如何覆盖（重新实现）QFileSystemModel中的成员函数 [英] How to override (re-implement) a member function in QFileSystemModel

问题描述

我一直在努力这一段时间。

Qt的 QFileSystemModel 因为一个非常糟糕的图标提取算法。

我想完全禁用图标。它们在 QFileSystemModel :: data 方法中获取，它不是虚拟的（QFileSystemModel的源在这里可用： http://qt.gitorious.org/qt/qt/blobs/4.7/src/gui/dialogs/qfilesystemmodel。 cpp ）

这是我试图运行的代码：

  class FileModel：public QFileSystemModel {
 using QFileSystemModel :: data; 
 public：
 QVariant QFileSystemModel :: data（const QModelIndex& index，int role）const 
 {
 //我自己实现这里
} 
 } 
  

但是失败

code>无法定义成员函数QFileSystemModel :: data FileModel

UPDATE b
$ b

我已经设法覆盖该函数，这是我现在的：

  class FileModel：public QFileSystemModel {
 public：
 QVariant数据（const QModelIndex& index，int role）const 
 {
 //这里Qt的实现
 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）; 
默认值：
 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）; //这是我需要改变的部分
 if（icon.isNull（））{
 if（d-> node（index） - > isDir（））
 icon = d-> fileInfoGatherer.iconProvider（） - >图标（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（）; 
} 
}; 
  

但是这个代码不能编译。这是我得到的错误：
'const QFileSystemModelPrivate * QFileSystemModel :: d_func（）const'是私人的

解决方案

看起来是这样的，因为有一个方法来设置图标提供者：

http://doc.qt.io/archives/qt-4.7/qfilesystemmodel.html# setIconProvider

参数， QFileIconProvider 看起来是一个相当简单的类，一个自己的实例，使用从 QFileInfo （基本上，文件名）获取图标的方法：

http://doc.qt.io/archives/qt-4.7/qfileinfo。 html

您可以实现其中之一，只为所有内容返回相同的图标。如果你发现没有解决你的问题，以下编译的罚款为我... 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）; 
} 
}; 
  

I've been struggling with this for a while.

Qt's QFileSystemModel is really slow when fetching several hundred files because of a really bad icon fetching algorithm.

I want to completely disable icons. They are fetched in QFileSystemModel::data method which is not virtual (the source of QFileSystemModel is available here: http://qt.gitorious.org/qt/qt/blobs/4.7/src/gui/dialogs/qfilesystemmodel.cpp)

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
    }
}

but it fails with

cannot define member function QFileSystemModel::data witin FileModel

UPDATE

I've managed to override the function and this is what I have now:

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

解决方案

Looks like this was anticipated, as there is a method for setting the "icon provider":

http://doc.qt.io/archives/qt-4.7/qfilesystemmodel.html#setIconProvider

The parameter, a QFileIconProvider, looks to be a fairly simple class that you can implement an instance of yourself, with a method that fetches an icon from a QFileInfo (basically, a file name):

http://doc.qt.io/archives/qt-4.7/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);
    }
};

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