如何在 QML 中编辑 QQmlListProperty
How to edit QQmlListProperty in QML
如果我们想在 QML 中使用自定义 C++ 对象列表,我们可以使用 QQmlListProperty
在 QML 中注册时,我们需要指定一个函数,QML 将使用该函数读取列表。
文档指出,对于功能齐全的列表,我们需要使用此函数:
QQmlListProperty::QQmlListProperty(QObject *object, void *data, AppendFunction append,
CountFunction count, AtFunction at, ClearFunction clear)
这是我如何用 C++ 编写它的示例:
classwithlist.h
#ifndef CLASSWITHLIST_H
#define CLASSWITHLIST_H
#include <QObject>
#include <QQmlListProperty>
#include "element.h"
class Element;
class ClassWithList : public QObject
{
Q_OBJECT
Q_PROPERTY(QQmlListProperty<Element> elements READ getElements NOTIFY elementsChanged)
public:
explicit ClassWithList(QObject *parent = 0);
QQmlListProperty<Element> getElements();
void appendElements(QQmlListProperty<Element> *list, Element *e);
static int elementsCount(QQmlListProperty<Element> *list);
static Element* elementsAt(QQmlListProperty<Element> *list, int i);
static void elementsClear(QQmlListProperty<Element> *list);
signals:
void elementsChanged(QQmlListProperty<Element>);
private:
QList<Element *> m_elements;
};
#endif // CLASSWITHLIST_H
classwithlist.cpp
#include "classwithlist.h"
ClassWithList::ClassWithList(QObject *parent) : QObject(parent)
{
}
QQmlListProperty<Element> ClassWithList::getElements()
{
return QQmlListProperty<Element>(this, m_elements, &appendElements,&elementsCount,&elementsAt,&elementsClear);
}
void ClassWithList::appendElements(QQmlListProperty<Element> *list, Element *e)
{
ClassWithList *cwl = qobject_cast<ClassWithList*>(list->object);
if (cwl && e) {
cwl->m_elements.append(e);
}
}
int ClassWithList::elementsCount(QQmlListProperty<Element> *list)
{
ClassWithList *cwl = qobject_cast<ClassWithList*>(list->object);
if (cwl)
return cwl->m_elements.count();
return 0;
}
Element *ClassWithList::elementsAt(QQmlListProperty<Element> *list, int i)
{
ClassWithList *cwl = qobject_cast<ClassWithList*>(list->object);
if (cwl)
return cwl->m_elements.at(i);
return 0;
}
void ClassWithList::elementsClear(QQmlListProperty<Element> *list)
{
ClassWithList *cwl = qobject_cast<ClassWithList*>(list->object);
if (cwl) {
cwl->m_elements.clear();
}
}
在将 class 暴露给 QML 后,我在 QML 中有以下代码
ClassWithList {
Component.onCompleted: {
console.log(elements.length) // works
console.log(elements[0]) // works
// elements.push() // does not work
// elements.append() // does not work
// elements.clear() // does not work
// elements.at() // does not work
}
}
我可以使用将项目添加到列表或清除它的函数吗?如上所示,我可以通过使用 .length
和括号来使用函数 CountFunction
和 AtFunction
。我也可以使用 ClearFunction
和 AppendFunction
吗?
也许我不能用 QQmlListProperty
做到这一点,我应该使用 QAbstractListModel
?
编辑: 由于列表 属性 界面的变化,下面的答案不再完全正确。现在可以使用 push
附加对象(来自下面链接的文档):
Values can be dynamically added to the list by using the push method, as if it were a JavaScript Array
下面是原回答
您不能在 QML 中直接向 QQmlListProperty
添加元素或清除 QQmlListProperty
。要在 QML 中编辑 QQmlListProperty
,请为其分配一个新列表。
根据 QML list
documentation:
Any QQmlListProperty
value passed into QML from C++ is automatically converted into a list
value, and vice-versa.
Note that objects cannot be individually added to or removed from the list once created; to modify the contents of a list, it must be reassigned to a new list.
