c++ - 将 C++ 模块连接到 QML - ReferenceError : is not defined

Question

我有一个装满相册的数据库，我想在 GridView 中显示这些相册。我创建了一个 qml 文件，该文件采用个性化模块 (albumObject.h)，以便从数据库中获取数据。因为我在 main.cpp 中已经有一个 MainWindow 我需要在构造的 QQuickWidget 中显示 GridView在 mainwindow.cpp 文件中。这是代码:

albumObject.h

class AlbumObject : public QObject {
  Q_OBJECT

  Q_PROPERTY(QString artist READ getArtist)
  Q_PROPERTY(QString album READ getAlbum)
  Q_PROPERTY(QString date READ getDate)
  Q_PROPERTY(QString img READ getImg)

public:
  AlbumObject(QObject* parent = nullptr);

  const QString getArtist() const;
  const QString getAlbum() const;
  const QString getDate() const;
  const QString getImg() const;

  void setArtist(const QString& artist);
  void setAlbum(const QString& album);
  void setDate(const QString& date);
  void setImg(const QString& img);


private:
  QString m_artist;
  QString m_album;
  QString m_date;
  QString m_img;
};

主窗口.cpp

当所有专辑都添加到数据库时，我在 MainWindow 构造函数中使用此连接来更新 UI

  connect(&databaseManager, &DatabaseManager::albumAddedToDB,
          &databaseManager, [&]() {
    QList<QObject*> albums = databaseManager.getAlbumsFromDB();

    QQuickView view;
    view.setResizeMode(QQuickView::SizeRootObjectToView);
    QQmlContext *ctxt = view.rootContext();
    ctxt->setContextProperty("albumModel", QVariant::fromValue(albums));
    ui->albumGrid->setSource(QUrl{"../Hallownest/Model/something.qml"});
    ui->albumGrid->createWindowContainer(&view, this);
  });

something.qml

import QtQuick 2.4

Rectangle {
    width: 800; height: 600

    Component {
        id: albumDelegate
        Item {
            width: grid.cellWidth; height: grid.cellHeight
            Column {
                anchors.fill: parent
                Text { text: artist; anchors.horizontalCenter:  parent.horizontalCenter }
                Text { text: album; anchors.horizontalCenter:  parent.horizontalCenter }
                Text { text: date; anchors.horizontalCenter:  parent.horizontalCenter }
            }
        }
    }

    GridView {
        id: grid
        anchors.fill: parent
        cellWidth: 150; cellHeight: 150

        model: albumModel
        delegate: albumDelegate
        highlight: Rectangle {color: "lightsteelblue"; radius: 5 }
        focus: true;
    }
}

当我启动程序时出现此错误:

ReferenceError: albumModel is not defined

在类似的问题中，大多数用户都有这个问题，因为他们在加载 qml 文件后设置了上下文，但我的情况不是这样。

Answer 1

你的问题是你创建了一个 QQuickView 不必要地认为这样你会得到 QQmlContext 但它是不正确的，QQuikWidget 已经有它自己的 QQmlContext。另一方面，列表最好是一个属性并导出 MainWindow，这样您就可以访问该属性。

*.h

class MainWindow : public QMainWindow
{
    Q_OBJECT
    Q_PROPERTY(QList<QObject *> albums READ getAlbums NOTIFY albumsChanged)

public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
    QList<QObject *> getAlbums() const;
    void updateAlbums();
signals:
    void albumsChanged();
private:
    Ui::MainWindow *ui;
    QList<QObject *> m_albums;
    DatabaseManager databaseManager;
};

*.cpp

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    ui->albumGrid->rootContext()->setContextProperty("mainwindow", this);
    ui->albumGrid->setSource(QUrl{"../Hallownest/Model/something.qml"});
    connect(&databaseManager, &DatabaseManager::albumAddedToDB, this, &MainWindow::updateAlbums);
}

MainWindow::~MainWindow()
{
    delete ui;
}

QList<QObject *> MainWindow::getAlbums() const
{
    return m_albums;
}

void MainWindow::updateAlbums()
{
    qDeleteAll(m_albums);
    m_albums.clear();
    m_albums = databaseManager.getAlbumsFromDB();
    emit albumsChanged();
}

*.qml

import QtQuick 2.4

Rectangle {
    width: 800; height: 600

    Component {
        id: albumDelegate
        Item {
            width: grid.cellWidth; height: grid.cellHeight
            Column {
                anchors.fill: parent
                Text { text: modelData.artist; anchors.horizontalCenter:  parent.horizontalCenter }
                Text { text: modelData.album; anchors.horizontalCenter:  parent.horizontalCenter }
                Text { text: modelData.date; anchors.horizontalCenter:  parent.horizontalCenter }
            }
        }
    }

    GridView {
        id: grid
        anchors.fill: parent
        cellWidth: 150; cellHeight: 150
        model: mainwindow.albums
        delegate: albumDelegate
        highlight: Rectangle {color: "lightsteelblue"; radius: 5 }
        focus: true;
    }
}