Question

我有一个模特和一个qml。

Model.cpp：

Model::Model(QObject *parent): QAbstractListModel(parent)
{
}

void Model::addIcon(const QString &iconName, const QString &iconPath)
{
    beginInsertRows(QModelIndex(), rowCount(), rowCount());
    if(!indexMap.contains(iconName)) {
        paths.append(iconPath);
        indexMap.insert(iconName,paths.indexOf(iconPath));
    }
    else {

        //Update the icon for the designated icon
        paths[indexMap.value(iconName)] = iconPath;
        QModelIndex index = createIndex(indexMap.value(iconName),1);
        emit dataChanged(index,index);
    }

    endInsertRows();
}

QVariant Model::data(const QModelIndex &index, int role) const
{
    if (index.row() < 0 || index.row() >= indexMap.count())
        return QVariant();

    return paths.at(index.row());
}

int Model::rowCount(const QModelIndex &parent) const
{
    Q_UNUSED(parent)
    return paths.count();
}

QHash<int, QByteArray> Model::roleNames() const
{
    QHash<int, QByteArray> roles;
    roles[PathRole] = "iconImage";
    return roles;
}

Model.h

class Model : public QAbstractListModel {
    Q_OBJECT
public:

    enum MyRoles {
        PathRole = Qt::UserRole + 1
    };
    Q_ENUM(MyRoles)


    explicit Model(QObject *parent = 0);


    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const;
    int rowCount(const QModelIndex &parent = QModelIndex()) const;
    QHash<int, QByteArray> roleNames() const;

    void addIcon(const QString &iconName, const QString &iconPath);

private:
    QList<QString> paths;
    QMap<QString,int> indexMap;

};

包装器：

Q_PROPERTY（MyModel * modelProperty READ getModel NOTIFY modelChanged）

Qml：

import QtQuick 2.5

Rectangle{
width:100
height:30

    ListView{
        id:icons

        property alias myModel: myService.modelProperty

        anchors.fill: parent
        anchors.topMargin: 10
        anchors.rightMargin: 20

        model: myModel

        delegate: Image{source: iconImage}
    }
}

当我第一次设置图标时，它没有任何错误信息。在第一次分配后，出现错误“无法将[undefined]分配给QUrl”。

我在模型中使用addIcon方法添加了新的图标路径。

您知道为什么会发生这种情况吗？

谢谢。

Answer 1

警告表示您从data返回了无效值。

#include <QAbstractListModel>

#define Invalid -1

class Model : public QAbstractListModel
{
    Q_OBJECT
public:
    struct Icon {
        QString name;
        QString path;
    };
    Q_INVOKABLE void add(QString name, QString path) {
        add({name, path});
    }
    void add(const Icon& icon) {
        const int& i = find(icon.name);
        if(i != Invalid) {
            mIconPaths[i].path = icon.path;
            emit dataChanged(index(i), index(i)); // Do not add beginInsertRows
        } else {
            beginInsertRows(QModelIndex(), rowCount(), rowCount());
            mIconPaths.push_back(icon);
            endInsertRows();
        }
    }

    int find(const QString& name) {
        for(int i = 0; i < mIconPaths.size(); i++)
            if(mIconPaths[i].name == name)
                return i;
        return Invalid;
    }

    QVariant data(const QModelIndex &index, int role) const
    {
        Q_UNUSED(role)
        if (index.row() < 0 || index.row() >= rowCount())
            return QVariant();
        return mIconPaths.at(index.row()).path;
    }

    int rowCount(const QModelIndex &parent = QModelIndex()) const
    {
        Q_UNUSED(parent)
        return mIconPaths.count();
    }

    QHash<int, QByteArray> roleNames() const
    {
        QHash<int, QByteArray> roles;
        roles[0] = "icon";
        return roles;
    }

private:
    QList<Icon> mIconPaths;
};

测试QML：

Window
{
    visible: true
    height: 640
    width: 480

    ListView {
        anchors.fill: parent
        model: myModel
        delegate: Text{
            text: icon
        }
        Component.onCompleted: {
            myModel.add("test", "test")
            myModel.add("test", "modified")
            myModel.add("test2", "added")
        }
    }
}

无法将[undefined]分配给QUrl

1 个答案: