您正在阻止您的 GUI 线程，因此重绘将不起作用，这显然是糟糕的设计。你永远不应该阻止 GUI 线程。
如果你坚持在 GUI 线程中做工作，你必须强行将工作切成小块，并在每个块之后返回主事件循环。嵌套事件循环是邪恶的，所以甚至不要认为你想要一个。所有这些都带有不好的代码气味，所以请远离。
或者，只需将您的计算QObject移至工作线程并在那里完成工作。
下面的代码演示了这两种技术。很容易注意到，工作分割需要在工作对象内部保持循环状态，而不仅仅是在循环中本地。它更混乱，代码闻起来很糟糕，再次 - 避免它。
该代码适用于 Qt 4.8 和 5.1。
//main.cpp
#include <QApplication>
#include <QThread>
#include <QWidget>
#include <QBasicTimer>
#include <QElapsedTimer>
#include <QGridLayout>
#include <QPlainTextEdit>
#include <QPushButton>
class Helper : private QThread {
public:
using QThread::usleep;
};
class Trainer : public QObject {
Q_OBJECT
Q_PROPERTY(float stopMSE READ stopMSE WRITE setStopMSE)
float m_stopMSE;
int m_epochCounter;
QBasicTimer m_timer;
void timerEvent(QTimerEvent * ev);
public:
Trainer(QObject *parent = 0) : QObject(parent), m_stopMSE(1.0) {}
Q_SLOT void startTraining() {
m_epochCounter = 0;
m_timer.start(0, this);
}
Q_SLOT void moveToGUIThread() { moveToThread(qApp->thread()); }
Q_SIGNAL void hasNews(const QString &);
float stopMSE() const { return m_stopMSE; }
void setStopMSE(float m) { m_stopMSE = m; }
};
void Trainer::timerEvent(QTimerEvent * ev)
{
const int updateTime = 50; //ms
const int maxEpochs = 5000000;
if (ev->timerId() != m_timer.timerId()) return;
QElapsedTimer t;
t.start();
while (1) {
// do the work here
float currentMSE;
#if 0
for (int i=0; i<zbior_uczacy_rozmiary[0]; i++) { //internal loop of training
alg_bp(zbior_uczacy[i], &zbior_uczacy[i][zbior_uczacy_rozmiary[1]]);
currentMSE += licz_mse(&zbior_uczacy[i][zbior_uczacy_rozmiary[1]]);
}
#else
Helper::usleep(100); // pretend we're busy doing some work
currentMSE = 2E4/m_epochCounter;
#endif
// bail out if we're done
if (currentMSE <= m_stopMSE || m_epochCounter >= maxEpochs) {
QString s = QString::fromUtf8("Zakończono uczenie po %1 epokach, osiągając MSE: %2")
.arg(m_epochCounter).arg(currentMSE);
emit hasNews(s);
m_timer.stop();
break;
}
// send out periodic updates
// Note: QElapsedTimer::elapsed() may be expensive, so we don't call it all the time
if ((m_epochCounter % 128) == 1 && t.elapsed() > updateTime) {
QString s = QString::fromUtf8("Uczenie w toku, po %1 epokach MSE wynosi: %2")
.arg(m_epochCounter).arg(currentMSE);
emit hasNews(s);
// return to the event loop if we're in the GUI thread
if (QThread::currentThread() == qApp->thread()) break; else t.restart();
}
m_epochCounter++;
}
}
class Window : public QWidget {
Q_OBJECT
QPlainTextEdit *m_log;
QThread *m_worker;
Trainer *m_trainer;
Q_SIGNAL void startTraining();
Q_SLOT void showNews(const QString & s) { m_log->appendPlainText(s); }
Q_SLOT void on_startGUI_clicked() {
QMetaObject::invokeMethod(m_trainer, "moveToGUIThread");
emit startTraining();
}
Q_SLOT void on_startWorker_clicked() {
m_trainer->moveToThread(m_worker);
emit startTraining();
}
public:
Window(QWidget *parent = 0, Qt::WindowFlags f = 0) :
QWidget(parent, f), m_log(new QPlainTextEdit), m_worker(new QThread(this)), m_trainer(new Trainer)
{
QGridLayout * l = new QGridLayout(this);
QPushButton * btn;
btn = new QPushButton("Start in GUI Thread");
btn->setObjectName("startGUI");
l->addWidget(btn, 0, 0, 1, 1);
btn = new QPushButton("Start in Worker Thread");
btn->setObjectName("startWorker");
l->addWidget(btn, 0, 1, 1, 1);
l->addWidget(m_log, 1, 0, 1, 2);
connect(m_trainer, SIGNAL(hasNews(QString)), SLOT(showNews(QString)));
m_trainer->connect(this, SIGNAL(startTraining()), SLOT(startTraining()));
m_worker->start();
QMetaObject::connectSlotsByName(this);
}
~Window() {
m_worker->quit();
m_worker->wait();
delete m_trainer;
}
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Window w;
w.show();
return a.exec();
}
#include "main.moc"