QTableWidget+QTableWidgetItem trouble

**Fastman** · 7th November 2007, 14:51

code(QT 4.3.1):

Qt Code:

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void HSM::setTable()
{
 
	ui.tableWidget->setRowCount(30);
	ui.tableWidget->setColumnCount(10);
 
	ui.tableWidget->setHorizontalHeaderLabels(
		QStringList() << tr("Task")
		<< tr("Time")
		<< tr("Group")
		<< tr("Object")
		<< tr("File")
		<< tr("ID_OBJ")
		<< tr("State")
		<< tr("Prc")
		<< tr("ID_SYS")
		<< tr("RootPath"));
 
	Items = new QTableWidgetItem(tr("Task"),QTableWidgetItem::Type);
	Items->setIcon(QIcon(QPixmap(":/HSM/Resources/Add.png")));
 
	ui.tableWidget->resizeRowsToContents();  
	ui.tableWidget->resizeColumnsToContents(); 
}

void HSM::setTable()
{

	ui.tableWidget->setRowCount(30);
	ui.tableWidget->setColumnCount(10);

	ui.tableWidget->setHorizontalHeaderLabels(
		QStringList() << tr("Task")
		<< tr("Time")
		<< tr("Group")
		<< tr("Object")
		<< tr("File")
		<< tr("ID_OBJ")
		<< tr("State")
		<< tr("Prc")
		<< tr("ID_SYS")
		<< tr("RootPath"));

	Items = new QTableWidgetItem(tr("Task"),QTableWidgetItem::Type);
	Items->setIcon(QIcon(QPixmap(":/HSM/Resources/Add.png")));

	ui.tableWidget->resizeRowsToContents();  
	ui.tableWidget->resizeColumnsToContents(); 
}

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Qt Code:

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void HSM::setTableData()
{
 
	for (int row = 0 ; row < ui.tableWidget->rowCount() ;++row)
	{
		ui.tableWidget->setItem(row,0,Items); 
	}
	ui.tableWidget->resizeRowsToContents();  
	ui.tableWidget->resizeColumnsToContents(); 
 
}

void HSM::setTableData()
{

	for (int row = 0 ; row < ui.tableWidget->rowCount() ;++row)
	{
		ui.tableWidget->setItem(row,0,Items); 
	}
	ui.tableWidget->resizeRowsToContents();  
	ui.tableWidget->resizeColumnsToContents(); 

}

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All well works but at closing the app the mistake jumps out.

The mistake occurs here:

d:\qt4\src\gui\itemviews\qtablewidget.cpp

Qt Code:

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void QTableModel::clearContents()
{
    for (int i = 0; i < tableItems.count(); ++i) {
        if (tableItems.at(i)) {
            tableItems.at(i)->view = 0;
            delete tableItems.at(i);  <--ERROR
            tableItems[i] = 0;
        }
    }
    reset();
}

void QTableModel::clearContents()
{
    for (int i = 0; i < tableItems.count(); ++i) {
        if (tableItems.at(i)) {
            tableItems.at(i)->view = 0;
            delete tableItems.at(i);  <--ERROR
            tableItems[i] = 0;
        }
    }
    reset();
}

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and tableItems.count() = 300. (10*30 ????)
but i'am have only 30 items !!!

Where at me a mistake. Also what it is necessary to make to correct a code?

**jpn** · 7th November 2007, 15:02

Yes, you do actually have 30*10=300 items. The mistake is that you set the same single item into every cell. You should create a separate item into each cell:

Qt Code:

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void HSM::setTableData()
{
 
	for (int row = 0 ; row < ui.tableWidget->rowCount() ;++row)
	{
		QTableWidgetItem* item = new QTableWidgetItem(tr("Task"));
		item->setIcon(QIcon(QPixmap(":/HSM/Resources/Add.png")));
		ui.tableWidget->setItem(row,0,item); 
	}
	ui.tableWidget->resizeRowsToContents();  
	ui.tableWidget->resizeColumnsToContents(); 
 
}

void HSM::setTableData()
{

	for (int row = 0 ; row < ui.tableWidget->rowCount() ;++row)
	{
		QTableWidgetItem* item = new QTableWidgetItem(tr("Task"));
		item->setIcon(QIcon(QPixmap(":/HSM/Resources/Add.png")));
		ui.tableWidget->setItem(row,0,item); 
	}
	ui.tableWidget->resizeRowsToContents();  
	ui.tableWidget->resizeColumnsToContents(); 

}

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**Fastman** · 7th November 2007, 15:07

i'am stupid

Thx !

