android get sdcard free size (from miui.fileexplorer)

util.java

//https://github.com/MiCode/FileExplorer/blob/master/src/net/micode/fileexplorer/Util.java
    public static SDCardInfo getSDCardInfo() {
        String sDcString = android.os.Environment.getExternalStorageState();

        if (sDcString.equals(android.os.Environment.MEDIA_MOUNTED)) {
            File pathFile = android.os.Environment.getExternalStorageDirectory();

            try {
                android.os.StatFs statfs = new android.os.StatFs(pathFile.getPath());

                // 获取SDCard上BLOCK总数
                long nTotalBlocks = statfs.getBlockCount();

                // 获取SDCard上每个block的SIZE
                long nBlocSize = statfs.getBlockSize();

                // 获取可供程序使用的Block的数量
                long nAvailaBlock = statfs.getAvailableBlocks();

                // 获取剩下的所有Block的数量(包括预留的一般程序无法使用的块)
                long nFreeBlock = statfs.getFreeBlocks();

                SDCardInfo info = new SDCardInfo();
                // 计算SDCard 总容量大小MB
                info.total = nTotalBlocks * nBlocSize;

                // 计算 SDCard 剩余大小MB
                info.free = nAvailaBlock * nBlocSize;

                return info;
            } catch (IllegalArgumentException e) {
                Log.e(LOG_TAG, e.toString());
            }
        }

        return null;
    }