从 QAbstractListModel 中删除行 [英] Remove rows from QAbstractListModel
问题描述
我有一个从 QAbstractListModel 派生的自定义模型，它暴露给 QML.我需要支持添加新项目和删除现有项目的操作.虽然插入操作没有任何问题，但删除操作会导致应用程序在调用 endRemoveRows() 函数时崩溃.
I have a custom model which derives from QAbstractListModel which is exposed to QML. I need to support operations to add new items and remove existing items. While insertion operation works without any problems, removal operation causes the application to crash while calling endRemoveRows() function.
void GPageModel::addNewPage()
{
if(m_pageList.count()<9)
{
beginInsertRows(QModelIndex(),rowCount(),rowCount());
GPage * page = new GPage();
QQmlEngine::setObjectOwnership(page,QQmlEngine::CppOwnership);
page->setParent(this);
page->setNumber(m_pageList.count());
page->setName("Page " + QString::number(m_pageList.count()+1));
m_pageList.append(page);
endInsertRows();
}
}
void GPageModel::removePage(const int index)
{
if(index>=0 && index<m_pageList.count())
{
beginRemoveRows(QModelIndex(),index,index);
qDebug()<<QString("beginRemoveRows(QModelIndex(),%1,%1)").arg(index);
GPage * page = m_pageList.at(index);
m_pageList.removeAt(index);
delete page;
endRemoveRows();
}
}
GPage 类派生自 QObject.在尝试调用 endRemoveRows() 时，试图找出导致应用程序崩溃的原因让我感到震惊.当调用 endRemoveRows() 时，我得到QList::at:索引超出范围"中的 ASSERT 失败".如何从 QAbsracListModel 中删除行?有没有其他办法?
The class GPage derives from QObject. I am struck trying to figure out what is causing the app to crash while trying to call endRemoveRows(). I get "ASSERT failure in QList::at: "index out of range"" when endRemoveRows() is called.How do I remove the rows from a QAbstracListModel? Is there any other way?
我在 Windows 7 64 位机器上使用 Qt 5.1.0.
I am using Qt 5.1.0 on a Windows 7 64 bit machine.
推荐答案
下面的代码对我来说很好用.您的问题可能在其他地方.由于使用了 Qt Quick Controls，这是针对 Qt 5 的.
The code below works fine for me. Your problem is probably elsewhere. This is for Qt 5 due to use of Qt Quick Controls.
有两个视图访问同一个模型，这在视觉上确认模型发出正确的信号以通知视图更改.页面添加和删除是通过标准的 insertRows 和 removeRows 方法完成的，通过 Q_INVOKABLE 导出.到目前为止，此模型上不需要任何自定义方法.Q_INVOKABLE 是 QML 和 QAbstractItemModel 之间的接口缺少的一些功能的解决方法.
There are two views accessing the same model, this visually confirms that the model emits proper signals to inform the views of the changes. The page additions and removals are done via the standard insertRows and removeRows methods, exported through Q_INVOKABLE. There's no need for any custom methods on this model, so far. The Q_INVOKABLE is a workaround for some missing functionality for the interface between QML and QAbstractItemModel.
