLOT(onfinishing()));
  nav = new NavThread(this);
}

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

void Loading_area::on_go_clicked()
{
    QString input = ui->lineEdit->text();

    nav->active = true;
    nav->start();
//    nav->wait();
    while(nav->isFinished())
    {
    ui->stackedWidget->setCurrentIndex(2);
    }
}

void Loading_area::onfinishing()
{
  ui->stackedWidget->setCurrentIndex(2);
}

Ignore unnecessary code....what I am doing is I am starting the navthread from my on_go_clicked slot in my loading_area.cpp file. In my navthread file I have all the code for robot navigation......what I want to do is when my robot reaces it's final destination I want to change my screen on my QT gui basically when my navthread finishes I want change my GUI screen. I tried calling nav->isFinished() (nav is defined from navthread you can see it in loading_area header file) in my Loading_area::on_go_clicked() slot but it didn't work (as you can see).....I also used

nav->wait() //(which is commented)
ui->stackedWidget->setCurrentIndex(2);

this time it worked and screen did got changed after bot reached the goal but I couldn't click anything (application freezed) on my gui application until this thread fininshed working. Is there a way I can change my screen as soon as this thread finishes working but also while thread runs I can click buttons and stuff on my gui application.

JonB

@RoBlox said in How can I change my screen in my GUI application when a thread stops running.:

Ignore unnecessary code....

Very hard. What you are supposed to do is reduce the code to minimal for us to look at, not make us have to try to determine what is relevant and what is not....

    nav->active = true;
    nav->start();
//    nav->wait();
    while(nav->isFinished())
    {
    ui->stackedWidget->setCurrentIndex(2);
    }

Whatever nav is --- a thread?? --- you need to do no more than nav->start() and then exit this slot. Any "waiting" or "while-looping" will block your GUI. You need a signal to be raised when "nav thread" finishes, then you change current widget when your slot receives that.

RoBlox

@JonB sorry for that I have made the changes to my question......also nav is a pointer pointing towards navthread class which is derived from QThread. I didn't get what you meant can you elaborate a bit please.

Christian Ehrlicher

@RoBlox said in How can I change my screen in my GUI application when a thread stops running.:

I didn't get what you meant can you elaborate a bit please.

Don't call

while(nav->isFinished())
{
ui->stackedWidget->setCurrentIndex(2);
}

But use signals and sots to not block the main event loop.

RoBlox

@Christian-Ehrlicher I also tried that above you can see that my NavThread::run() function emits a signal over which I have connected to the void Loading_area::onfinishing() slot in my loading_area.cpp file......if that's what you meant it's not working....idk what's wrong there

JonB

@RoBlox
... and if it still doesn't work after getting rid of the while loop, put a qDebug() into onfinishing() to make sure it's being hit....

You could also put suitable breakpoints into a debugger to examine behaviour.

RoBlox

@JonB my code does exit out of while loop I have put a print statement to check that above my emit command in NavThread.cpp run() function

RoBlox

@JonB but apparently my slot is not receiving the signal....idk why
I checked it by adding qDebug to it.

Christian Ehrlicher

@RoBlox said in How can I change my screen in my GUI application when a thread stops running.:

connect(&change, SIGNAL(over()), this, SLOT(onfinishing()));

This is wrong... at least it's not the thread you're starting below. You've two NavThread objects in your Loading_area (one object and one pointer) - fix your code.

RoBlox

@Christian-Ehrlicher Ohhh my bad.....Thanks :)