让任意线程执行一个匿名函数

Posted 2020-07-02 朝闻道

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本类主要功能是在当前线程（比如说主线程），指派任意一个线程（比如说某个工作线程）去执行一个匿名函数。

注意，这个和QtConcurrent配合QThreadPool不一样，QtConcurrent配合QThreadPool只能指派回调到QThreadPool中的线程。

而这个类可以指派一个回调到任意线程。

两个主要接口

JasonQt_InvokeFromThread::invoke：非阻塞，只是将回调放到队列中，等待执行

JasonQt_InvokeFromThread::waitForInvoke：阻塞，函数执行完成后才回返回

代码部分：

.h文件内容：

[cpp] view plain copy

#include <QThread>
#include <QMap>
#include <QDebug>
class JasonQt_InvokeFromThreadHelper: public QObject
{
Q_OBJECT
private:
QMutex m_mutex;
QList< std::function<void()> > m_waitCallbacks;
public:
void addCallback(const std::function<void()> &callback);
public slots:
void onRun();
};
class JasonQt_InvokeFromThread
{
private:
static QMutex g_mutex;
static QMap< QThread *, JasonQt_InvokeFromThreadHelper * > g_helpers;
public:
static void invoke(QThread *thread, const std::function<void()> &callback);
static void waitForInvoke(QThread *thread, const std::function<void()> &callback);
};

.cpp文件内容

[cpp] view plain copy

// JasonQt_InvokeFromThreadHelper
void JasonQt_InvokeFromThreadHelper::addCallback(const std::function<void ()> &callback)
{
m_mutex.lock();
m_waitCallbacks.push_back(callback);
m_mutex.unlock();
}
void JasonQt_InvokeFromThreadHelper::onRun()
{
if(!m_waitCallbacks.isEmpty())
{
m_mutex.lock();
auto callback = m_waitCallbacks.first();
m_waitCallbacks.pop_front();
m_mutex.unlock();
callback();
}
}
// JasonQt_InvokeFromThread
QMutex JasonQt_InvokeFromThread::g_mutex;
QMap< QThread *, JasonQt_InvokeFromThreadHelper * > JasonQt_InvokeFromThread::g_helpers;
void JasonQt_InvokeFromThread::invoke(QThread *thread, const std::function<void ()> &callback)
{
if(!(thread->isRunning()))
{
qDebug() << "JasonQt_InvokeFromThread::invoke: Target thread" << thread << "is not running!";
return;
}
g_mutex.lock();
auto it = g_helpers.find(thread);
if(it == g_helpers.end())
{
auto helper = new JasonQt_InvokeFromThreadHelper;
helper->moveToThread(thread);
QObject::connect(thread, &QThread::finished, [=]()
{
g_mutex.lock();
auto it = g_helpers.find(thread);
if(it != g_helpers.end())
{
g_helpers.erase(it);
}
g_mutex.unlock();
});
g_helpers.insert( thread, helper );
it = g_helpers.find(thread);
}
it.value()->addCallback(callback);
QMetaObject::invokeMethod(it.value(), "onRun", Qt::QueuedConnection);
g_mutex.unlock();
}
void JasonQt_InvokeFromThread::waitForInvoke(QThread *thread, const std::function<void ()> &callback)
{
if(!(thread->isRunning()))
{
qDebug() << "JasonQt_InvokeFromThread::waitForInvoke: Target thread" << thread << "is not running!";
return;
}
g_mutex.lock();
auto it = g_helpers.find(thread);
if(it == g_helpers.end())
{
auto helper = new JasonQt_InvokeFromThreadHelper;
helper->moveToThread(thread);
QObject::connect(thread, &QThread::finished, [=]()
{
g_mutex.lock();
auto it = g_helpers.find(thread);
if(it != g_helpers.end())
{
g_helpers.erase(it);
}
g_mutex.unlock();
});
g_helpers.insert( thread, helper );
it = g_helpers.find(thread);
}
it.value()->addCallback([&]()
{
g_mutex.unlock();
callback();
});
QMetaObject::invokeMethod(it.value(), "onRun", Qt::QueuedConnection);
g_mutex.lock();
g_mutex.unlock();
}