Qt 倒计时或定时器的简单实现

1.相关说明

QTimer类实现定时器或倒计时

2.界面绘制

3.相关主要代码

// widget.h
typedef struct TimeHMS{
    qint32 hour;
    qint32 minute;
    qint32 second;
}TimeHMS;

// widget.cpp
#include "widget.h"
#include "ui_widget.h"
#include <QTime>
#include <QTimer>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    this->hms.hour = 0;
    this->hms.minute = 0;
    this->hms.second = 0;
    m_timer = new QTimer(this);
    m_timer->stop();    // 默认定时器关闭
    m_timer->setSingleShot(false);
    m_timer->setTimerType(Qt::PreciseTimer);
    // 间隔时间 1s
    m_timer->setInterval(1000);
    connect(m_timer, &QTimer::timeout, this, &Widget::do_timer_timeout);
}

Widget::~Widget()
{
    delete ui;
}


// 减一秒
bool Widget::subtractOneSecond()
{
    // 若全部等于0，则返回false
    if(hms.second <= 0 && hms.minute == 0 && hms.hour == 0){
        return false;
    }
    // 秒钟减1
    hms.second--;
    if(hms.second < 0){
        hms.minute--;
        hms.second = 59;
        if(hms.minute < 0){
            hms.hour--;
            hms.minute = 59;
        }
    }
    return true;
}

void Widget::do_timer_timeout()
{
    bool retBool = this->subtractOneSecond();
    if(!retBool){
        // 停止timer
        m_timer->stop();
        return;
    }
    ui->lcdHour->display(hms.hour);
    ui->lcdMinute->display(hms.minute);
    ui->lcdSecond->display(hms.second);

}

// 开始
void Widget::on_btnStart_clicked()
{
    m_timer->start();
    QTime tm = ui->timeEdit->time();
    this->hms.hour = tm.hour();
    this->hms.minute = tm.minute();
    this->hms.second = tm.second();
    qDebug("Hour=%d", tm.hour());
    qDebug("Minute=%d", tm.minute());
    qDebug("Second=%d", tm.second());
}
// 停止
void Widget::on_btnStop_clicked()
{
    m_timer->stop();
}