Question

我正在尝试显示从使用networkaccess manager获取的get请求中获取的图像。我能够编译甚至能够运行它。但是我无法在Qlabel中显示图像。

QNetworkAccessManager* nam;

void MainWindow::on_pushButton_clicked()
{
    nam = new QNetworkAccessManager(this);
    QUrl url("http://i.imgur.com/Uw7Fk.jpg");
    QNetworkReply* reply = nam->get(QNetworkRequest(url));
    if (reply->error() == QNetworkReply::NoError)
    {
        QImageReader imageReader(reply);
        imageReader.setAutoDetectImageFormat (false);
        QImage pic = imageReader.read();
        ui->label_2->setPixmap(QPixmap::fromImage(pic));

     }


}

请告诉我哪里出错了。

Answer 1

调用QNetworkReply后，QNetworkAccessManager::get()中的数据尚未就绪。该调用是异步的，您需要在尝试检索任何数据之前连接到QNetworkAccessManager的finished()信号或QNetworkReply的readyRead()信号。

Answer 2

要同步获取图像，您可以使用如下的QEventLoop：

QNetworkAccessManager* nam;

void MainWindow::on_pushButton_clicked()
{
    nam = new QNetworkAccessManager(this);
    QUrl url("http://i.imgur.com/Uw7Fk.jpg");
    QNetworkReply* reply = nam->get(QNetworkRequest(url));

    QEventLoop eventloop;
    connect(reply,SIGNAL(finished()),&eventloop,SLOT(quit()));
    eventLoop.exec();

    if (reply->error() == QNetworkReply::NoError)
    {
        QImageReader imageReader(reply);
        imageReader.setAutoDetectImageFormat (false);
        QImage pic = imageReader.read();
        ui->label_2->setPixmap(QPixmap::fromImage(pic));

     }


}

QT显示从网络访问管理器获得的图像

2 个答案: