QListView setItemDelegate problem sizeHint and paint not being called

steveq

Hey All,

I am trying to implement this:
https://forum.qt.io/topic/91480/implementing-chat-type-listview-with-text-bubbles

If I do this, it works a treat::

#include "mainwindow.h"
#include "listviewdelegate.h"
#include <QApplication>

#include <QtWidgets>

int main(int argc, char *argv[])
{
	QApplication a(argc, argv);
//	MainWindow w;
//	w.show();

	// create some data and put it in a model
	QStandardItemModel mymodel;
	QStandardItem *item1 = new QStandardItem("This is item one");
	item1->setData("Incoming", Qt::UserRole + 1);
	mymodel.appendRow(item1);
	QStandardItem *item2 = new QStandardItem("This is item <b>two</b>, it is a very long item, but it's not the item's fault, it is me typing all this text.");
	item2->setData("Outgoing", Qt::UserRole + 1);
	mymodel.appendRow(item2);
	QStandardItem *item3 = new QStandardItem("This is the third item");
	item3->setData("Incoming", Qt::UserRole + 1);
	mymodel.appendRow(item3);

	// create a view and set our data
	QListView listview;
	listview.setResizeMode(QListView::Adjust);
	listview.setWordWrap(true);
	listview.setVerticalScrollMode(QAbstractItemView::ScrollPerPixel);
	listview.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
	listview.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
	listview.setModel(&mymodel);
	listview.setMinimumSize(200,350);

	// NOW tell the view to rely on out custom delegate for drawing
	listview.setItemDelegate(new ListViewDelegate());

	// show it
	listview.show();

	return a.exec();
}

However I don't want to use it this way, I want to uncomment the MainWindow lines:

#include "mainwindow.h"
#include "listviewdelegate.h"
#include <QApplication>

#include <QtWidgets>

int main(int argc, char *argv[])
{
	QApplication a(argc, argv);
	MainWindow w;
	w.show();

	// create some data and put it in a model
//	QStandardItemModel mymodel;
//	QStandardItem *item1 = new QStandardItem("This is item one");
//	item1->setData("Incoming", Qt::UserRole + 1);
//	mymodel.appendRow(item1);
//	QStandardItem *item2 = new QStandardItem("This is item <b>two</b>, it is a very long item, but it's not the item's fault, it is me typing all this text.");
//	item2->setData("Outgoing", Qt::UserRole + 1);
//	mymodel.appendRow(item2);
//	QStandardItem *item3 = new QStandardItem("This is the third item");
//	item3->setData("Incoming", Qt::UserRole + 1);
//	mymodel.appendRow(item3);

//	// create a view and set our data
//	QListView listview;
//	listview.setResizeMode(QListView::Adjust);
//	listview.setWordWrap(true);
//	listview.setVerticalScrollMode(QAbstractItemView::ScrollPerPixel);
//	listview.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
//	listview.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
//	listview.setModel(&mymodel);
//	listview.setMinimumSize(200,350);

//	// NOW tell the view to rely on out custom delegate for drawing
//	listview.setItemDelegate(new ListViewDelegate());

//	// show it
//	listview.show();

	return a.exec();
}

And then do this in the MainWindow class creation:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "listviewdelegate.h"

#include <QStandardItemModel>
#include <QListView>

MainWindow::MainWindow(QWidget *parent) :
	QMainWindow(parent),
	ui(new Ui::MainWindow)
{
	ui->setupUi(this);

	QStandardItemModel mymodel;
	QStandardItem *item1 = new QStandardItem("This is item one");
	item1->setData("Incoming", Qt::UserRole + 1);
	mymodel.appendRow(item1);
	QStandardItem *item2 = new QStandardItem("This is item <b>two</b>, it is a very long item, but it's not the item's fault, it is me typing all this text.");
	item2->setData("Outgoing", Qt::UserRole + 1);
	mymodel.appendRow(item2);
	QStandardItem *item3 = new QStandardItem("This is the third item");
	item3->setData("Incoming", Qt::UserRole + 1);
	mymodel.appendRow(item3);

	// create a view and set our data
	ui->listview->setResizeMode(QListView::Adjust);
	ui->listview->setWordWrap(true);
	ui->listview->setVerticalScrollMode(QAbstractItemView::ScrollPerPixel);
	ui->listview->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
	ui->listview->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
	ui->listview->setModel(&mymodel);
	ui->listview->setMinimumSize(200,350);

	// NOW tell the view to rely on out custom delegate for drawing
	ui->listview->setItemDelegate(new ListViewDelegate);
}

MainWindow::~MainWindow()
{
	delete ui;
}

That is, I want to use the QListView I've created in QDesigner, but if I do this, sizeHint and paint never get called and I just get a blank QListView.

Can someone help me please?

Many thanks,

Steve Q. :-)

Christian Ehrlicher

@steveq said in QListView setItemDelegate problem sizeHint and paint not being called:

QStandardItemModel mymodel;

C++ basics - how long do you think does this object lives?

steveq

Oh dear... that is a little embarrassing.

Can't believe I looked over this countless times.

Sorry to waste your time... thanks @Christian-Ehrlicher

Christian Ehrlicher

No problem, nice to get it solved :)