的QML查看器(4.8和5.0)被实现这样的:为什么我们需要一个“朋友”在这里? (C++)
在.H(EADER),我们有:
class QtQuick2ApplicationViewer : public QQuickView
{
Q_OBJECT
...
private:
class QtQuick2ApplicationViewerPrivate *d;
};
然后在.CPP文件:
class QtQuick2ApplicationViewerPrivate
{
QString mainQmlFile;
friend class QtQuick2ApplicationViewer;
static QString adjustPath(const QString &path);
};
QtQuick2ApplicationViewer::QtQuick2ApplicationViewer(QWindow *parent)
: QQuickView(parent)
, d(new QtQuick2ApplicationViewerPrivate())
{
connect(engine(), SIGNAL(quit()), SLOT(close()));
setResizeMode(QQuickView::SizeRootObjectToView);
#ifdef Q_OS_ANDROID
engine()->setBaseUrl(QUrl::fromLocalFile("/"));
#endif
}
为什么在这里需要使用friend
?我没有看到任何人会使用friend
类的理由。朋友课程是否有真正的用途(除了那些没有任何人可以生活的外国人)?
.H 的#include
class QtQuick2ApplicationViewer : public QQuickView
{
Q_OBJECT
public:
explicit QtQuick2ApplicationViewer(QWindow *parent = 0);
virtual ~QtQuick2ApplicationViewer();
void setMainQmlFile(const QString &file);
void addImportPath(const QString &path);
void showExpanded();
private:
class QtQuick2ApplicationViewerPrivate *d;
};
的.cpp
#include "qtquick2applicationviewer.h"
#include <QtCore/QCoreApplication>
#include <QtCore/QDir>
#include <QtQml/QQmlEngine>
class QtQuick2ApplicationViewerPrivate
{
QString mainQmlFile;
friend class QtQuick2ApplicationViewer;
static QString adjustPath(const QString &path);
};
QString QtQuick2ApplicationViewerPrivate::adjustPath(const QString &path)
{
#ifdef Q_OS_UNIX
#ifdef Q_OS_MAC
if (!QDir::isAbsolutePath(path))
return QString::fromLatin1("%1/../Resources/%2")
.arg(QCoreApplication::applicationDirPath(), path);
#elif !defined(Q_OS_ANDROID)
const QString pathInInstallDir =
QString::fromLatin1("%1/../%2").arg(QCoreApplication::applicationDirPath(), path);
if (QFileInfo(pathInInstallDir).exists())
return pathInInstallDir;
#endif
#endif
return path;
}
QtQuick2ApplicationViewer::QtQuick2ApplicationViewer(QWindow *parent)
: QQuickView(parent)
, d(new QtQuick2ApplicationViewerPrivate())
{
connect(engine(), SIGNAL(quit()), SLOT(close()));
setResizeMode(QQuickView::SizeRootObjectToView);
#ifdef Q_OS_ANDROID
engine()->setBaseUrl(QUrl::fromLocalFile("/"));
#endif
}
QtQuick2ApplicationViewer::~QtQuick2ApplicationViewer()
{
delete d;
}
void QtQuick2ApplicationViewer::setMainQmlFile(const QString &file)
{
d->mainQmlFile = QtQuick2ApplicationViewerPrivate::adjustPath(file);
setSource(QUrl::fromLocalFile(d->mainQmlFile));
}
void QtQuick2ApplicationViewer::addImportPath(const QString &path)
{
engine()->addImportPath(QtQuick2ApplicationViewerPrivate::adjustPath(path));
}
void QtQuick2ApplicationViewer::showExpanded()
{
#if defined(Q_WS_SIMULATOR)
showFullScreen();
#else
show();
#endif
}
你在这里有两个完全不相关的问题。请不要这样做。每个问题发布一个问题,以及问题。 (即你应该编辑你的帖子,只留下其中一个问题。) – Mat