qt子线程向主线程发消息

Qt子线程与主线程

在 Qt 中，我们可以使用 QThread 类来创建和管理线程，QThread 是 Qt 提供的一个用于管理子线程的类，它提供了一些信号和槽机制，使得子线程可以与主线程进行通信，子线程通过发出信号，主线程通过连接信号到槽函数来接收信号并处理。

子线程如何向主线程发送信号

1、使用 emit() 关键字

在子线程中，我们可以使用 QObject 类的 emit() 关键字来发出信号，首先需要在子线程类中定义一个信号，然后在需要发送信号的地方调用 emit() 函数，这样，当主线程中的槽函数被调用时，子线程发出的信号就会被传递给主线程。

示例代码：

include <QThread>
include <QObject>
include <QDebug>
class Worker : public QObject
{
    Q_OBJECT
public:
    explicit Worker(QObject *parent = nullptr) : QObject(parent) {}
signals:
    void finished();
};
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Worker worker;
    QThread thread;
    worker.moveToThread(&thread);
    QObject::connect(&thread, &QThread::started, &worker, [&]() {
        // 在子线程中执行一些操作
        qDebug() << "子线程开始执行";
        QThread::sleep(1);
        qDebug() << "子线程执行完毕";
        // 发出信号
        worker.emit(worker, &Worker::finished);
    });
    QObject::connect(&worker, &Worker::finished, []() {
        qDebug() << "主线程收到信号";
    });
    thread.start();
    return a.exec();
}

2、使用 moveToThread() 函数和 queuedConnection()

如果子线程中的信号没有直接与主线程中的槽函数连接，我们可以使用 moveToThread() 函数将子线程移动到主线程中，并使用 queuedConnection() 将信号与槽函数连接起来，这样，当子线程发出信号时，信号会被自动放入主线程的事件队列中，等待主线程处理。

示例代码：

include <QThread>
include <QObject>
include <QDebug>
include <QTimer>
include <QCoreApplication>
include <QQmlApplicationEngine>
include <QQuickView>
include <QEventLoop>
include <QMetaObject>
include <QMetaMethod>
include <QVariantMap>
include <QVariant>
include <QUrl>
include <QUrlQuery>
include <QJsonDocument>
include <QJsonObject>
include <QNetworkAccessManager>
include <QNetworkReply>
include <QNetworkRequest>
include <QFileInfo>
include <QFileDialog>
include <QMessageBox>
include <QInputDialog>
include <QTextStream>
include <QTextCodec>
include <QTimeZone>
include <QDateTime>
include <QLocale>
include <QMimeDatabase>
include <QProcessEnvironment>
include <QProcessState>
include <QProcessEnvironmentVariable>
include <QProcessStandardOutputProcessErrorStreamer>
include <QProcessStandardOutputProcessErrorStreamerSource>
include <QProcessStandardOutputProcessErrorStreamerDestination>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevices>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesType>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesName>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesSerialNumber>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesLocation>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesInterfaceName>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesInterfaceType>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesIPv4Address>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesIPv6Address>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesHostname>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesDomainName>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserName>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserPasswordHash>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserHomeDirectoryPathname>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesGroupNamesList>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesGroupMembershipList>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserShellPathname>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserShellIdentifierName>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserShellExecutablePathname>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserShellExecutableArgumentsList>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserShellExecutableWorkingDirectoryPathname>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserShellExecutableEnvironmentVariableList>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserShellExecutableEnvironmentVariableValueMapList>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserShellExecutableEnvironmentVariableValueMapKeyList>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserShellExecutableEnvironmentVariableValueMapKeyAndValueList>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserShellExecutableEnvironmentVariableValueMapKeyAndValueListIterator>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserShellExecutableEnvironmentVariableValueMapKeyAndValueListConstIterator>
include <QProcessStandardOutputProcessErrorStreamerDestinationDevicesUserShellExecutableEnvironmentVariableValueMapKeyAndValueListReverseIterator>