QNetworkAccessManager uploadProgress和QProgressBar

Question

我有一个QT程序,使用QNetworkAccessManager通过Http POST上传一组文件.一切都上传得很好,但是我无法将uploadProgress与进度条连接起来.

这是上传的代码:

QNetworkAccessManager *networkManager = new QNetworkAccessManager(this);
while (numNetConn > 3) {
    qDebug("Waiting for the number of transfers to decrease. [%d]", numNetConn);
    QTest::qWait(500);
}
QNetworkReply* reply = networkManager->post(request, multiPart);
multiPart->setParent(reply); // delete the multiPart with the reply
connect(reply, SIGNAL(finished()), this, SLOT(onGetReply()));
connect(reply, SIGNAL(uploadProgress(qint64, qint64)), SLOT(progressChanged(qint64, qint64)));

void MainWindow::progressChanged(qint64 a, qint64 b) {
    if (b > 0) {
        qDebug() << "Uploading " << a  << "/" << b << "%" << (double)a/(double)b*100.0;
        ui->progUpload->setValue((a/b)*100);
        qApp->processEvents();
    }
}

调试窗口在上传时愉快地显示了很多进度,但是在上传到100%时,UI才会在上传结束时更新.

...
Uploading  171606016 / 172918683 % 99.2409
Uploading  171835392 / 172918683 % 99.3735
Uploading  172064768 / 172918683 % 99.5062
Uploading  172294144 / 172918683 % 99.6388
Uploading  172523520 / 172918683 % 99.7715
Uploading  172769280 / 172918683 % 99.9136
Uploading  172918683 / 172918683 % 100

我在progressChanged()函数中缺少什么来更新UI？

Answer 1

您的百​​分比计算是:

(a/b)*100

a并且b这里都是整数类型,所以直到a等于b,a/b求值为0.

要获得所需的行为,可以先进行乘法运算:

100*a/b

您也可以将整数转换为float或double(如您在qDebug语句中所做的那样).