Question

当时我一直在为此而努力。

Qt sQFileSystemModel, 因为在计算几百份档案时确实很慢,因为icon fetching算法确实坏。

我想说的是完全可以置信的讽刺。页: 1 QFileSystemModel:datameth which is not actual (the source of QFileSystemModel is available here:

This is the code I m trying to run:

class FileModel : public QFileSystemModel {
    using QFileSystemModel::data;
public:
    QVariant QFileSystemModel::data(const QModelIndex &index, int role) const
    {
     // my own implementation here
    }
}

但它失败了。

<条码> 成员职能的定义 QFileSystemModel:data witin fileModel

<>>>>>

我设法压倒了这一职能,这是我现在的事情:

class FileModel : public QFileSystemModel {
public:
    QVariant data(const QModelIndex &index, int role) const
    {
    // Here goes Qt s implementation
    Q_D(const QFileSystemModel);
    if (!index.isValid() || index.model() != this)
        return QVariant();
    switch (role) {
    case Qt::EditRole:
    case Qt::DisplayRole:
        switch (index.column()) {
        case 0: return d->name(index);
        case 1: return d->size(index);
        case 2: return d->type(index);
        case 3: return d->time(index);
        default:
            qWarning("data: invalid display value column %d", index.column());
            break;
        }
        break;
    case FilePathRole:
        return filePath(index);
    case FileNameRole:
        return d->name(index);
    case Qt::DecorationRole:
        if (index.column() == 0) {
            QIcon icon = d->icon(index); // This is the part I need to change
            if (icon.isNull()) {
                if (d->node(index)->isDir())
                    icon = d->fileInfoGatherer.iconProvider()->icon(QFileIconProvider::Folder);
                else
                    icon = d->fileInfoGatherer.iconProvider()->icon(QFileIconProvider::File);
            }
            return icon;
        }
        break;
    case Qt::TextAlignmentRole:
        if (index.column() == 1)
            return Qt::AlignRight;
        break;
    case FilePermissions:
        int p = permissions(index);
        return p;
    }
    return QVariant();
}
};

However this code doesn t compile. This is the error I get: const QFileSystemModelPrivate* QFileSystemModel::d_func() const is private

Answer 1

预计会出现这样的情况,因为有办法确定“提供方”:

参数,即<条码>QFileIconProvider,被视为一种非常简单的类别,可采用一种方法,从<条码>QFileInfo(主要为档案名称):

rel=“nofollow”http://doc.qt.io/archives/qt.7/qfileinfo.html

You could implement one of these that just returns the same icon for everything. If you find that doesn t address your problem, the following compiled fine for me...FWIW:

class FileModel : public QFileSystemModel {
public:
    QVariant data(const QModelIndex &index, int role) const
    {
        if (role == Qt::DecorationRole) {
            return QVariant (QIcon ());
        }    

        return QFileSystemModel::data(index, role);
    }
};

Answer 2

如果一个基类的功能是虚拟的,那么该功能在衍生类别中也是虚拟的。下面将印刷“C”:

#include <iostream>

class A {
public:
  virtual void data() = 0;
};

class B: public A {
public:
  void data() { std::cout << "B
"; }
};

class C: public B {
public:
  void data() { std::cout << "C
"; }
};

int
main() {
  C c;
  A *a = &c;
  a->data();

  return 0;
}

<代码>QFileSystemDialog源自QAbstractItemModel,其中data(<>纯属虚拟。即便是,如果它本身执行,它就没有超过<条码>数据()。

见。

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