除了使用项目角色之外，如何以QML（通过委托）访问存储在QAbstractListmodel中的项目？

1 回答

• 8

  您可以使用一个特殊角色来返回整个项目，如下所示：

  template<typename T>
  class List : public QAbstractListModel
  {
  public:
    explicit List(const QString &itemRoleName, QObject *parent = 0)
      : QAbstractListModel(parent)
    {
      QHash<int, QByteArray> roles;
      roles[Qt::UserRole] = QByteArray(itemRoleName.toAscii());
      setRoleNames(roles);
    }
  
    void insert(int where, T *item) {
      Q_ASSERT(item);
      if (!item) return;
      // This is very important to prevent items to be garbage collected in JS!!!
      QDeclarativeEngine::setObjectOwnership(item, QDeclarativeEngine::CppOwnership);
      item->setParent(this);
      beginInsertRows(QModelIndex(), where, where);
      items_.insert(where, item);
      endInsertRows();
    }
  
  public: // QAbstractItemModel
    int rowCount(const QModelIndex &parent = QModelIndex()) const {
      Q_UNUSED(parent);
      return items_.count();
    }
  
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const {
      if (index.row() < 0 || index.row() >= items_.count()) {
        return QVariant();
      }
      if (Qt::UserRole == role) {
        QObject *item = items_[index.row()];
        return QVariant::fromValue(item);
      }
      return QVariant();
    }
  
  protected:
    QList<T*> items_;
  };
  

  不要忘记在所有插入方法中使用QDeclarativeEngine::setObjectOwnership . 否则，从数据方法返回的所有对象都将在QML端进行垃圾收集 .

  回复于 2024-05-16T18:36:17+08:00