一、效果图

界面中有一个Label，一个Button
点击Buttion，显示Loading的界面，并覆盖到Label和Button上面

二、Loading

loadingwidget.h

#ifndef LOADINGWIDGET_H
#define LOADINGWIDGET_H#include <QTimer>
#include <QWidget>class LoadingWidget : public QWidget
{
Q_OBJECT
public:
explicit LoadingWidget(QWidget *parent = nullptr);signals:// QWidget interface
protected:
void paintEvent(QPaintEvent *event) override;
void timerEvent(QTimerEvent *event) override;
void showEvent(QShowEvent *event) override;
void hideEvent(QHideEvent *event) override;private slots:
void startUpdateTimer();
void stopUpdateTimer();private:
QTimer *timer;
int m_timerID = -1;
const int UPDATE_INTERVAL_TIME = 60; //msint m_angle = 0;  // 旋转的角度};#endif // LOADINGWIDGET_H

loadingwidget.cpp

#include "loadingwidget.h"#include <QPainter>
#include <QDebug>LoadingWidget::LoadingWidget(QWidget *parent): QWidget{parent}
{setAttribute(Qt::WA_StyledBackground);setStyleSheet("QWidget{background-color: rgba(0, 0, 0, 127);}");
}void LoadingWidget::paintEvent(QPaintEvent *event)
{QPainter painter(this);painter.setRenderHint(QPainter::Antialiasing);// 定义旋转中心和旋转角度painter.translate(width() / 2, height() / 2);painter.rotate(m_angle);// 设置笔的宽度和颜色，并画圆int radius = width() / 20;    // 圆的半径QPen pen;pen.setWidth(radius / 5);pen.setColor(QColor(0, 0, 0, 127));painter.setPen(pen);painter.drawEllipse(-radius, -radius, 2*radius, 2*radius);// 在圆上画一个定义好颜色的扇形外边框pen.setColor(QColor(0, 160, 230));painter.setPen(pen);painter.drawArc(-radius, -radius, 2*radius, 2*radius, 0 * 16, 90 * 16);}void LoadingWidget::timerEvent(QTimerEvent *event)
{m_angle = (m_angle + 10) % 360; // 每次旋转10度update();qDebug() << "update " << m_angle;
}void LoadingWidget::showEvent(QShowEvent *event)
{QMetaObject::invokeMethod(this, "startUpdateTimer");
}void LoadingWidget::hideEvent(QHideEvent *event)
{QMetaObject::invokeMethod(this, "stopUpdateTimer");
}void LoadingWidget::startUpdateTimer()
{if(m_timerID == -1){// 每 UPDATE_INTERVAL_TIME 毫秒触发定时器，执行timerEvent，更新UIm_timerID = startTimer(UPDATE_INTERVAL_TIME);}
}void LoadingWidget::stopUpdateTimer()
{if (m_timerID != -1) {killTimer(m_timerID);m_timerID = -1;}
}

三、使用

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H#include "loadingwidget.h"#include <QMainWindow>QT_BEGIN_NAMESPACE
namespace Ui {
class MainWindow;
}
QT_END_NAMESPACEclass MainWindow : public QMainWindow
{Q_OBJECTpublic:MainWindow(QWidget *parent = nullptr);~MainWindow();private slots:void on_pushButton_clicked();private:Ui::MainWindow *ui;LoadingWidget* loadingWidget;// QWidget interface
protected:void resizeEvent(QResizeEvent *event) override;};
#endif // MAINWINDOW_H

mainwindow.cpp

#include "loadingwidget.h"
#include "mainwindow.h"
#include "ui_mainwindow.h"MainWindow::MainWindow(QWidget *parent): QMainWindow(parent), ui(new Ui::MainWindow)
{ui->setupUi(this);loadingWidget = new LoadingWidget(this);loadingWidget->setFixedSize(width(), height());  // 设置窗口大小loadingWidget->hide();
}MainWindow::~MainWindow()
{delete ui;
}void MainWindow::on_pushButton_clicked()
{loadingWidget->show();// 点击按钮显示Loading界面后，10秒结束显示QTimer::singleShot(10000, [this](){loadingWidget->hide();});
}// Loading界面的大小随父窗口的大小而改变
void MainWindow::resizeEvent(QResizeEvent *event)
{loadingWidget->setFixedSize(width(), height());  // 设置窗口大小
}