如何显示通过C++中的另一个类添加到ListView，QML的数据

Question

我需要在QLinkedList容器中显示所有数据(这是任务提供的(。我创建了两个类，DataObject用于ListView中的委托，Glav用于带有DataObject对象的容器。我有一个按钮，可以在上面向容器添加数据(Glav类中的addItem函数(。数据已添加，但不会显示在ListView中。如何显示它们？我通过信号试过了，但没用。这是该项目的完整代码。

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QStringListModel>
#include <QQmlContext>
#include <QLinkedList>
#include <QQuickView>
#include <container.h>
#include <dataobject.h>
#include "glav.h"
//#include <container.cpp>
int main(int argc, char *argv[])
{
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
qmlRegisterUncreatableType<tile::Glav>( "Tile", 1, 0, "DataItem", "interface" );
qmlRegisterType<tile::Glav>( "Tile", 1, 0, "Glav");
const QUrl url(QStringLiteral("qrc:/main.qml"));
QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
&app, [url](QObject *obj, const QUrl &objUrl) {
if (!obj && url == objUrl)
QCoreApplication::exit(-1);
}, Qt::QueuedConnection);
engine.load(url);
return app.exec();
}

main.qml

import QtQuick 2.12
import QtQuick.Controls 2.5
//import App 1.0
import Tile 1.0
ApplicationWindow {
width: 640
height: 480
visible: true
title: qsTr("Scroll")
//    Container {
//        id: container
//    }
Glav {
id: glav
}

Row {
id: buttons
spacing: 20
padding: 10
anchors.horizontalCenter: parent.horizontalCenter
RoundButton {
padding: 20
text: "add item"
onClicked: {
glav.addItem()
listView.currentIndex = -1
}
}
Connections{
target: myModelObjectWhichWasSetAsContextProperty
onRowsInserted: console.log("rows were inserted")
}
ScrollView {
anchors.fill: parent
anchors.topMargin: buttons.implicitHeight + 10
ListView {
id: listView
width: parent.width
model: glav.list
//required model
delegate: Text {
property var d
d: model.modelData.id
text: model.modelData.name
}
removeDisplaced: Transition {
NumberAnimation { properties: "x,y"; duration: 100; easing.type: Easing.InOutQuad }
}
}
}
}

dataobject.h

#ifndef DATAOBJECT_H
#define DATAOBJECT_H
#include <QObject>
namespace tile {
class DataObject : public QObject
{
Q_OBJECT
Q_PROPERTY(QString name READ name WRITE setName NOTIFY changed)
Q_PROPERTY(QString color READ color WRITE setColor NOTIFY changed)
Q_PROPERTY(int id READ id WRITE setId NOTIFY changed)
public:
explicit DataObject(QString name = "Wana", QString color = "red", int id = 1, QObject *parent = nullptr);
QString name();
void setName(const QString &name);
QString color();
void setColor(const QString &color);
int id() const;
void setId(int id);
signals:
void changed();
private:
QString m_name;
QString m_color;
int m_id;
};
}
#endif // DATAOBJECT_H

数据对象.cpp

#include "dataobject.h"
#include <QDebug>
namespace tile {
DataObject::DataObject(QString name, QString color, int id, QObject* parent) :
QObject(parent)
, m_name (name)
, m_color (color)
, m_id (id)
{
//new DataObject();
qDebug() << m_name;
//emit changed();
}
QString DataObject::name()
{
return m_name;
}
void DataObject::setName(const QString &name)
{
m_name = name;
qDebug() << m_name;
emit changed();
}
QString DataObject::color()
{
return m_color;
}
void DataObject::setColor(const QString &color)
{
m_color = color;
emit changed();
}
int DataObject::id() const
{
return m_id;
}
void DataObject::setId(int id)
{
m_id = id;
emit changed();
}
}

glav.h

#ifndef GLAV_H
#define GLAV_H
#include <QObject>
#include <QLinkedList>
namespace tile {
class Glav : public QObject
{
Q_OBJECT
Q_PROPERTY( QLinkedList<QObject *> list READ list CONSTANT )
public:
explicit Glav(QObject *parent = nullptr);
//QLinkedList<QObject *> list();
//void setList(const QLinkedList<QObject *> &list);
Q_INVOKABLE QLinkedList<QObject *> pollist();
Q_INVOKABLE void addItem();
//    Q_INVOKABLE QVariant pol();

signals:
void changed();
private:
QLinkedList<QObject *> m_list;
QLinkedList<QObject *> list();
};
}
#endif // GLAV_H

glav.cpp

#include "glav.h"
#include "dataobject.h"
#include <QDebug>
#include <QAbstractListModel>
namespace tile {
Glav::Glav(QObject *parent) : QObject(parent)
{
QLinkedList<QObject *> dataList = {
new DataObject("Item 1", "red"),
new DataObject("Item 2", "green"),
new DataObject("Item 3", "blue"),
new DataObject("Item 9", "yellow")
};
m_list << dataList;
QVariant::fromValue(m_list);
}
QLinkedList<QObject *> Glav::list()
{
return m_list;
}
//void Glav::setList(const QLinkedList<QObject *> &list)
//{
//    m_list = list;
//}

//QVariant Glav::pol(){
//     QVariant re = QVariant::fromValue(m_list);
//    return re;
//}

QLinkedList<QObject *> Glav::pollist()
{
//qDebug() << QVariant::fromValue(m_list);
//QLinkedList<QObject *> f = m_list;
//QVariant::fromValue(m_list);
//qDebug() <<m_list;
return m_list;
}
void Glav::addItem()
{
qDebug() << m_list.count();
m_list << new DataObject();
qDebug() << m_list.count();
emit changed();
}
}

Answer 1

您的Glav类有一个changed()信号，但它什么都不做，因为您的列表属性是常量(Q_PROPERTY( QLinkedList<QObject *> list READ list CONSTANT )(

您应该将其更改为：

Q_PROPERTY(QLinkedList<QObject*> list READ list NOTIFY changed)

通过这种方式，您可以通过发出changed()信号让ListView知道列表刚刚更改。

此外，最好根据信号对应的属性来命名信号：listChanged。

有关Q_PROPERTY如何在官方文档中工作的更多信息：https://doc.qt.io/qt-5/properties.html