// 1线程同步
QFutureSynchronizer synchronizer;

//2线程1

synchronizer.addFuture(QtConcurrent::run([=]() {
download(url);
}));

//3线程2

synchronizer.addFuture(QtConcurrent::run([=]() {
download(webpicurl);
}));

//4等待下载完成

synchronizer.waitForFinished();

//5ToSomeThing