Qt从GUI线程停止工作线程循环

Question

i have a worker thread which i try to stop through a button. i sometimes get the following error:

Fatal: QThread: Destroyed while thread is still running

Here is my code. By pushing the disconnect button a signal is emitted to stop the thread's while loop.

if (ui->connectButton->text() == "Connect") {
    mUDPThread = new QThread;
    mUDPWorker = new  UDPThread(ui->HostTextEdit->toPlainText(), ui->portTextEdit->toPlainText().toInt());
    mUDPWorker->moveToThread(mUDPThread);
    connect(mUDPThread, SIGNAL(started()), mUDPWorker, SLOT(process()));
    connect(mUDPWorker, SIGNAL(finished()), mUDPThread, SLOT(quit()));
    connect(mUDPWorker, SIGNAL(finished()), mUDPWorker, SLOT(deleteLater()));
    connect(mUDPWorker, SIGNAL(finished()), mUDPThread, SLOT(deleteLater()));
    connect(this, SIGNAL(onExitThread()), mUDPWorker, SLOT(onExitThread()));
    connect(this, SIGNAL(onDataIncome(QString)), mUDPWorker, SLOT(onDataIncome(QString)));
    mUDPThread->start();
    ui->connectButton->setText("Disconnect");
} else if (ui->connectButton->text() == "Disconnect") {
    emit onExitThread();
    ui->connectButton->setText("Connect");
}

the worker Thread:

void UDPThread::process() {
    while (isRunning) {
    QCoreApplication::processEvents();
      ...
    }
    emit finished();
}
void UDPThread::onExitThread() {
    qDebug() << "onExitThread" << isRunning;
    isRunning = false;
}

Answer 1

while (isRunning)

You are blocking the thread right there, its event loop cannot spin in order to receive signals, it can only send signals to other threads with spinning event loops.

You need to make your worker non-blocking, split the work in cycles, in between the event loop gets to spin and receive signals. In pseudocode:

if (isRunning) {
  doWorkCycle();
  scheduleNextWorkCycle();
} else emit finished();

There is an example you can look at here .

Answer 2

Solved it. The error was within the connect commands:

connect(mUDPWorker, SIGNAL(finished()), mUDPThread, SLOT(deleteLater()));

to

connect(mUDPThread, SIGNAL(finished()), mUDPThread, SLOT(deleteLater()));

result:

connect(mUDPThread, SIGNAL(started()), mUDPWorker, SLOT(process()));
connect(mUDPWorker, SIGNAL(finished()), mUDPThread, SLOT(quit()));
connect(mUDPWorker, SIGNAL(finished()), mUDPWorker, SLOT(deleteLater()));
connect(mUDPThread, SIGNAL(finished()), mUDPThread, SLOT(deleteLater()));
connect(this, SIGNAL(onExitThread()), mUDPWorker, SLOT(onExitThread()));
connect(this, SIGNAL(onDataIncome(QString)), mUDPWorker, SLOT(onDataIncome(QString)));