线程的信号是自动发出的。你永远不应该手动发出它们。
您正在尝试使用预处理器来处理代码的两种变体：在 gui 线程或专用线程中处理。Qt 提供了一种非常简单的方法来处理它。
在派生自QObject. event()如果通过发布事件而不是调用槽更容易开始处理，您也可以在重新实现的方法中执行此操作。
如果您希望对象的槽在不同的线程中运行，请使用该moveToThread()方法。
您不需要派生自QThread. 它的默认实现run()自旋一个本地事件循环。
如果您希望您的对象与 GUI 线程中的生活兼容，它必须以小块进行处理并放弃控制，以便 GUI 不会停止。
下面是一个完整的示例，演示了如何在 GUI 或单独的线程中启动工作对象，以及如何在线程之间安全地移动它。
// https://github.com/KubaO/stackoverflown/tree/master/questions/qobject-thread-18653347
#include <QtGui>
#if QT_VERSION >= QT_VERSION_CHECK(5,0,0)
#include <QtWidgets>
#endif
/// See http://stackoverflow.com/a/40382821/1329652
bool isSafe(QObject * obj) {
Q_ASSERT(obj->thread() || qApp && qApp->thread() == QThread::currentThread());
auto thread = obj->thread() ? obj->thread() : qApp->thread();
return thread == QThread::currentThread();
}
class Helper : private QThread {
public:
using QThread::usleep;
};
class Worker : public QObject {
Q_OBJECT
int m_counter;
QBasicTimer m_timer;
void timerEvent(QTimerEvent * ev) override;
public:
Worker(QObject *parent = nullptr) : QObject(parent) {}
/// This method is thread-safe.
Q_SLOT void start() {
if (!isSafe(this)) return (void)QMetaObject::invokeMethod(this, "start");
if (m_timer.isActive()) return;
m_counter = 0;
m_timer.start(0, this);
}
/// This method is thread-safe.
Q_INVOKABLE void startInThread(QObject *targetThread) {
if (!isSafe(this)) return (void)QMetaObject::invokeMethod(this, "startInThread", Q_ARG(QObject*, targetThread));
QObject::moveToThread(qobject_cast<QThread*>(targetThread));
start();
}
Q_SIGNAL void done();
Q_SIGNAL void progress(int percent, bool inGuiThread);
};
void Worker::timerEvent(QTimerEvent * ev)
{
const int busyTime = 50; // [ms] - longest amount of time to stay busy
const int testFactor = 128; // number of iterations between time tests
const int maxCounter = 30000;
if (ev->timerId() != m_timer.timerId()) return;
const auto inGuiThread = []{ return QThread::currentThread() == qApp->thread(); };
QElapsedTimer t;
t.start();
while (1) {
// do some "work"
Helper::usleep(100);
m_counter ++;
// exit when the work is done
if (m_counter > maxCounter) {
emit progress(100, inGuiThread());
emit done();
m_timer.stop();
break;
}
// exit when we're done with a timed "chunk" of work
// Note: QElapsedTimer::elapsed() may be expensive, so we call it once every testFactor iterations
if ((m_counter % testFactor) == 0 && t.elapsed() > busyTime) {
emit progress(m_counter*100/maxCounter, inGuiThread());
break;
}
}
}
class Window : public QWidget {
Q_OBJECT
QVBoxLayout m_layout{this};
QPushButton m_startGUI{"Start in GUI Thread"};
QPushButton m_startWorker{"Start in Worker Thread"};
QLabel m_label;
QThread m_thread{this};
Worker m_worker;
Q_SLOT void showProgress(int p, bool inGuiThread) {
m_label.setText(QString("%1 % in %2 thread")
.arg(p).arg(inGuiThread ? "gui" : "worker"));
}
Q_SLOT void on_startGUI_clicked() {
m_worker.startInThread(qApp->thread());
}
Q_SLOT void on_startWorker_clicked() {
m_worker.startInThread(&m_thread);
}
public:
Window(QWidget *parent = {}, Qt::WindowFlags f = {}) : QWidget(parent, f) {
m_layout.addWidget(&m_startGUI);
m_layout.addWidget(&m_startWorker);
m_layout.addWidget(&m_label);
m_thread.start();
connect(&m_worker, SIGNAL(progress(int,bool)), SLOT(showProgress(int,bool)));
connect(&m_startGUI, SIGNAL(clicked(bool)), SLOT(on_startGUI_clicked()));
connect(&m_startWorker, SIGNAL(clicked(bool)), SLOT(on_startWorker_clicked()));
}
~Window() {
m_thread.quit();
m_thread.wait();
}
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Window w;
w.show();
return a.exec();
}
#include "main.moc"