如果我们想在 QML 中使用自定义 C++ 对象列表,我们可以使用 QQmlListProperty
在 QML 中注册时,我们需要指定一个函数,QML 将使用该函数读取列表。
文档指出,对于功能齐全的列表,我们需要使用此函数:
QQmlListProperty::QQmlListProperty(QObject *object, void *data, AppendFunction append,
CountFunction count, AtFunction at, ClearFunction clear)
这是我如何用 C++ 编写它的示例:
classwithlist.h
#ifndef CLASSWITHLIST_H
#define CLASSWITHLIST_H
#include <QObject>
#include <QQmlListProperty>
#include "element.h"
class Element;
class ClassWithList : public QObject
{
Q_OBJECT
Q_PROPERTY(QQmlListProperty<Element> elements READ getElements NOTIFY elementsChanged)
public:
explicit ClassWithList(QObject *parent = 0);
QQmlListProperty<Element> getElements();
void appendElements(QQmlListProperty<Element> *list, Element *e);
static int elementsCount(QQmlListProperty<Element> *list);
static Element* elementsAt(QQmlListProperty<Element> *list, int i);
static void elementsClear(QQmlListProperty<Element> *list);
signals:
void elementsChanged(QQmlListProperty<Element>);
private:
QList<Element *> m_elements;
};
#endif // CLASSWITHLIST_H
classwithlist.cpp
#include "classwithlist.h"
ClassWithList::ClassWithList(QObject *parent) : QObject(parent)
{
}
QQmlListProperty<Element> ClassWithList::getElements()
{
return QQmlListProperty<Element>(this, m_elements, &appendElements,&elementsCount,&elementsAt,&elementsClear);
}
void ClassWithList::appendElements(QQmlListProperty<Element> *list, Element *e)
{
ClassWithList *cwl = qobject_cast<ClassWithList*>(list->object);
if (cwl && e) {
cwl->m_elements.append(e);
}
}
int ClassWithList::elementsCount(QQmlListProperty<Element> *list)
{
ClassWithList *cwl = qobject_cast<ClassWithList*>(list->object);
if (cwl)
return cwl->m_elements.count();
return 0;
}
Element *ClassWithList::elementsAt(QQmlListProperty<Element> *list, int i)
{
ClassWithList *cwl = qobject_cast<ClassWithList*>(list->object);
if (cwl)
return cwl->m_elements.at(i);
return 0;
}
void ClassWithList::elementsClear(QQmlListProperty<Element> *list)
{
ClassWithList *cwl = qobject_cast<ClassWithList*>(list->object);
if (cwl) {
cwl->m_elements.clear();
}
}
在将 class 暴露给 QML 后,我在 QML 中有以下代码
ClassWithList {
Component.onCompleted: {
console.log(elements.length) // works
console.log(elements[0]) // works
// elements.push() // does not work
// elements.append() // does not work
// elements.clear() // does not work
// elements.at() // does not work
}
}
我可以使用将项目添加到列表或清除它的函数吗?如上所示,我可以通过使用 .length
和括号来使用函数 CountFunction
和 AtFunction
。我也可以使用 ClearFunction
和 AppendFunction
吗?
也许我不能用 QQmlListProperty
做到这一点,我应该使用 QAbstractListModel
?
编辑: 由于列表 属性 界面的变化,下面的答案不再完全正确。现在可以使用 push
附加对象(来自下面链接的文档):
Values can be dynamically added to the list by using the push method, as if it were a JavaScript Array
下面是原回答
您不能在 QML 中直接向 QQmlListProperty
添加元素或清除 QQmlListProperty
。要在 QML 中编辑 QQmlListProperty
,请为其分配一个新列表。
根据 QML list
documentation:
Any
QQmlListProperty
value passed into QML from C++ is automatically converted into alist
value, and vice-versa.Note that objects cannot be individually added to or removed from the list once created; to modify the contents of a list, it must be reassigned to a new list.