我们一起修个草棚过冬吧

使用WWW.LoadFromCacheOrDownload方法加载文件时，其进度（www.progress）在IOS（iPhone/iPad）上只有0和1两个值，不会（0.1,0.2,0.3……）这样平滑的过渡，但在PC和Android上能正常。

解决方法是：1、按照下面设置好HTTP头，2、将要下载的文件后缀设置好mime类型（application/octet-stream ）

参照：http://answers.unity3d.com/questions/594668/wwwprogress-not-working-on-android-ios-1.html

Typically you see this behaviour when the server is returning bad header information. If it's not returning a content length, Unity has no way of giving you progress, since progress is a percentage of the total content length.

Server code :

 $attachment_location = 'files/myAssetBundle.unity3d';
 header($_SERVER["SERVER_PROTOCOL"] . " 200 OK");
 header("Cache-Control: public");
 header("Content-Type: application/zip");
 header("Content-Transfer-Encoding: Binary");
 header("Content-Length:".filesize($attachment_location));
 header("Content-Disposition: attachment; filename=myAssetBundle.unity3d");
 readfile($attachment_location);
 Die();