Qt 获取文件图标、类型 QFileIconProvider

Qt中获取系统图标、类型是通过QFileIconProvider来实现的，具体如下：

一、Qt获取系统文件图标

1、获取文件夹图标

 QFileIconProvider icon_provider;

 QIcon icon = icon_provider.icon(QFileIconProvider::Folder);

 

2、获取指定文件图标

QFileInfo file_info(name);
QFileIconProvider icon_provider;
QIcon icon = icon_provider.icon(file_info);

 

二、Windows编程中获取系统图标、类型：

QIcon Setting::getFileIcon(QString file_name)
{
 QIcon file_icon = QIcon(":/icon/file");
 if(!file_name.isEmpty())
 {
  //获取后缀
  std::string str = "file";
  int index = file_name.lastIndexOf(".");
  if(index >= 0)
  {
   QString suffix = file_name.mid(index); 

   //将QString转化为std::string
   str = suffix.toUtf8().constData(); //std::string((const char *)path.toLocal8Bit())  path.toLatin1().data();
  }

  LPCSTR name = str.c_str();

  
  SHFILEINFOA info;
  if(SHGetFileInfoA(name,
   FILE_ATTRIBUTE_NORMAL,
   &info,
   sizeof(info),
   SHGFI_SYSICONINDEX | SHGFI_ICON | SHGFI_USEFILEATTRIBUTES))
  {
   HICON icon = info.hIcon;
   file_icon = QIcon(QPixmap::fromWinHICON(icon));
  }
 }

 return file_icon;
}

 

QString Setting::getFileType(QString file_name)
{
 QString file_type = QString("file");
 if(!file_name.isEmpty())
 {
  //获取后缀
  std::string str = "file";
  int index = file_name.lastIndexOf(".");
  if(index >= 0)
  {
   QString suffix = file_name.mid(index); 

   //将QString转化为std::string
   str = suffix.toUtf8().constData();
  }

  LPCSTR name = str.c_str();

  
  SHFILEINFOA info;
  if(SHGetFileInfoA(name,
   FILE_ATTRIBUTE_NORMAL,
   &info,
   sizeof(info),
   SHGFI_TYPENAME | SHGFI_USEFILEATTRIBUTES))
  {
   std::string type = info.szTypeName;
   file_type = type.c_str();
  }
 }

 return file_type;
}

 

QIcon Setting::getFolderIcon()
{
 QIcon folder_icon = QIcon(":/icon/folder");

 //将QString转化为std::string
 std::string str = "folder";
 LPCSTR name = str.c_str();

 
 SHFILEINFOA info;
 if(SHGetFileInfoA(name,
  FILE_ATTRIBUTE_DIRECTORY,
  &info,
  sizeof(info),
  SHGFI_SYSICONINDEX | SHGFI_ICON | SHGFI_USEFILEATTRIBUTES))
 {
  HICON h_icon = info.hIcon;

  folder_icon = QIcon(QPixmap::fromWinHICON(h_icon)); 
 }

 return folder_icon;
}

 

QString Setting::getFolderType()
{
 QString folder_type = QString("folder");
 std::string str = "folder";
 LPCSTR name = str.c_str();

 
 SHFILEINFOA info;
 if(SHGetFileInfoA(name,
  FILE_ATTRIBUTE_DIRECTORY,
  &info,
  sizeof(info),
  SHGFI_TYPENAME | SHGFI_USEFILEATTRIBUTES))
 {
  std::string type = info.szTypeName;
  folder_type = type.c_str();
 }

 return folder_type;
}

两种方式最大的区别是什么呢？参考：filesystems - Qt 4.8 - QFileIconProvider, Getting icon for non-existent file (based on extension) - Stack Overflow 诸如所言，Qt所提供的获取图标的方法是本地已存在的文件，如果要通过扩展名来获取图标则需要自己来虚拟构造本地文件，而在数据量较大的情况下往往会影响性能。这（通过扩展名获取图标、类型）可以通过Windows API来实现，即方法二。

Qt5开始QPixmap::fromWinHICON(HICON)已经消失得无影无踪，且获取图标、后缀的方法仍针对本地已存在的文件，那么，只能另寻出路，此节讲述如何通过扩展名来创建临时文件，并获取对应的图标、类型。

步骤：

通过扩展名extension（.***）构造临时文件QTemporaryFile

通过QFileIconProvider获取对应的图标、类型

删除临时文件

获取图标

QIcon FileIcon::fileExtensionIcon(const QString & extension) const 
{
QFileIconProvider icon_provider;
QIcon icon;
QTemporaryFile tmp_file(QDir::tempPath() + QDir::separator() +
QCoreApplication::applicationName() + "_XXXXXX" + extension);
tmp_file.setAutoRemove(false);

if(tmp_file.open()) 
{
QString file_name = tmp_file.fileName();
tmp_file.write(QByteArray());
tmp_file.close();

icon = icon_provider.icon(QFileInfo(file_name));
tmp_file.remove();
} 
else 
{
qCritical()<<QString("failed to write temporary file %1") .arg(tmp_file.fileName());
}

return icon;
}

获取类型

QString FileIcon::fileExtensionType(const QString & extension) const 
{
QFileIconProvider icon_provider;
QString type;
QTemporaryFile tmp_file(QDir::tempPath() + QDir::separator() +
QCoreApplication::applicationName() + "_XXXXXX" + extension);
tmp_file.setAutoRemove(false);

if(tmp_file.open()) 
{
QString file_name = tmp_file.fileName();
tmp_file.write(QByteArray());
tmp_file.close();

type = icon_provider.type(QFileInfo(file_name));

tmp_file.remove();
} 
else 
{
qCritical()<<QString("failed to write temporary file %1") .arg(tmp_file.fileName());
}

return type; 
}