安卓上为什么不能用system.io.file读取streammingAssets目录下的文件

首先，看文档：

Streaming Assets

 

Most assets in Unity are combined into the project when it is built. However, it is sometimes useful to place files into the normal filesystem on the target machine to make them accessible via a pathname. An example of this is the deployment of a movie file on iOS devices; the original movie file must be available from a location in the filesystem to be played by the PlayMovie function.

Any files placed in a folder called StreamingAssets (case-sensitive) in a Unity project will be copied verbatim to a particular folder on the target machine. You can retrieve the folder using the Application.streamingAssetsPathproperty. It’s always best to use Application.streamingAssetsPath to get the location of the StreamingAssets folder, as it will always point to the correct location on the platform where the application is running.

The location of this folder varies per platform. Please note that these are case-sensitive:

• On a desktop computer (Mac OS or Windows) the location of the files can be obtained with the following code:

   path = Application.dataPath + "/StreamingAssets";
  

• On iOS, use:

   path = Application.dataPath + "/Raw";
  

• On Android, use:

   path = "jar:file://" + Application.dataPath + "!/assets/";
  

On Android, the files are contained within a compressed .jar file (which is essentially the same format as standard zip-compressed files). This means that if you do not use Unity’s WWW class to retrieve the file, you need to use additional software to see inside the .jar archive and obtain the file.

Note: .dll files located in the StreamingAssets folder don’t participate in the compilation.

总结：在安卓上，streamingAssets目录是在一个jar压缩包中，路径为：path = "jar:file://" + Application.dataPath + "!/assets/"; 因为jar是压缩包，因此不能使用普通的文件读取方式，WWW带解压功能，可以使用它