main.cpp
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQuickWindow>
#include <QAbstractListModel>
#include <QQmlContext>
#include <QtQml>
class GPage : public QObject {
Q_OBJECT
Q_PROPERTY(QString name NOTIFY nameChanged MEMBER m_name)
Q_PROPERTY(int number NOTIFY numberChanged MEMBER m_number)
QString m_name;
int m_number;
public:
GPage(QObject * parent = 0) : QObject(parent), m_number(0) {}
GPage(QString name, int number, QObject * parent = 0) :
QObject(parent), m_name(name), m_number(number) {}
Q_SIGNAL void nameChanged(const QString &);
Q_SIGNAL void numberChanged(int);
};
class PageModel : public QAbstractListModel {
Q_OBJECT
QList<GPage*> m_pageList;
public:
PageModel(QObject * parent = 0) : QAbstractListModel(parent) {}
~PageModel() { qDeleteAll(m_pageList); }
int rowCount(const QModelIndex &) const Q_DECL_OVERRIDE {
return m_pageList.count();
}
QVariant data(const QModelIndex &index, int role) const Q_DECL_OVERRIDE {
if (role == Qt::DisplayRole || role == Qt::EditRole) {
return QVariant::fromValue<QObject*>(m_pageList.at(index.row()));
}
return QVariant();
}
bool setData(const QModelIndex &index, const QVariant &value, int role) Q_DECL_OVERRIDE {
Q_UNUSED(role);
GPage* page = value.value<GPage*>();
if (!page) return false;
if (page == m_pageList.at(index.row())) return true;
delete m_pageList.at(index.row());
m_pageList[index.row()] = page;
QVector<int> roles;
roles << role;
emit dataChanged(index, index, roles);
return true;
}
Q_INVOKABLE bool insertRows(int row, int count, const QModelIndex &parent = QModelIndex()) Q_DECL_OVERRIDE {
Q_UNUSED(parent);
beginInsertRows(QModelIndex(), row, row + count - 1);
for (int i = row; i < row + count; ++ i) {
QString const name = QString("Page %1").arg(i + 1);
GPage * page = new GPage(name, i + 1, this);
m_pageList.insert(i, page);
QQmlEngine::setObjectOwnership(page, QQmlEngine::CppOwnership);
}
endInsertRows();
return true;
}
Q_INVOKABLE bool removeRows(int row, int count, const QModelIndex &parent = QModelIndex()) Q_DECL_OVERRIDE {
Q_UNUSED(parent);
beginRemoveRows(QModelIndex(), row, row + count - 1);
while (count--) delete m_pageList.takeAt(row);
endRemoveRows();
return true;
}
};
int main(int argc, char *argv[])
{
PageModel model1;
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
model1.insertRows(0, 1);
engine.rootContext()->setContextProperty("model1", &model1);
qmlRegisterType<GPage>();
engine.load(QUrl("qrc:/main.qml"));
QObject *topLevel = engine.rootObjects().value(0);
QQuickWindow *window = qobject_cast<QQuickWindow *>(topLevel);
window->show();
return app.exec();
}
#include "main.moc"
main.qml
import QtQuick 2.0
import QtQml.Models 2.1
import QtQuick.Controls 1.0
ApplicationWindow {
width: 300; height: 300
Row {
width: parent.width
anchors.top: parent.top
anchors.bottom: column.top
Component {
id: commonDelegate
Rectangle {
width: view.width
implicitHeight: editor.implicitHeight + 10
color: "transparent"
border.color: "red"
border.width: 2
radius: 5
TextInput {
id: editor
anchors.margins: 1.5 * parent.border.width
anchors.fill: parent
text: edit.name // "edit" role of the model, to break the binding loop
onTextChanged: {
display.name = text;
model.display = display
}
}
}
}
ListView {
id: view
width: parent.width / 2
height: parent.height
model: DelegateModel {
id: delegateModel1
model: model1
delegate: commonDelegate
}
spacing: 2
}
ListView {
width: parent.width / 2
height: parent.height
model: DelegateModel {
model: model1
delegate: commonDelegate
}
spacing: 2
}
}
Column {
id: column;
anchors.bottom: parent.bottom
Row {
Button {
text: "Add Page";
onClicked: model1.insertRows(delegateModel1.count, 1)
}
Button {
text: "Remove Page";
onClicked: model1.removeRows(pageNo.value - 1, 1)
}
SpinBox {
id: pageNo
minimumValue: 1
maximumValue: delegateModel1.count;
}
}
}
}
main.qrc
<RCC>
<qresource prefix="/">
<file>main.qml</file>
</qresource>
</RCC>
这篇关于从 QAbstractListModel 中删除行的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
