QProgressBar and ActiveX

[neo_qt]

With Qt Creator, I have inserted a progress bar using the QProgressBar object. I would like the progress bar displaying the busy mode while doing some operations in Excel ( called via ActiveX)

If I am not wrong QAxObject will start another thread so the GUI should not hang out during the ActiveX call/operations. Could you tell me what I did wrong ?

Here is my code

// progressBar busy mode 
ui->progressBar->setMinimum(0);
ui->progressBar->setMaximum(0);
ui->progressBar->show();

// Kick Excel using ActiveX
CoInitialize(0);
QAxObject excel( "Excel.Application", 0 );

//Some Excel operations... during few seconds

// Quit Excel
excel.dynamicCall("Quit()");

// Revert to normal mode
ui->progressBar->setMaximum(100);

[hskoglund]

Hi, while QAxObject can do many fancy things, starting another thread outside of the GUI is not of them :-(

But if you add some QThread/worker code and move the QAxObject stuff in there, it will work nicely with the GUI.
Here's an example that updates a progress bar: create an empty vanilla Widget app, add axcontainer to the QT line in the .pro file, then change mainwindow.h to this:

#include <QMainWindow>
#include "windows.h"    // for the CoInitialize() call
#include "QAxObject"
#include <QThread>

namespace Ui { class MainWindow; }

class ExcelWorker : public QObject
{
    Q_OBJECT

public slots:
    void doWork(int n)
    {
        CoInitialize(0);
        auto excel = new QAxObject("Excel.Application",0);
        if (nullptr == excel)
            return;

        excel->setProperty("Visible",true);
        auto workbooks = excel->querySubObject("Workbooks");
        auto workbook  = workbooks->querySubObject("Add");
        auto sheets    = workbook->querySubObject("Worksheets");
        auto sheet     = sheets->querySubObject("Item(int)",1);

        for (int i = 0; (i < n); ++i)
        {
            sheet->querySubObject("Cells(int,int)",i % 10 + 1,i / 10 + 1)->setProperty("Value",i);
            QThread::msleep(100);  // simulate some heavy munging

            emit oneReady(i);
        }
    }

signals:
    void oneReady(int i);
};

class MainWindow : public QMainWindow
{
    Q_OBJECT
    QThread excelThread;

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private slots:
    void oneReadyFromExcel(int i);
    void on_pushButton_clicked();

signals:
    void doExcelWork(int n);

private:
    Ui::MainWindow *ui;
};

and change the mainwindow.cpp to this:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "qtimer.h"

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

    auto ew = new ExcelWorker;
    ew->moveToThread(&excelThread);
    connect(this,&MainWindow::doExcelWork,ew,&ExcelWorker::doWork);
    connect(ew,&ExcelWorker::oneReady,this,&MainWindow::oneReadyFromExcel);

    excelThread.start();
}

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

void MainWindow::on_pushButton_clicked()
{
    emit doExcelWork(100);
}

void MainWindow::oneReadyFromExcel(int i)
{
    ui->progressBar->setValue(i);
}

Finally add one progress bar and a push button and connect the clicked() signal from the push button to starting Excel and you're good to go.

Edit: I just tested it, it runs ok but crashes when exiting the app, the example is missing the cleanup of the worker thread and quitting Excel, but I think you'll get the idea anyhow..

[neo_qt]

@hskoglund Thank you very much for the explanation and the code. I have not tested fully your code yet but now I understand why my code did not work as I expect.