#include "mainwindow.h" #include "ui_mainwindow.h" #include<QMessageBox> #include<QTextEdit> #include<QPushButton> TemperatureThread::TemperatureThread(QObject *parent) : QThread(parent) { m_temperature = 0.0; QPushButton * btn= new QPushButton(); //btn->show(); btn->setText("this"); btn->setParent(QObject); } void TemperatureThread::run() { while (true){ m_temperature = qrand() % 100; emit temperatureChanged(m_temperature); msleep(1000); } } MainWindow::MainWindow(QWidget *parent): QMainWindow(parent), ui(new Ui::MainWindow) { ui->setupUi(this); m_temperatureThread = new TemperatureThread(this); m_timer = new QTimer(this); m_threshold = 0.0; connect(m_temperatureThread, &TemperatureThread::temperatureChanged, this,&MainWindow::updateTemperature); } MainWindow::~MainWindow() { delete ui; } void MainWindow::on_startButton_clicked() { if (m_timer->isActive()) { QMessageBox::warning(this,tr("Warning"),tr("Alarm already started")); return; } bool ok; m_threshold = ui->thresholdEdit->text().toDouble(&ok); if (!ok) { QMessageBox::warning(this,tr("warning"),tr("Invalid")); return; } m_temperatureThread->start(); m_timer->start(1000); } void MainWindow::on_stopButton_clicked() { if (!m_timer->isActive()){ QMessageBox::warning(this,tr("Warning"),tr("Alarm not started yet")); return; } m_temperatureThread->quit(); m_temperatureThread->wait(); m_timer->stop(); ui->temperatureLabel->setText(tr("0.0")); } void MainWindow::updateTemperature(double temperature) { ui->temperatureLabel->setText(QString::number(temperature)); if (temperature > m_threshold){ QMessageBox::critical(this,tr("Warning"),tr("Temperature too high")); } }错在哪

代码存在一些问题：

1. 在 TemperatureThread 的构造函数中创建了一个 QPushButton 实例，但并没有将其添加到界面中。

2. 在创建 QPushButton 实例时，使用了 QObject 作为其父对象，应该使用 MainWindow 或其子类作为父对象。

3. 在 on_startButton_clicked 函数中，应该先判断是否已经启动了温度线程，再进行阈值的设置和启动定时器。

4. 在 on_stopButton_clicked 函数中，应该先判断是否已经启动了定时器和温度线程，再停止定时器和温度线程，并将温度显示标签的文本清零。

5. 在 updateTemperature 函数中，应该将温度值转换为字符串后再设置到温度显示标签上。

下面是修改后的代码：

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMessageBox>
#include <QTextEdit>
#include <QPushButton>

TemperatureThread::TemperatureThread(QObject *parent)
    : QThread(parent)
{
    m_temperature = 0.0;
}

void TemperatureThread::run()
{
    while (true){
        m_temperature = qrand() % 100;
        emit temperatureChanged(m_temperature);
        msleep(1000);
    }
}

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

    m_temperatureThread = new TemperatureThread(this);
    m_timer = new QTimer(this);
    m_threshold = 0.0;

    connect(m_temperatureThread, &TemperatureThread::temperatureChanged,
            this, &MainWindow::updateTemperature);
}

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

void MainWindow::on_startButton_clicked()
{
    if (m_temperatureThread->isRunning()) {
        QMessageBox::warning(this,tr("Warning"),tr("Alarm already started"));
        return;
    }

    bool ok;
    m_threshold = ui->thresholdEdit->text().toDouble(&ok);

    if (!ok) {
        QMessageBox::warning(this,tr("warning"),tr("Invalid"));
        return;
    }

    m_temperatureThread->start();
    m_timer->start(1000);
}

void MainWindow::on_stopButton_clicked()
{
    if (!m_timer->isActive() || !m_temperatureThread->isRunning()) {
        QMessageBox::warning(this,tr("Warning"),tr("Alarm not started yet"));
        return;
    }

    m_temperatureThread->quit();
    m_temperatureThread->wait();
    m_timer->stop();

    ui->temperatureLabel->setText(QString::number(0.0));
}

void MainWindow::updateTemperature(double temperature)
{
    ui->temperatureLabel->setText(QString::number(temperature));

    if (temperature > m_threshold){
        QMessageBox::critical(this,tr("Warning"),tr("Temperature too high"));
    }
}