闹钟项目：

widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QTimerEvent>
#include <QTime>
#include <QDebug>
#include <QTextToSpeech>
#include <QMessageBox>
#include <QTimer>


QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();

    void timerEvent(QTimerEvent *e);   //要重写的关于定时器时间处理函数的声明

private slots:
    void on_startBtn_clicked();

    void on_stopBtn_clicked();

private:
    Ui::Widget *ui;

    QTextToSpeech *speecher;
    QTimer *timer;
    int tId;
};
#endif // WIDGET_H

 widget.cpp

#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);

    ui->hangEdit->setText("20-20-20");
    tId = startTimer(1000);
    this->timer = new QTimer;
    speecher = new QTextToSpeech(this);

}

Widget::~Widget()
{
    delete ui;

}

void Widget::timerEvent(QTimerEvent *e)
{
    if(e->timerId()==tId)
    {

    //获取系统时间
    QTime sys_time = QTime::currentTime();    //QTime类对象

    //将时间转化为字符串
    QString t = sys_time.toString("hh-mm-ss");


    //将字符串展示到ui界面
    ui->syslabel->setText(t);
    ui->syslabel->setAlignment(Qt::AlignCenter);

    if(ui->syslabel->text()==ui->hangEdit->text())
    {
        speecher->say(ui->tEdit->toPlainText());
    }

    }
}

void Widget::on_startBtn_clicked()
{
    if(ui->hangEdit->text()== NULL)
    {
        QMessageBox::critical(this,
                          "错误",
                          "请先编辑时间",
                          QMessageBox::Ok
                                 );
    }
    return;

    timer->start(100);
    ui->hangEdit->setReadOnly(true);
    ui->tEdit->setReadOnly(true);

}

void Widget::on_stopBtn_clicked()
{
    int ret  =   QMessageBox::question(this,
                          "提示",
                          "确定要停止闹钟吗？",
                          QMessageBox::Yes | QMessageBox::No);

    if(ret = QMessageBox::Yes)
    {
        timer->stop();
        ui->hangEdit->setReadOnly(false);
        ui->tEdit->setReadOnly(false);

        ui->hangEdit->clear();
    }

}

 

思维导图：