**Fastman** · 9th November 2007, 09:42

Originally Posted by jpn

Yes, you do actually have 30*10=300 items. The mistake is that you set the same single item into every cell. You should create a separate item into each cell:

Qt Code:

Switch view

void HSM::setTableData()
{
 
	for (int row = 0 ; row < ui.tableWidget->rowCount() ;++row)
	{
		QTableWidgetItem* item = new QTableWidgetItem(tr("Task"));
		item->setIcon(QIcon(QPixmap(":/HSM/Resources/Add.png")));
		ui.tableWidget->setItem(row,0,item); 
	}
	ui.tableWidget->resizeRowsToContents();  
	ui.tableWidget->resizeColumnsToContents(); 
 
}

void HSM::setTableData()
{

	for (int row = 0 ; row < ui.tableWidget->rowCount() ;++row)
	{
		QTableWidgetItem* item = new QTableWidgetItem(tr("Task"));
		item->setIcon(QIcon(QPixmap(":/HSM/Resources/Add.png")));
		ui.tableWidget->setItem(row,0,item); 
	}
	ui.tableWidget->resizeRowsToContents();  
	ui.tableWidget->resizeColumnsToContents(); 

}

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Whether there will be memory leak if function setTableData () is caused in me each 5 seconds for display of changes in the table?

**jpn** · 9th November 2007, 09:49

No, that shouldn't leak memory since QTableWidget deletes the old item if you set a new item into cell. But you definitely don't want to re-create all the items every time in setTableData(). Create the items once in constructor or so, and just set the data in setTableData():

Qt Code:

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QTableWidgetItem* item = ui.tableWidget->item(row, col);
item->setSomething(...);

QTableWidgetItem* item = ui.tableWidget->item(row, col);
item->setSomething(...);

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**Fastman** · 9th November 2007, 10:41

Originally Posted by jpn

No, that shouldn't leak memory since QTableWidget deletes the old item if you set a new item into cell. But you definitely don't want to re-create all the items every time in setTableData(). Create the items once in constructor or so, and just set the data in setTableData():

Qt Code:

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QTableWidgetItem* item = ui.tableWidget->item(row, col);
item->setSomething(...);

QTableWidgetItem* item = ui.tableWidget->item(row, col);
item->setSomething(...);

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Hmm... not work

Qt Code:

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class HSM : public QDialog
{
	Q_OBJECT
...
...
...
private:
	QTableWidgetItem* itemArchive;
	QTableWidgetItem* itemRestore;
	QTableWidgetItem* itemDelete;
...
...
...

class HSM : public QDialog
{
	Q_OBJECT
...
...
...
private:
	QTableWidgetItem* itemArchive;
	QTableWidgetItem* itemRestore;
	QTableWidgetItem* itemDelete;
...
...
...

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Qt Code:

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HSM::HSM(QWidget *parent, Qt::WFlags flags)
	: QDialog(parent, flags)
{
 
...
...
...
	itemArchive = new QTableWidgetItem(tr("Archive"));
	itemRestore = new QTableWidgetItem(tr("Restore"));
	itemDelete = new QTableWidgetItem(tr("Delete"));
...
...
...

HSM::HSM(QWidget *parent, Qt::WFlags flags)
	: QDialog(parent, flags)
{

...
...
...
	itemArchive = new QTableWidgetItem(tr("Archive"));
	itemRestore = new QTableWidgetItem(tr("Restore"));
	itemDelete = new QTableWidgetItem(tr("Delete"));
...
...
...

