Qt中的QThread：使用QSemaphore进行多线程数据同步
20210127：在生产者、消费者的方法中添加线程挂起方法QThread::usleep(10)，使ui不卡。
避免引起主线程的阻塞，Qt在子线程中处理大数据，当多个子线程需要处理同一块数据时，需要使用数据同步，避免出现调用错乱情况，在这里我们在两个子线程使用QSemaphore作为标志位，对数组进行标识，生产者线程将生成的资源存入数组，消费者数组消耗数组内的资源，当有一方的速度过快导致数组资源耗尽时，该子线程被阻塞，直到有资源时子线程继续。代码如下：
在全局变量中声明数组、数组大小、资源总量：
constant_variable.h
#ifndef CONSTANT_VARIABLE_H
#define CONSTANT_VARIABLE_H
// 所有变量在h文件中均是声明，定义在cpp文件中
/*****************************************************************************************
@copyright 2013-2020
@author qiaowei
@contact weiweiqiao@126.com
@version 1.0
@date 2021-01-24
@brief h文件声明extern变量，cpp文件定义变量
******************************************************************************************/
#include <QSemaphore>
/***************************************************************************
@copyright 2013-2020
@author qiaowei
@contact weiweiqiao@126.com
@version 1.0
@date 2021-01-24
@brief 设置循环保存数据的数组大小，相当于设置“缓存”大小
***************************************************************************/
extern const int BUFFER_SIZE;
/***************************************************************************
@copyright 2013-2020
@author qiaowei
@contact weiweiqiao@126.com
@date 2021-01-24
@brief 要读取的总资源数量，数据量大，无法一次读取完，需要长时间，分批读取
***************************************************************************/
extern const int DATA_SIZE;
/***************************************************************************
@copyright 2013-2020
@author qiaowei
@contact weiweiqiao@126.com
@date 2021-01-24
@brief 循环使用，保存数据资源的数组
***************************************************************************/
extern char BUFFER[];
/***************************************************************************
@copyright 2013-2020
@author qiaowei
@contact weiweiqiao@126.com
@date 2021-01-24
@brief 标识Producer可以保存资源的空余位置的数量，保存在数组中的数据量，因为初
始状态数组中没有任何数据，数组有DATA_SIZE个资源可用
***************************************************************************/
extern QSemaphore PRODUCER_SPACE;
/***************************************************************************
@copyright 2013-2020
@author qiaowei
@contact weiweiqiao@126.com
@date 2021-01-24
@brief 标识Consumer可以使用的已保存资源的数量，因为初始时没有数据可供Consumer
使用，初始资源有0个
***************************************************************************/
extern QSemaphore CONSUMER_SPACE;
#endif // CONSTANT_VARIABLE_H
constant_variable.cpp
#include "constant_variable.h"
const int BUFFER_SIZE(4096);
const int DATA_SIZE(100000);
// 定义数组大小为BUFFER_SIZE
char BUFFER[BUFFER_SIZE];
// 初始时可用资源位BUFFER_SIZE
QSemaphore PRODUCER_SPACE(BUFFER_SIZE);
QSemaphore CONSUMER_SPACE(0);
创建窗体：
Producer按钮生成资源，保存到数组中，在左侧文本框中显示Producer所在的线程及生成的资源。Consumer按钮消耗数组中的资源，在左侧文本框中显示Consumer所在的线程及消耗的资源。这两个按钮是单独运行。Both_start_PushButton按钮同时启动两个子线程，一个生产资源，一个消耗资源，生产和消耗的都在左边的文本框中显示。
窗口代码如下：
producer_consumer_dialog.ui 代码：
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>Producer_consumer_dialog</class>
<widget class="QDialog" name="Producer_consumer_dialog">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>465</width>
<height>451</height>
</rect>
</property>
<property name="windowTitle">
<string>Dialog</string>
</property>
<layout class="QGridLayout" name="gridLayout">
<item row="0" column="0">
<layout class="QVBoxLayout" name="verticalLayout_3">
<item>
<layout class="QHBoxLayout" name="horizontalLayout">
<item>
<widget class="QPlainTextEdit" name="producer_plainTextEdit"/>
</item>
<item>
<layout class="QVBoxLayout" name="verticalLayout">
<item>
<widget class="QPushButton" name="producer_pushButton">
<property name="text">
<string>Producer</string>
</property>
</widget>
</item>
<item>
<spacer name="verticalSpacer">
<property name="orientation">
<enum>Qt::Vertical</enum>
</property>
<property name="sizeType">
<enum>QSizePolicy::Expanding</enum>
</property>
<property name="sizeHint" stdset="0">
<size>
<width>20</width>
<height>40</height>
</size>
</property>
</spacer>
</item>
</layout>
</item>
</layout>
</item>
<item>
<layout class="QHBoxLayout" name="horizontalLayout_2">
<item>
<widget class="QPlainTextEdit" name="consumer_plainTextEdit"/>
</item>
<item>
<layout class="QVBoxLayout" name="verticalLayout_2">
<item>
<widget class="QPushButton" name="consumer_pushButton">
<property name="text">
<string>Consumer</string>
</property>
</widget>
</item>
<item>
<spacer name="verticalSpacer_2">
<property name="orientation">
<enum>Qt::Vertical</enum>
</property>
<property name="sizeHint" stdset="0">
<size>
<width>20</width>
<height>40</height>
</size>
</property>
</spacer>
</item>
</layout>
</item>
</layout>
</item>
<item>
<layout class="QHBoxLayout" name="horizontalLayout_3">
<item>
<spacer name="horizontalSpacer">
<property name="orientation">
<enum>Qt::Horizontal</enum>
</property>
<property name="sizeHint" stdset="0">
<size>
<width>348</width>
<height>20</height>
</size>
</property>
</spacer>
</item>
<item>
<widget class="QPushButton" name="both_start_pushButton">
<property name="text">
<string>Both_start_PushButton</string>
</property>
</widget>
</item>
</layout>
</item>
</layout>
</item>
</layout>
</widget>
<resources/>
<connections/>
</ui>
producer_consumer_dialog.h 文件：
#ifndef PRODUCER_CONSUMER_DIALOG_H
#define PRODUCER_CONSUMER_DIALOG_H
#include <QDialog>
#include <QThread>
QT_BEGIN_NAMESPACE
class Producer_move_to_thread;
class Consumer_move_to_thread;
QT_END_NAMESPACE
namespace Ui {
class Producer_consumer_dialog;
}
/*****************************************************************************************
@copyright 2013-2020
@author qiaowei
@contact weiweiqiao@126.com
@version 1.0
@date 2021-01-27
@brief 创建主窗口，生成创造者producer，并在子线程-1生产资源。生成消费者consumer，并在子线程-2消耗生
产资源。资源均存储在BUFFER[]中
******************************************************************************************/
class Producer_consumer_dialog : public QDialog
{
Q_OBJECT
public:
explicit Producer_consumer_dialog(QWidget *parent = nullptr);
~Producer_consumer_dialog();
private:
/***************************************************************************
@author qiaowei
@contact weiweiqiao@126.com
@version 1.0
@date 2021-01-27
@brief 初始化窗体控件
***************************************************************************/
void init_widgets();
/***************************************************************************
@author qiaowei
@contact weiweiqiao@126.com
@version 1.0
@date 2021-01-27
@brief 初始化私有变量，将producer_，consumer_放入各自的子线程
***************************************************************************/
void init_instances();
/***************************************************************************
@author qiaowei
@contact weiweiqiao@126.com
@version 1.0
@date 2021-01-27
@brief 实例化信号槽
***************************************************************************/
void init_connections();
private slots:
/***************************************************************************
@author qiaowei
@contact weiweiqiao@126.com
@version 1.0
@date 2021-01-27
@brief 将字符串content设置到文本框producer_plainTextEdit
@param content 字符串
***************************************************************************/
void set_producer_plain_text(QString content);
/***************************************************************************
@author qiaowei
@contact weiweiqiao@126.com
@version 1.0
@date 2021-01-27
@brief 将字符串content设置到文本框consumer_plainTextEdit
@param content 字符串
***************************************************************************/
void set_consumer_plain_text(QString content);
private:
Ui::Producer_consumer_dialog *ui;
Producer_move_to_thread* producer_;
Consumer_move_to_thread* consumer_;
QThread producer_thread_;
QThread consumer_thread_;
};
#endif // PRODUCER_CONSUMER_DIALOG_H
producer_consumer_dialog.cpp文件：
#include "producer_consumer_dialog.h"
#include "ui_producer_consumer_dialog.h"
#include "producer_move_to_thread.h"
#include "consumer_move_to_thread.h"
Producer_consumer_dialog::Producer_consumer_dialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::Producer_consumer_dialog)
{
ui->setupUi(this);
init_widgets();
init_instances();
init_connections();
}
Producer_consumer_dialog::~Producer_consumer_dialog()
{
producer_thread_.quit();
producer_thread_.wait();
consumer_thread_.quit();
consumer_thread_.wait();
delete producer_;
delete consumer_;
delete ui;
}
void Producer_consumer_dialog::init_widgets()
{
setFixedSize(sizeHint());
}
