Android SD

首先，要获取SD卡上面的信息，需要添加访问扩展设备的权限。
<uses-permission
android:name="android.permission.WRITE_EXTERNAL_STORAGE">
</uses-permission>
其次，需要判断手机上面SD卡是否插好Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)
取得sdcard文件路径
File path = Environment.getExternalStorageDirectory();
StatFs statfs = new StatFs(path.getPath());
获取block的SIZE
long blocSize = statfs.getBlockSize();
获取BLOCK数量
long totalBlocks = statfs.getBlockCount();
空闲的Block的数量
long availaBlock = statfs.getAvailableBlocks();
计算总空间大小和空闲的空间大小
String[] total = csize(totalBlocks * blocSize);
String[] availale = csize(availaBlock * blocSize);
计算空间方法csize
String[] filesize(long size) {
        String str = "";
        if (size >= 1024) {
            str = "KB";
            size /= 1024;
            if (size >= 1024) {
                str = "MB";
                size /= 1024;
            }
        }
        DecimalFormat formatter = new DecimalFormat();
        formatter.setGroupingSize(3);
        String result[] = new String[2];
        result[0] = formatter.format(size);
        result[1] = str;
        return result;
    }