Cannot refresh QT's view while changing model - qt

Question

I am learning how to integrate qml with c++.
I've implemented a custom model class StringListModel, which inherits QAbstratListModel.
And, I have a main.qml to use StringListModel.
QML view can show initial values correctly.
I have another thread to change model periodically.
I do use beginResetModel() and endResetModel() to indicate model changed.
However, while the model keeps been changed, the view didn't update.
Here is my source code.
Please teach me what went wrong.
THANKS!
=== main.qml ===
Rectangle {
width: 360
height: 360
Grid {
id: gridview
columns: 2
spacing: 20
Repeater {
id: repeater
model: StringListModel {
id:myclass
}
delegate: Text {
text: model.title
}
}
}
=== custom class.h ===
class StringListModel : public QAbstractListModel{
Q_OBJECT
public:
StringListModel(QObject *parent = 0);
int rowCount(const QModelIndex &parent = QModelIndex()) const;
QVariant data(const QModelIndex &index, int role) const;
QHash<int, QByteArray> roleNames() const;
void newItem();
private:
QStringList stringList;
};
class UpdateThread : public QThread {
Q_OBJECT
StringListModel *mMyClass;
public:
UpdateThread(StringListModel * myClass);
protected:
void run();
};
=== custom class.cpp ===
StringListModel::StringListModel(QObject *parent) : QAbstractListModel(parent)
{
stringList << "one" << "two" << "three";
QThread *thread = new UpdateThread(this);
thread->start();
}
int StringListModel::rowCount(const QModelIndex &parent) const
{
return stringList.count();
}
QVariant StringListModel::data(const QModelIndex &index, int role) const
{
if (!index.isValid())
return QVariant();
if (index.row() >= stringList.size())
return QVariant();
if (role == Qt::UserRole + 1)
return stringList.at(index.row());
else
return QVariant();
}
QHash<int, QByteArray> StringListModel::roleNames() const
{
QHash<int, QByteArray> roles;
roles[Qt::UserRole + 1] = "title";
return roles;
}
void StringListModel::newItem()
{
qDebug() << "size: " << stringList.size();
beginResetModel();
stringList << "new";
endResetModel();
}
UpdateThread::UpdateThread(StringListModel * myClass)
{
mMyClass = myClass;
}
void UpdateThread::run()
{
while (true) {
mMyClass->newItem();
msleep(1000);
}
}

Answer 1

You're dutifully ignoring the matters of synchronizing access to the model. When you have any object that's accessed from more than one thread (even something as "simple" as a raw pointer), you must deal with the ramifications of such access.
I suggest you don't mess with threads unless you have measurements showing that you'll benefit.