關鍵是：QNetworkAccessManager類用來協調網絡操作，可以調度創建好的請求，并發射信號來報告進度。

運行截圖如下：

代碼如下：

widget.h

#ifndef WIDGET_H #define WIDGET_H#include <QWidget>class QNetworkReply; class QNetworkAccessManager; #include <QUrl> class QFile;namespace Ui { class Widget; }class Widget : public QWidget {Q_OBJECTpublic:explicit Widget(QWidget *parent = 0);~Widget();void startRequest(QUrl url);private slots:void httpFinished();void httpReadyRead();void updateProgress(qint64,qint64);void on_pushButton_clicked();private:Ui::Widget *ui;QNetworkAccessManager *manager;QNetworkReply *reply;QUrl url;QFile *file;};#endif // WIDGET_H

widget.cpp

#include "widget.h" #include "ui_widget.h" #include <QtNetwork>Widget::Widget(QWidget *parent) :QWidget(parent),ui(new Ui::Widget) {ui->setupUi(this);this->setWindowTitle("CSDN IT1995");manager=new QNetworkAccessManager(this);ui->progressBar->hide();connect(ui->pushButton,SIGNAL(clicked(bool)),this,SLOT(on_pushButton_clicked())); }Widget::~Widget() {delete ui; }void Widget::startRequest(QUrl url) {reply=manager->get(QNetworkRequest(url));connect(reply,&QNetworkReply::readyRead,this,&Widget::httpReadyRead);connect(reply,&QNetworkReply::downloadProgress,this,&Widget::updateProgress);connect(reply,&QNetworkReply::finished,this,&Widget::httpFinished); }void Widget::httpFinished() {ui->progressBar->hide();if(file){file->close();delete file;file=0;}reply->deleteLater();reply=0; }void Widget::httpReadyRead() {if(file)file->write(reply->readAll()); }void Widget::updateProgress(qint64 byteRead, qint64 totalBytes) {ui->progressBar->setMaximum(totalBytes);ui->progressBar->setValue(byteRead); }void Widget::on_pushButton_clicked() {url=ui->lineEdit->text();QFileInfo info(url.path());QString fileName(info.fileName());if(fileName.isEmpty())fileName="index.html";file=new QFile(fileName);if(!file->open(QIODevice::WriteOnly)){delete file;file=NULL;return;}startRequest(url);ui->progressBar->setValue(0);ui->progressBar->show(); }

main.cpp

#include "widget.h" #include <QApplication>int main(int argc, char *argv[]) {QApplication a(argc, argv);Widget w;w.show();return a.exec(); }

總結

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