Question

我尝试使用QML TreeView模型。 Qt的例子不包括如何创建模型。我读了这个post并尝试使用@Tarod中的代码，但结果不是我的预期。

的main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include "animalmodel.h"
#include <qqmlcontext.h>
#include <qqml.h>

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    AnimalModel model;
    model.addAnimal("wolf", "Medium");
    model.addAnimal("Bear", "Large");

    QQmlApplicationEngine engine;
    QQmlContext *ctxt = engine.rootContext();
    ctxt->setContextProperty("myModel", &model);
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    if (engine.rootObjects().isEmpty())
        return -1;

    return app.exec();
}

animalmodel.h

#ifndef ANIMALMODEL_H
#define ANIMALMODEL_H

#include <QStandardItemModel>


class AnimalModel : public QStandardItemModel
{
    Q_OBJECT //The Q_OBJECT macro must appear in the private section of a class definition that declares its own signals and slots or that uses other services provided by Qt's meta-object system.
public:
    enum AnimalRoles {
        TypeRole = Qt::UserRole + 1,
        SizeRole
    };

    AnimalModel(QObject *parent = 0);

    Q_INVOKABLE void addAnimal(const QString &type, const QString &size);

    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const;

protected:
    QHash<int, QByteArray> roleNames() const;
};

#endif // ANIMALMODEL_H

animalmodel.cpp

#include "animalmodel.h"

AnimalModel::AnimalModel(QObject *parent)
    : QStandardItemModel(parent)
{

}

void AnimalModel::addAnimal(const QString &type, const QString &size)
{
    QStandardItem* entry = new QStandardItem();
    entry->setData(type, TypeRole);

    auto childEntry = new QStandardItem();
    childEntry->setData(size, SizeRole);
    entry->appendRow(childEntry);

    appendRow(entry);
}

QVariant AnimalModel::data(const QModelIndex & index, int role) const {
    QStandardItem *myItem = itemFromIndex(index);

    if (role == TypeRole)
        return myItem->data(TypeRole);
    else if (role == SizeRole) {
        if (myItem->child(0) != 0)
        {
            return myItem->child(0)->data(SizeRole);
        }
    }
    return QVariant();
}

QHash<int, QByteArray> AnimalModel::roleNames() const {
    QHash<int, QByteArray> roles;
    roles[TypeRole] = "type";
    roles[SizeRole] = "size";
    return roles;
}

main.qml

import QtQuick 2.6
import QtQuick.Window 2.2
import QtQuick.Controls 1.4


ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    menuBar: MenuBar {
        Menu {
            title: qsTr("&File")
            MenuItem {
                text: qsTr("&Open")
                onTriggered: messageDialog.show(qsTr("Open Action Triggered"));
            }
            MenuItem {
                text: qsTr("&Exit")
                onTriggered: Qt.quit();
            }
        }
    }


    TreeView {
        anchors.fill: parent
        model: myModel
        TableViewColumn {
            title: "Name"
            role: "type"
            width: 300
        }
        TableViewColumn {
            title: "Size"
            role: "size"
            width: 300
        }
    }
}

我得到的是这样的： Result

我想要的是动物类型的动物大小。

Answer 1

模型子分类是Qt中最糟糕的雷区之一。建议总是让它通过模型测试（https://wiki.qt.io/Model_Test）来查看是否所有内容都已正确实现。

另一方面，在90％的情况下，您根本不需要对模型进行子类化，因为Qt提供的默认模型工作得很好。我要做的就是使用QStandardItemModel，在C ++方面，只使用QAbstractItemModel接口（即强迫自己使用QAbstractItemModel* model = new QStandardItemModel(/*parent*/);），如果将来你觉得你真的需要重新实现模型（为了提高效率）您只需在现有代码中更改1行。

在你的情况下：

void AnimalModel::addAnimal(const QString &type, const QString &size)
{
    if(columnCount()==0) insertColumn(0); // make sure there is at least 1 column
    insertRow(rowCount()); // add a row to the root
    const QModelIndex addedIdx = index(rowCount()-1,0);
    setData(addedIdx, type, TypeRole); // set the root data
    insertRow(rowCount(addedIdx),addedIdx ); // add 1 row ...
    insertColumn(0,addedIdx ); // ... and 1 column to the added root row
    setData(index(0,0,addedIdx), size, SizeRole); // set the data to the child

}

为QML TreeView创建模型

1 个答案: