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？？