void Producer_consumer_dialog::init_instances()
{
producer_ = new Producer_move_to_thread();
producer_->moveToThread(&producer_thread_);
producer_thread_.start();
consumer_ = new Consumer_move_to_thread();
consumer_->moveToThread(&consumer_thread_);
consumer_thread_.start();
}
void Producer_consumer_dialog::init_connections()
{
connect(ui->producer_pushButton,
&QPushButton::clicked,
producer_,
&Producer_move_to_thread::create_char_in_thread);
connect(ui->consumer_pushButton,
&QPushButton::clicked,
consumer_,
&Consumer_move_to_thread::create_char_in_thread);
connect(ui->both_start_pushButton,
&QPushButton::clicked,
ui->producer_pushButton,
&QPushButton::clicked);
connect(ui->both_start_pushButton,
&QPushButton::clicked,
ui->consumer_pushButton,
&QPushButton::clicked);
// 获取producer_生成的字符串
connect(producer_,
&Producer_move_to_thread::signal_string,
this,
&Producer_consumer_dialog::set_producer_plain_text);
// 获取consumer_取得的字符串
connect(consumer_,
&Consumer_move_to_thread::signal_string,
this,
&Producer_consumer_dialog::set_consumer_plain_text);
}
void Producer_consumer_dialog::set_producer_plain_text(QString content)
{
ui->producer_plainTextEdit->appendPlainText(content);
// ui->producer_plainTextEdit->setPlainText(content);
}
void Producer_consumer_dialog::set_consumer_plain_text(QString content)
{
ui->consumer_plainTextEdit->appendPlainText(content);
// ui->consumer_plainTextEdit->setPlaceholderText(content);
}
生产类
producer_move_to_thread.h 文件：
#ifndef PRODUCER_MOVE_TO_THREAD_H
#define PRODUCER_MOVE_TO_THREAD_H
#include <QObject>
class Producer_move_to_thread : public QObject
{
Q_OBJECT
public:
explicit Producer_move_to_thread(QObject *parent = nullptr);
signals:
void signal_string(QString content);
public slots:
void create_char_in_thread();
};
#endif // PRODUCER_MOVE_TO_THREAD_H
producer_move_to_thread.cpp 文件：
#include <QtDebug>
#include <QThread>
#include "producer_move_to_thread.h"
#include "constant_variable.h"
Producer_move_to_thread::Producer_move_to_thread(QObject* parent):
QObject(parent)
{
}
void Producer_move_to_thread::create_char_in_thread()
{
for (int index(0); DATA_SIZE != index; ++index) {
// 生产1个资源（总共要产生的DATA_SZIE个资源），然后保存到BUFFER数组，BUFFER数组空余位置少1个
PRODUCER_SPACE.acquire(1);
// 根据取余数结果在数组循环保存生产的资源
BUFFER[index % BUFFER_SIZE] = "ABCDXYZ"[uint(std::rand()) % 7];
qDebug()<< "Produce thread id: " << (quint64) QThread::currentThreadId()
<< ", char: " << BUFFER[index % BUFFER_SIZE];
QString content =
QString("%1: Producer thread id: %2, char: %3").
arg(index + 1).
arg((quint64) QThread::currentThreadId()).
arg(BUFFER[index % BUFFER_SIZE]);
emit signal_string(content);
//线程挂起，不对主线程造成卡顿
QThread::usleep(10);
// 数组中已保存1个字符，Consumer获取1个可用资源
CONSUMER_SPACE.release(1);
}
}
资源消耗类
consumer_move_to_thread.h 文件：
#ifndef CONSUMER_MOVE_TO_THREAD_H
#define CONSUMER_MOVE_TO_THREAD_H
#include <QObject>
class Consumer_move_to_thread : public QObject
{
Q_OBJECT
public:
explicit Consumer_move_to_thread(QObject *parent = nullptr);
signals:
void signal_string(QString content);
public slots:
void create_char_in_thread();
};
#endif // CONSUMER_MOVE_TO_THREAD_H
consumer_move_to_thread.cpp文件：
#include <QtDebug>
#include <QThread>
#include "consumer_move_to_thread.h"
#include "constant_variable.h"
Consumer_move_to_thread::Consumer_move_to_thread(QObject *parent) :
QObject(parent)
{
}
void Consumer_move_to_thread::create_char_in_thread()
{
for (int index(0); DATA_SIZE != index; ++index) {
// 消耗1个资源（总共要消耗DATA_SZIE个资源），从BUFFER数组中取出，BUFFER数组空余位置多1个。当
// 没有资源提供时，进程被挂起，待有足够资源后再执行后续程序
CONSUMER_SPACE.acquire(1);
qDebug()<< "Consumer thread id: " << (quint64) QThread::currentThreadId()
<< ", char: " << (char) BUFFER[index % BUFFER_SIZE];
QString content =
QString("%1: Consumer thread id: %2, char: %3").
arg(index + 1).
arg((quint64) QThread::currentThreadId()).
arg(BUFFER[index % BUFFER_SIZE]);
emit signal_string(content);
//线程挂起，不对主线程造成卡顿
QThread::usleep(10);
// 使用数组中1个资源，数组释放1个空间，给生产者提供1个空余位置
PRODUCER_SPACE.release(1);
}
}
在这里特别注意PRODUCER_SPACE和CONSUMER_SPACE的初始值，因为资源BUFFER数组初始资源为0，所以生产者Producer可用的数组空间为所有，消耗着Consumer可用的数组空间为0，因为没有资源可用。
运行结果如下图：
注：因为数据在窗体控件上显示只能在主线程运行，当大量数据在窗体控件上设置时，会是的窗体有卡顿情况，该怎么改进避免窗体卡顿，有谁知道该怎么改进么？？
