没有在Android的开放Office文件的标准API。该应用程序你发现使用的内部API，用于读取文件。它们要么为此在设备或他们的文件上传到服务器，这是负责分析文件，并将其转换成一种格式，它是从Android客户端更容易阅读。

There isn't a standard API for opening office files in Android. The applications you've found use an internal API for reading the files. They either do this in the device or they upload the file to a server, which is responsible for parsing the file and convert it to a format that is easier read from the Android client.