how to accees Environment.getExternalStorageDirectory() when user connected to system

I am working on email application. My application will create some files in the Sd card.

I am using

   Environment.getExternalStorageDirectory() 

to store the files in SD card. But I have observed that some times when my device connected to my computer I am unable to access my files.

Please suggest what's the path I need to use so that my files must always accessible.

I want to store my files only i开发者_运维技巧n Sd card.

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I think when the SD card is mounted you cannot access it.