Getting all the total and available space on Android

Here is how you get internal storage sizes:

 StatFs statFs = new StatFs(Environment.getRootDirectory().getAbsolutePath());        
 long blockSize = statFs.getBlockSize();
 long totalSize = statFs.getBlockCount()*blockSize;
 long availableSize = statFs.getAvailableBlocks()*blockSize;
 long freeSize = statFs.getFreeBlocks()*blockSize;

Here is how you get external storage sizes (SD card size):

 StatFs statFs = new StatFs(Environment.getExternalStorageDirectory().getAbsolutePath());        
 long blockSize = statFs.getBlockSize();
 long totalSize = statFs.getBlockCount()*blockSize;
 long availableSize = statFs.getAvailableBlocks()*blockSize;
 long freeSize = statFs.getFreeBlocks()*blockSize;

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Short note

Free blocks:

The total number of blocks that are
free on the file system, including
reserved blocks (that are not
available to normal applications).

Available blocks:

The number of blocks that are free on
the file system and available to
applications.

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Here is how to detect whether SD card is mounted:

 String state = Environment.getExternalStorageState();
 if (Environment.MEDIA_MOUNTED.equals(state)) 
 {
   // We can read and write the media    
 } 
 else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) 
 {
    // We can only read the media     
 } 
 else 
 {
    // No external media
 }