QT如何检查表格小部件类型

Question

I have added a checkbox to my QTableWidget like this:

     QWidget *checkBoxWidget = new QWidget();
     QCheckBox *checkBox = new QCheckBox();      // We declare and initialize the checkbox
     QHBoxLayout *layoutCheckBox = new QHBoxLayout(checkBoxWidget); // create a layer with reference to the widget
     layoutCheckBox->addWidget(checkBox);            // Set the checkbox in the layer
     layoutCheckBox->setAlignment(Qt::AlignCenter);  // Center the checkbox
     layoutCheckBox->setContentsMargins(0,0,0,0);    // Set the zero padding
    checkBox->setChecked(true);
   ui->my_table_view->setCellWidget(0,1, checkBoxWidget); // 

The problem is when I read that table cell how I will know that the cell holds a checkbox , a radio-button or a text .

Currently, my getValuesAt function can read text from the cell but I am not sure how to check the checkbox 's state

getValuesAt(int row_number, int column_number)
{
    if(!ui->my_table_view->item(row_number,column_number)){
        return "";
    }else{
        return ui->my_table_view->item(row_number,column_number)->text();
    }
}

I tried to read widget type like this but it returns 0

QTableWidgetItem::ItemType res = ui->my_table_view->item(row_number,column_number)->Type;

Answer 1

Please notice that, if you put a widget in a cell, the corresponding item will be null unless you don't explicitly add one:

tableWidget->setCellWidget(0, 0, new QCheckBox());
qDebug() << tableWidget->item(0, 0); //yields 0x0

When inspecting a cell , you could first check if it has a widget and, if it doesn't, check if the underlying item is null or not:

for(int column=0; column<columns; ++column)
{
    QWidget * cellWidget = tableWidget->cellWidget(row, column);
    if(cellWidget != nullptr)
    {
        QCheckBox * checkbox = dynamic_cast<QCheckBox*>(cellWidget);
        if(checkbox != nullptr)
        {
            qDebug() << checkbox->isChecked();
        }
        else
        {
           //some other widget type ...
        }
    }
    else
    {
        QTableWidgetItem * item = tableWidget->item(row, column);
        if(item != nullptr)
        {
            qDebug() << item->text();
        }
        else
        {
           //this is an empty cell
        }
    }
}

Answer 2

You can access class name of any QObject derived class by

QString className(someObject->metaObject()->className());

For you example it would be like

QString className(ui->my_table_view->item(row_number,column_number)->metaObject()->className());

Answer 3

You can cast a pointer of a QWidget instance to a concrete type pointer, eg. QCheckBox* and check the result to be not nullptr . If it is not nullptr , it is an instance of that type.

QWidget *widget = new QCheckBox();
if (dynamic_cast<QCheckBox*>(widget) != widget) {
  // widget is a QCheckBox
}

if (dynamic_cast<QRadioButton*>(widget) == nullptr) {
  // widget is not a QRadioButton
}

You can use other casting options as well. Like qobject_cast or static_cast .

This method is useful not only for Qt classes. You can check whether the coming pointer (no matter where it comes from) is an instance of this or that class (or inherited class). But in other cases, you might not have a qobject_cast option, because it is Qt specific. But others remain applicable.