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Qt Code:

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void HSM::setTableData()
{
	sTskInfoGUI sTaskGUI;
	db_work db;
 
	sTaskGUI = db.GetTaskToGUI();
	db.CloseDB();
 
	for (int row = 0 ; row < sTaskGUI.nCmd.size() ;++row)
	{
 
		if (sTaskGUI.nCmd.at(row) == 1)
		{
			itemArchive = ui.tableWidget->item(row,0);
			itemArchive->setIcon(QIcon(QPixmap(":/HSM/Resources/archive.png")));
			itemArchive->setBackground(QColor::fromRgb(200,255,104,100));
			//ui.tableWidget->setItem(row,0,itemArchive);
 
		}
		if (sTaskGUI.nCmd.at(row) == 2)
		{
			itemRestore = ui.tableWidget->item(row,0);
			itemRestore->setIcon(QIcon(QPixmap(":/HSM/Resources/restore.png")));
			itemRestore->setBackground(QColor::fromRgb(115,150,255,100));
			//ui.tableWidget->setItem(row,0,itemRestore);
		}
		if (sTaskGUI.nCmd.at(row) == 3)
		{
			itemDelete = ui.tableWidget->item(row,0);
			itemDelete->setIcon(QIcon(QPixmap(":/HSM/Resources/del.png")));
			itemDelete->setBackground(QColor::fromRgb(255,100,120,100));
			//ui.tableWidget->setItem(row,0,itemDelete);
		}
...
...
...

void HSM::setTableData()
{
	sTskInfoGUI sTaskGUI;
	db_work db;

	sTaskGUI = db.GetTaskToGUI();
	db.CloseDB();

	for (int row = 0 ; row < sTaskGUI.nCmd.size() ;++row)
	{
		
		if (sTaskGUI.nCmd.at(row) == 1)
		{
			itemArchive = ui.tableWidget->item(row,0);
			itemArchive->setIcon(QIcon(QPixmap(":/HSM/Resources/archive.png")));
			itemArchive->setBackground(QColor::fromRgb(200,255,104,100));
			//ui.tableWidget->setItem(row,0,itemArchive);

		}
		if (sTaskGUI.nCmd.at(row) == 2)
		{
			itemRestore = ui.tableWidget->item(row,0);
			itemRestore->setIcon(QIcon(QPixmap(":/HSM/Resources/restore.png")));
			itemRestore->setBackground(QColor::fromRgb(115,150,255,100));
			//ui.tableWidget->setItem(row,0,itemRestore);
		}
		if (sTaskGUI.nCmd.at(row) == 3)
		{
			itemDelete = ui.tableWidget->item(row,0);
			itemDelete->setIcon(QIcon(QPixmap(":/HSM/Resources/del.png")));
			itemDelete->setBackground(QColor::fromRgb(255,100,120,100));
			//ui.tableWidget->setItem(row,0,itemDelete);
		}
...
...
...

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Exception in code :
d:\qt4\src\gui\itemviews\qtablewidget.cpp

Qt Code:

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inline void QTableWidgetItem::setIcon(const QIcon &aicon)
{ setData(Qt::DecorationRole, aicon); }

inline void QTableWidgetItem::setIcon(const QIcon &aicon)
{ setData(Qt::DecorationRole, aicon); }

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**jpn** · 9th November 2007, 10:49

QTableWidget::item() returns 0 which means there is no item in such cell and so you are dereferencing a null pointer. Did you actually call QTableWidget::setItem() anywhere?

Qt Code:

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itemArchive = new QTableWidgetItem(tr("Archive"));
itemRestore = new QTableWidgetItem(tr("Restore"));
itemDelete = new QTableWidgetItem(tr("Delete"));
ui.tableWidget->setItem(0,0,itemArchive); // <--
ui.tableWidget->setItem(1,0,itemRestore); // <--
ui.tableWidget->setItem(2,0,itemDelete);  // <--

itemArchive = new QTableWidgetItem(tr("Archive"));
itemRestore = new QTableWidgetItem(tr("Restore"));
itemDelete = new QTableWidgetItem(tr("Delete"));
ui.tableWidget->setItem(0,0,itemArchive); // <--
ui.tableWidget->setItem(1,0,itemRestore); // <--
ui.tableWidget->setItem(2,0,itemDelete);  // <--

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**Fastman** · 9th November 2007, 11:28

Originally Posted by jpn

QTableWidget::item() returns 0 which means there is no item in such cell and so you are dereferencing a null pointer. Did you actually call QTableWidget::setItem() anywhere?

