让任意线程执行一个匿名函数

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

1. #include <QThread>
2. #include <QMap>
3. #include <QDebug>
4. class JasonQt_InvokeFromThreadHelper: public QObject
5. {
6. Q_OBJECT
7. private:
8. QMutex m_mutex;
9. QList< std::function<void()> > m_waitCallbacks;
10. public:
11. void addCallback(const std::function<void()> &callback);
12. public slots:
13. void onRun();
14. };
15. class JasonQt_InvokeFromThread
16. {
17. private:
18. static QMutex g_mutex;
19. static QMap< QThread *, JasonQt_InvokeFromThreadHelper * > g_helpers;
20. public:
21. static void invoke(QThread *thread, const std::function<void()> &callback);
22. static void waitForInvoke(QThread *thread, const std::function<void()> &callback);
23. };

.cpp文件内容

[cpp] view plain copy

1. // JasonQt_InvokeFromThreadHelper
2. void JasonQt_InvokeFromThreadHelper::addCallback(const std::function<void ()> &callback)
3. {
4. m_mutex.lock();
5. m_waitCallbacks.push_back(callback);
6. m_mutex.unlock();
7. }
8. void JasonQt_InvokeFromThreadHelper::onRun()
9. {
10. if(!m_waitCallbacks.isEmpty())
11. {
12. m_mutex.lock();
13. auto callback = m_waitCallbacks.first();
14. m_waitCallbacks.pop_front();
15. m_mutex.unlock();
16. callback();
17. }
18. }
19. // JasonQt_InvokeFromThread
20. QMutex JasonQt_InvokeFromThread::g_mutex;
21. QMap< QThread *, JasonQt_InvokeFromThreadHelper * > JasonQt_InvokeFromThread::g_helpers;
22. void JasonQt_InvokeFromThread::invoke(QThread *thread, const std::function<void ()> &callback)
23. {
24. if(!(thread->isRunning()))
25. {
26. qDebug() << "JasonQt_InvokeFromThread::invoke: Target thread" << thread << "is not running!";
27. return;
28. }
29. g_mutex.lock();
30. auto it = g_helpers.find(thread);
31. if(it == g_helpers.end())
32. {
33. auto helper = new JasonQt_InvokeFromThreadHelper;
34. helper->moveToThread(thread);
35. QObject::connect(thread, &QThread::finished, [=]()
36. {
37. g_mutex.lock();
38. auto it = g_helpers.find(thread);
39. if(it != g_helpers.end())
40. {
41. g_helpers.erase(it);
42. }
43. g_mutex.unlock();
44. });
45. g_helpers.insert( thread, helper );
46. it = g_helpers.find(thread);
47. }
48. it.value()->addCallback(callback);
49. QMetaObject::invokeMethod(it.value(), "onRun", Qt::QueuedConnection);
50. g_mutex.unlock();
51. }
52. void JasonQt_InvokeFromThread::waitForInvoke(QThread *thread, const std::function<void ()> &callback)
53. {
54. if(!(thread->isRunning()))
55. {
56. qDebug() << "JasonQt_InvokeFromThread::waitForInvoke: Target thread" << thread << "is not running!";
57. return;
58. }
59. g_mutex.lock();
60. auto it = g_helpers.find(thread);
61. if(it == g_helpers.end())
62. {
63. auto helper = new JasonQt_InvokeFromThreadHelper;
64. helper->moveToThread(thread);
65. QObject::connect(thread, &QThread::finished, [=]()
66. {
67. g_mutex.lock();
68. auto it = g_helpers.find(thread);
69. if(it != g_helpers.end())
70. {
71. g_helpers.erase(it);
72. }
73. g_mutex.unlock();
74. });
75. g_helpers.insert( thread, helper );
76. it = g_helpers.find(thread);
77. }
78. it.value()->addCallback([&]()
79. {
80. g_mutex.unlock();
81. callback();
82. });
83. QMetaObject::invokeMethod(it.value(), "onRun", Qt::QueuedConnection);
84. g_mutex.lock();
85. g_mutex.unlock();
86. }

测试代码：

[cpp] view plain copy

1. int main(int argc, char *argv[])
2. {
3. QCoreApplication a(argc, argv);
4. qDebug() << "Main thread:" << QThread::currentThread();
5. constexpr auto threadCount = 5;
6. QVector< QObject * > objects;
7. QThreadPool threadPool;
8. objects.resize(threadCount);
9. threadPool.setMaxThreadCount(threadCount);
10. for(auto i = 0; i < threadCount; i++)
11. {
12. QtConcurrent::run([&objects, i]()
13. {
14. objects[i] = new QObject;
15. qDebug() << "Thread started:" << QThread::currentThread();
16. QEventLoop().exec();
17. });
18. }
19. // 等待测试线程启动
20. QThread::sleep(3);
21. // 调用
22. for(auto i = 0; i < (threadCount * 2); i++)
23. {
24. // 第一个参数是目标线程，第二个是回调
25. JasonQt_InvokeFromThread::invoke(objects[i % threadCount]->thread(), [=]()
26. {
27. qDebug() << "Current thread:" << QThread::currentThread() << ", Flag:" << i;
28. });
29. }
30. return a.exec();
31. }

执行输出

[cpp] view plain copy

1. Main thread: QThread(0x7f821951bf30)
2. Thread started: QThread(0x7f8219705ac0, name = "Thread (pooled)")
3. Thread started: QThread(0x7f8219705f90, name = "Thread (pooled)")
4. Thread started: QThread(0x7f82197055f0, name = "Thread (pooled)")
5. Thread started: QThread(0x7f8219705120, name = "Thread (pooled)")
6. Thread started: QThread(0x7f8219704950, name = "Thread (pooled)")
7. Current thread: QThread(0x7f8219704950, name = "Thread (pooled)") , Flag: 0
8. Current thread: QThread(0x7f8219705ac0, name = "Thread (pooled)") , Flag: 3
9. Current thread: QThread(0x7f8219705120, name = "Thread (pooled)") , Flag: 1
10. Current thread: QThread(0x7f82197055f0, name = "Thread (pooled)") , Flag: 2
11. Current thread: QThread(0x7f8219705f90, name = "Thread (pooled)") , Flag: 4
12. Current thread: QThread(0x7f8219704950, name = "Thread (pooled)") , Flag: 5
13. Current thread: QThread(0x7f8219705ac0, name = "Thread (pooled)") , Flag: 8
14. Current thread: QThread(0x7f8219705120, name = "Thread (pooled)") , Flag: 6
15. Current thread: QThread(0x7f8219705f90, name = "Thread (pooled)") , Flag: 9
16. Current thread: QThread(0x7f82197055f0, name = "Thread (pooled)") , Flag: 7

可以看见，回调被执行在了测试线程中。

注：目标线程需要有运行Qt的事件循环，这是必须的。

http://blog.csdn.net/wsj18808050/article/details/49950871