Problem emiting signal in QTreeWidgetItem's subclass

[jpn]

Perhaps you could even use the built-in signal QTreeWidget::itemClicked(QTreeWidget* item, int column) and simply cast the passed item:

connect(treeWidget, SIGNAL(itemClicked(QTreeWidget*, int)), receiver, SLOT(doSomething(QTreeWidget*, int)));
 
void Receiver::doSomething(QTreeWidget* item, int column)
{
    MyTreeWidgetItem* myItem = dynamic_cast<MyTreeWidgetItem*>(item);
    if (myItem)
    {
        // yes, it's a "MyTreeWidgetItem", do something with it's "element"
    }
}

connect(treeWidget, SIGNAL(itemClicked(QTreeWidget*, int)), receiver, SLOT(doSomething(QTreeWidget*, int)));

void Receiver::doSomething(QTreeWidget* item, int column)
{
    MyTreeWidgetItem* myItem = dynamic_cast<MyTreeWidgetItem*>(item);
    if (myItem)
    {
        // yes, it's a "MyTreeWidgetItem", do something with it's "element"
    }
}

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Actually you could store the element information as QTreeWidgetItem's user data, without the need of subclassing QTreeWidgetItem.

[Shawn]

Perhaps you could even use the built-in signal QTreeWidget::itemClicked(QTreeWidget* item, int column) and simply cast the passed item:

connect(treeWidget, SIGNAL(itemClicked(QTreeWidget*, int)), receiver, SLOT(doSomething(QTreeWidget*, int)));
 
void Receiver::doSomething(QTreeWidget* item, int column)
{
    MyTreeWidgetItem* myItem = dynamic_cast<MyTreeWidgetItem*>(item);
    if (myItem)
    {
        // yes, it's a "MyTreeWidgetItem", do something with it's "element"
    }
}

connect(treeWidget, SIGNAL(itemClicked(QTreeWidget*, int)), receiver, SLOT(doSomething(QTreeWidget*, int)));

void Receiver::doSomething(QTreeWidget* item, int column)
{
    MyTreeWidgetItem* myItem = dynamic_cast<MyTreeWidgetItem*>(item);
    if (myItem)
    {
        // yes, it's a "MyTreeWidgetItem", do something with it's "element"
    }
}

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Actually you could store the element information as QTreeWidgetItem's user data, without the need of subclassing QTreeWidgetItem.

I did what you said,

QObject::connect(ui.treeWidget, SIGNAL(itemClicked(QTreeWidgetItem*, int)), this, SLOT(testslot(QTreeWidgetItem*, int)));
void test::testslot(QTreeWidgetItem* item, int column)
{
	QString str = item->text(column);
	QMessageBox::information(0, "testslot", str, QMessageBox::Ok);
}

QObject::connect(ui.treeWidget, SIGNAL(itemClicked(QTreeWidgetItem*, int)), this, SLOT(testslot(QTreeWidgetItem*, int)));
void test::testslot(QTreeWidgetItem* item, int column)
{
	QString str = item->text(column);
	QMessageBox::information(0, "testslot", str, QMessageBox::Ok);
}

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The strange thing is that the message box appears many times when I click on any item. 22 times on my laptop and 38 or 39 times on my workstation...

[Shawn]

The strange thing is that the message box appears many times when I click on any item. 22 times on my laptop and 38 or 39 times on my workstation...

I test it using a local static variable, and found that the exact times the testslot has been called is 22. Why it behaves like this ?

[jpn]

Do you call QObject::connect() in a loop?

[Shawn]

Sorry, stupid mistake

I connected in a recursion function...

After replace it to the constractor, it works well

Thanks very much for your help!

[Shawn]

Perhaps you could even use the built-in signal QTreeWidget::itemClicked(QTreeWidget* item, int column) and simply cast the passed item:

connect(treeWidget, SIGNAL(itemClicked(QTreeWidget*, int)), receiver, SLOT(doSomething(QTreeWidget*, int)));
 
void Receiver::doSomething(QTreeWidget* item, int column)
{
    MyTreeWidgetItem* myItem = dynamic_cast<MyTreeWidgetItem*>(item);
    if (myItem)
    {
        // yes, it's a "MyTreeWidgetItem", do something with it's "element"
    }
}

connect(treeWidget, SIGNAL(itemClicked(QTreeWidget*, int)), receiver, SLOT(doSomething(QTreeWidget*, int)));

void Receiver::doSomething(QTreeWidget* item, int column)
{
    MyTreeWidgetItem* myItem = dynamic_cast<MyTreeWidgetItem*>(item);
    if (myItem)
    {
        // yes, it's a "MyTreeWidgetItem", do something with it's "element"
    }
}

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Actually you could store the element information as QTreeWidgetItem's user data, without the need of subclassing QTreeWidgetItem.

The program works now, but I still doesn't understand your code. Especially for the dynamic_cast function, how can it get the "element" information only by MyTreeWidgetItem's parent class ?

If you have time, can you explain it a little bit? If you can recommend some metarial that I can study this by myself, I will appreciate it as well.

[marcel]

Go to this address and download Thinking in C++( Bruce Eckel) and read the chapter on polymorphism: http://www.mindview.net/Books/DownloadSites.

Regards