QT 从指定时间启动倒计时器、暂停和继续功能

场景需求：左边设置一个开始时间，点击开始按钮，右边开始倒计时，暂停按钮控制倒计时的暂停和继续。

实现：

pgsystem.h头文件中加入：

private:
    QDateTimeEdit *pgtimeline;
    QTimer *pgtimer1000;
    QLCDNumber *lcdNumber;
    static int min;//声明静态全局变量
    static int sec;
    static bool clicked;
private slots:
    void pgxtupdateTime1000();
    void starttime();
    void stoptime();

pgsystem.cpp源文件中加入： 

    pgtimeline=new QDateTimeEdit(this);
    pgtimeline->setDisplayFormat("mm分ss秒");

    lcdNumber=new QLCDNumber(this);
    lcdNumber->setDigitCount(8);
    lcdNumber->setSegmentStyle(QLCDNumber::Flat);
    lcdNumber->display("0");

    pgtimer1000=new QTimer;

    connect(beginBtn,&QPushButton::clicked,this,&pgsystem::starttime);//开始按钮槽函数
    connect(stopBtn,&QPushButton::clicked,this,&pgsystem::stoptime);//暂停按钮槽函数
    connect(pgtimer1000,&QTimer::timeout,this,&pgsystem::pgxtupdateTime1000);//倒计时更新


//开始按钮槽函数
int pgsystem::min=0;
int pgsystem::sec=0;
void pgsystem::starttime()
{
    QString strMinute = pgtimeline->sectionText(QDateTimeEdit::MinuteSection);
    QString strSecond = pgtimeline->sectionText(QDateTimeEdit::SecondSection);
    min=strMinute.toInt();
    sec=strSecond.toInt();
    pgtimer1000->start(1000);

}
//暂停按钮槽函数
bool pgsystem::clicked = false;
void pgsystem::stoptime()
{
    QString button_style="QPushButton{background-color:#4682B4;color:white}";
    QString button_style2="QPushButton:pressed{background-color:white;color:#4682B4;border-style:inset;}";
    if(clicked == false)//表示倒计时器处于运行状态，单击之后按钮状态变成“继续”
    {
        stopBtn->setText(QString::fromUtf8("继续"));
        stopBtn->setStyleSheet(button_style2);
        pgtimer1000->stop();
        clicked = true;

    }
    else if(clicked == true)//表示倒计时器处于运行状态，单击之后按钮状态变成“暂停”
    {
    {
        stopBtn->setText(QString::fromUtf8("暂停"));
        stopBtn->setStyleSheet(button_style);
        pgtimer1000->start(1000);
        clicked = false;
    }
}
//倒计时器槽函数
void pgsystem::pgxtupdateTime1000()
{

    if (sec!=0)
    {
        sec=sec-1;
    }
    else if (min!=0)
    {
        sec=59;
        min=min-1;
    }
    else
        pgtimer1000->stop();//分和秒都为0时，停止计时器
lcdNumber->display(QString("%1:%2").arg(QString::number(min)).arg(QString::number(sec)));

}