QListWidget cannot add an item dynamically - c++

Question

In my Qt application, I want to add a new item dynamically into a listview. Besides I also used Signal & Slot to transfer data between forms so I have created 2 following forms:
mainwindow.h
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void ReceivedData(QString item);
private slots:
void on_btnAdd_clicked();
void on_btnCancel_clicked();
private:
Ui::MainWindow *ui;
void SetUpListName();
};
addform.h
class AddForm : public QDialog
{
Q_OBJECT
public:
explicit AddForm(QWidget *parent = 0);
~AddForm();
signals:
void SendData(QString item);
private slots:
void on_pushButton_clicked();
void on_pushButton_2_clicked();
private:
Ui::AddForm *ui;
MainWindow *main_window;
};
mainwindow.cpp
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
SetUpListName();
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::SetUpListName()
{
// Add 5 new elements
for (int i = 0; i < 5; i++) {
QString item = "Item " + QString::number(i);
ui->lwListItem->addItem(item);
}
}
void MainWindow::on_btnAdd_clicked()
{
// Open Add Form
AddForm add;
add.setModal(true);
add.exec();
}
void MainWindow::on_btnCancel_clicked()
{
this->close();
}
void MainWindow::ReceivedData(QString item)
{
// Check to receive data
qDebug() << "Item: " << item;
// Add a new item to list items
ui->lwListItem->addItem(item);
}
addform.cpp
AddForm::AddForm(QWidget *parent) :
QDialog(parent),
ui(new Ui::AddForm)
{
ui->setupUi(this);
main_window = new MainWindow();
connect(this, SIGNAL(SendData(QString)), main_window, SLOT(ReceivedData(QString)));
}
AddForm::~AddForm()
{
delete ui;
}
void AddForm::on_pushButton_clicked()
{
// Send data via Signal & Slot
emit SendData(ui->txtName->text());
}
void AddForm::on_pushButton_2_clicked()
{
this->close();
}
When I run the application, I got the data from Add form but the list view doesn’t add this item.
Does someone have any solutions?
Thanks!
P/S: You can download my source code at here

Answer 1

You are connecting the signal to the wrong object's slot. In the constructor of AddForm, you are creating a new MainWindow and connecting the signal to it's slot which means that the signal does not reach your real MainWindow, and the ReceivedData slot is adding the item to the wrong QListWidget. What you should do is this:
void MainWindow::on_btnAdd_clicked()
{
// Open Add Form
AddForm add;
connect(&add, SIGNAL(SendData(QString)), this, SLOT(ReceivedData(QString)));
add.setModal(true);
add.exec();
}
and remove the creation of a new MainWindow and corresponding connect call from the constructor of AddForm.