如何从 main.cpp 中的 cpp 文件获取函数结果？

Question

我想从 QT 的 main.cpp 中的 c++ 文件中获取函数结果。

例子

.h 文件：

ifndef HOTPLUGWATCHER_GUI_H
#define HOTPLUGWATCHER_GUI_H

#include <QWidget>

class QTextBrowser;
class QSystemTrayIcon;
class QLabel;
class QPushButton;
class QToolButton;
class QDeviceWatcher;
class HotplugWatcher_GUI : public QWidget
{
    Q_OBJECT
public:
    explicit HotplugWatcher_GUI(QWidget *parent = 0);
    ~HotplugWatcher_GUI();

    void appendMessage(const QString& msg);

public slots:
    void toggleWatch();
    void showDetail(bool show);
    void slotDeviceAdded(const QString& dev);
    void slotDeviceRemoved(const QString& dev);
    void slotDeviceChanged(const QString& dev);

private:
    QDeviceWatcher *watcher;

    QLabel *state;
    QTextBrowser *msg_view;
    QPushButton *button;
    QToolButton *detail_button;
    QSystemTrayIcon *tray;
};

#endif // HOTPLUGWATCHER_GUI_H

cpp 文件：

#include "hotplugwatcher_gui.h"

#include <QtCore/QThread>
#include <QVBoxLayout>
#include <QLabel>
#include <QPushButton>
#include <QTextBrowser>
#include <QToolButton>
#include <QSystemTrayIcon>
#include <QMessageBox>

#include "qdevicewatcher.h"

HotplugWatcher_GUI::HotplugWatcher_GUI(QWidget *parent) :
    QWidget(parent)
{
    QVBoxLayout *vbl = new QVBoxLayout(this);
    setLayout(vbl);

    state = new QLabel(this);
    //qDebug()<<state;
    button = new QPushButton(tr("Start"), this);
    detail_button = new QToolButton(this);
    detail_button->setText(tr("Detail"));
    detail_button->setCheckable(true);
    detail_button->setChecked(true);
    msg_view = new QTextBrowser(this);
    msg_view->setLineWrapMode(QTextEdit::NoWrap);

    QHBoxLayout *hbl = new QHBoxLayout(this);
    hbl->addWidget(button);
    hbl->addWidget(detail_button);

    vbl->addWidget(state);
    vbl->addLayout(hbl);
    vbl->addWidget(msg_view);

    tray = new QSystemTrayIcon(this);
    tray->show();

    watcher = new QDeviceWatcher;
    watcher->appendEventReceiver(this);
    connect(watcher, SIGNAL(deviceAdded(QString)), this, SLOT(slotDeviceAdded(QString)), Qt::DirectConnection);
    connect(watcher, SIGNAL(deviceChanged(QString)), this, SLOT(slotDeviceChanged(QString)), Qt::DirectConnection);
    connect(watcher, SIGNAL(deviceRemoved(QString)), this, SLOT(slotDeviceRemoved(QString)), Qt::DirectConnection);

    connect(button, SIGNAL(clicked()), SLOT(toggleWatch()));
    connect(detail_button, SIGNAL(toggled(bool)), SLOT(showDetail(bool)));
}

HotplugWatcher_GUI::~HotplugWatcher_GUI()
{

}

void HotplugWatcher_GUI::appendMessage(const QString &msg)
{
    msg_view->append(msg);
}

void HotplugWatcher_GUI::toggleWatch()
{
    if (watcher->isRunning()) {
        if (!watcher->stop()) {
            QMessageBox::warning(0, tr("WARNGING"), tr("Failed to stop"));
        }
        button->setText(tr("Start"));
    } else {
        if (!watcher->start()) {
            QMessageBox::warning(0, tr("WARNGING"), tr("Failed to start"));
        }
        button->setText(tr("Stop"));
    }
}

void HotplugWatcher_GUI::showDetail(bool show)
{
    msg_view->setVisible(show);
    int w = width();
    adjustSize();  //width changes
    resize(w, height());
}

void HotplugWatcher_GUI::slotDeviceAdded(const QString &dev)
{
    qDebug("tid=%#x: add %s", (quintptr) QThread::currentThreadId(), qPrintable(dev));

    state->setText("<font color=#0000ff>Add: </font>" + dev);
    tray->showMessage(tr("New device"), dev);
}

void HotplugWatcher_GUI::slotDeviceChanged(const QString &dev)
{
    qDebug("tid=%#x: change %s", (quintptr) QThread::currentThreadId(), qPrintable(dev));

    state->setText("<font color=#0000ff>Change: </font>" + dev);
    tray->showMessage(tr("Change device"), dev);
}

void HotplugWatcher_GUI::slotDeviceRemoved(const QString &dev)
{
    qDebug("tid=%#x: remove %s", (quintptr) QThread::currentThreadId(), qPrintable(dev));

    state->setText("<font color=#0000ff>Remove: </font>" + dev);
    tray->showMessage(tr("Remove device"), dev);
}

和main.cpp

#include <QApplication>
#include "hotplugwatcher_gui.h"

static HotplugWatcher_GUI *gui = 0;

#if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
#define qInstallMessageHandler qInstallMsgHandler
void MsgOuput(QtMsgType type, const char *msg)
{
#else
void MsgOuput(QtMsgType type, const QMessageLogContext &, const QString& msg)
{
#endif
    Q_UNUSED(type)
    if (gui)
        gui->appendMessage(msg);
}

int main(int argc, char *argv[])
{
    qInstallMessageHandler(MsgOuput);
    QApplication a(argc, argv);

    HotplugWatcher_GUI hotplug;
    gui = &hotplug;
    hotplug.show();
    return a.exec();
}

所以这个用按钮打开的小部件，当按下“星号”按钮时，当我连接 USB 设备时，我可以在小部件上看到一些信息。

这是一个很好的开始。

但是，我不想拥有小部件，而是将接收到的数据发送到 QML 以使用。

第一个也是主要的问题，我知道调用函数是怎样的：

do_something(2,5)

函数是

int do_something (int arg1,int arg2)
{
    int res = arg1 + arg2
    return res
}

我不知道如何在我的 main.cpp 中从另一个 cpp 文件中的函数获取函数的“状态”结果：

void HotplugWatcher_GUI::slotDeviceAdded(const QString &dev)
{
    qDebug("tid=%#x: add %s", (quintptr) QThread::currentThreadId(), qPrintable(dev));

    state->setText("<font color=#0000ff>Add: </font>" + dev);
    tray->showMessage(tr("New device"), dev);
}

所以如果有人能帮助我理解我将不胜感激

感谢大家的帮助

Answer 1

如果我理解正确，您希望访问类的“状态”成员。

最好的办法是在检索它的类中创建另一个函数。例如：

QLabel* HotplugWatcher_GUI::getState() const
{
   return state;
}

但这有点难看。如果您只对文本感兴趣，那么您可以这样做：

QString HotplugWatcher_GUI::getStateText() const
{
   return state->text();
}