<![CDATA[lose precesion when qtreeview show double value]]>my json contains double value like 32.6743408794, but when i load and show it ,it only shows 32.67。When debug in QJsonTreeItem* QJsonTreeItem::load(const QJsonValue& value, QJsonTreeItem* parent) fuction , i found the value in child is correct actually, so i think it's a treeview widget problem not jsonmodel. If someone could give me some advice, i'll appreciate. ：)
alt text
alt text

]]>https://forum.qt.io/topic/143644/lose-precesion-when-qtreeview-show-double-valueRSS for NodeFri, 24 Apr 2026 03:35:51 GMTWed, 15 Mar 2023 07:30:54 GMT60<![CDATA[Reply to lose precesion when qtreeview show double value on Wed, 15 Mar 2023 12:59:21 GMT]]>@Chris-Kawa thank for ur explaination. after custom my delegate , i solved this problem.alt text

and when click double value item, should reimplement setEditorData function to specify the format,otherwise the double value will shrink too. below is my key code,hope it helps someone else.

QWidget* XtrTaskViewDelegate::createEditor(QWidget* parent, const QStyleOptionViewItem& option, const QModelIndex& index) const
{
	return QStyledItemDelegate::createEditor(parent, option, index);
}

void XtrTaskViewDelegate::setEditorData(QWidget* editor, const QModelIndex& index) const
{
	if (index.data().type() == QVariant::Double)
	{
		QDoubleSpinBox* doubleSpinBox = static_cast<QDoubleSpinBox*>(editor);

		doubleSpinBox->setDecimals(10);
		doubleSpinBox->setValue(index.data().toDouble());
	}
	else 
	{
		QStyledItemDelegate::setEditorData(editor, index);
	}
}
]]>https://forum.qt.io/post/751107https://forum.qt.io/post/751107Wed, 15 Mar 2023 12:59:21 GMT<![CDATA[Reply to lose precesion when qtreeview show double value on Wed, 15 Mar 2023 10:14:56 GMT]]>@Christian-Ehrlicher Well yes, but also no :) data() returns a QVariant, which does not need to be a string. In case of numbers it's often preferable to return the actual type, like double or int and let the view display it appropriately. This allows to have different views display the data from the same model differently e.g. have one view display a rounded number and another (e.g. a "detailed view") to show the full thing. You could do the conversion in the model, but it limits your further options and formatting shouldn't really be the model's job I think. The way I interpret DisplayRole is "the data to be displayed", not "how to display the data".

]]>https://forum.qt.io/post/751092https://forum.qt.io/post/751092Wed, 15 Mar 2023 10:14:56 GMT<![CDATA[Reply to lose precesion when qtreeview show double value on Wed, 15 Mar 2023 10:01:40 GMT]]>@Chris-Kawa Or simply return the correct formated value in data() for Qt::DisplayRole (this is what this role is for).

]]>https://forum.qt.io/post/751090https://forum.qt.io/post/751090Wed, 15 Mar 2023 10:01:40 GMT<![CDATA[Reply to lose precesion when qtreeview show double value on Wed, 15 Mar 2023 09:51:38 GMT]]>@WuYaZi QTreeView by default uses QStyledItemDelegate to paint its items and that uses the locale object to get the display text from the double value returned from the model data. See source. By default the precision is set to 6 digits, so either your particular locale overrides that or you have a custom item delegate that does the double to string conversion differently.

In any case you can provide a custom delegate if you want to override the way it displays numbers.

]]>https://forum.qt.io/post/751086https://forum.qt.io/post/751086Wed, 15 Mar 2023 09:51:38 GMT<![CDATA[Reply to lose precesion when qtreeview show double value on Wed, 15 Mar 2023 08:23:53 GMT]]>@Christian-Ehrlicher
thank for ur reply.
but i didn't want to change the type of such numberic value, cause i want to edit them through gui, if i return string , then when i save the json , a stringToDouble function will be added. I just wonder wheather there is a simpler way :

]]>https://forum.qt.io/post/751083https://forum.qt.io/post/751083Wed, 15 Mar 2023 08:23:53 GMT<![CDATA[Reply to lose precesion when qtreeview show double value on Wed, 15 Mar 2023 07:54:55 GMT]]>Fix your QJsonModel::data() function to return a proper string for Qt::DisplayRole.

]]>https://forum.qt.io/post/751081https://forum.qt.io/post/751081Wed, 15 Mar 2023 07:54:55 GMT<![CDATA[Reply to lose precesion when qtreeview show double value on Wed, 15 Mar 2023 07:42:15 GMT]]>btw, i use https://github.com/dridk/QJsonModel for my json model ,it's easy to use, but this problem annoy me.

]]>https://forum.qt.io/post/751080https://forum.qt.io/post/751080Wed, 15 Mar 2023 07:42:15 GMT