Qt Code:

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itemArchive = new QTableWidgetItem(tr("Archive"));
itemRestore = new QTableWidgetItem(tr("Restore"));
itemDelete = new QTableWidgetItem(tr("Delete"));
ui.tableWidget->setItem(0,0,itemArchive); // <--
ui.tableWidget->setItem(1,0,itemRestore); // <--
ui.tableWidget->setItem(2,0,itemDelete);  // <--

itemArchive = new QTableWidgetItem(tr("Archive"));
itemRestore = new QTableWidgetItem(tr("Restore"));
itemDelete = new QTableWidgetItem(tr("Delete"));
ui.tableWidget->setItem(0,0,itemArchive); // <--
ui.tableWidget->setItem(1,0,itemRestore); // <--
ui.tableWidget->setItem(2,0,itemDelete);  // <--

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no effect

Exception in code :
d:\qt4\src\gui\itemviews\qtablewidget.cpp

Qt Code:

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inline void QTableWidgetItem::setIcon(const QIcon &aicon){ setData(Qt::DecorationRole, aicon); }

inline void QTableWidgetItem::setIcon(const QIcon &aicon){ setData(Qt::DecorationRole, aicon); }

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**jpn** · 9th November 2007, 11:48

There are 3 places in your code in which you pick an item at certain cell:

Qt Code:

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...
itemArchive = ui.tableWidget->item(row,0);
...
itemRestore = ui.tableWidget->item(row,0);
...
itemRestore = ui.tableWidget->item(row,0);
...

...
itemArchive = ui.tableWidget->item(row,0);
...
itemRestore = ui.tableWidget->item(row,0);
...
itemRestore = ui.tableWidget->item(row,0);
...

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On the other hand, you have created an item only into cells (0,0), (1,0) and (2,0). If "row" is anything else than 0-2, you'll get a crash. This is most likely the case of yours.

**Fastman** · 9th November 2007, 13:18

Ok

Thx for you help

**jpn** · 9th November 2007, 17:42

Let me correct one thing. I just re-read my previous message and I want to make sure I don't get misundestood. Of course, calling QTableWidget::item() with any possible parameters doesn't cause a crash:

Qt Code:

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QTableWidgetItem* item = tableWidget->item(1234, 5678);

QTableWidgetItem* item = tableWidget->item(1234, 5678);

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But the point is that in case no item exists in such cell, QTableWidget::item() returns 0. Then, dereferencing a null pointer is what causes the crash:

Qt Code:

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item->setSomething();

item->setSomething();

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**Fastman** · 9th November 2007, 18:06

How to make so that last column it was leveled by a right edge of the table ?

Qt Code:

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void HSM::setTableData()
{
	sTskInfoGUI sTaskGUI;
	db_work db;
 
	sTaskGUI = db.GetTaskToGUI();
	db.CloseDB();...
...
...
		itemRootPatch->setText(sTaskGUI.cRootPath.at(row));
		ui.tableWidget->setItem(row,9,itemRootPatch);
	}
 
	ui.tableWidget->resizeRowsToContents();  
	ui.tableWidget->resizeColumnsToContents(); 
 
}

void HSM::setTableData()
{
	sTskInfoGUI sTaskGUI;
	db_work db;

	sTaskGUI = db.GetTaskToGUI();
	db.CloseDB();...
...
...
		itemRootPatch->setText(sTaskGUI.cRootPath.at(row));
		ui.tableWidget->setItem(row,9,itemRootPatch);
	}

	ui.tableWidget->resizeRowsToContents();  
	ui.tableWidget->resizeColumnsToContents(); 

}

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Here so my form looks.

**jpn** · 9th November 2007, 18:24

You can either use QHeaderView::setResizeMode() and pass QHeaderView::Stretch:

Qt Code:

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ui.tableWidget->horizontalHeader()->setResizeMode(10, QHeaderView::Stretch);

ui.tableWidget->horizontalHeader()->setResizeMode(10, QHeaderView::Stretch);

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Or you can use a "shortcut" (which QTreeView uses by default):

Qt Code:

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ui.tableWidget->horizontalHeader()->setStretchLastSection(true);

ui.tableWidget->horizontalHeader()->setStretchLastSection(true);

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**Fastman** · 10th November 2007, 12:19

many Thx !

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