ソースコード
File path = Environment.getDataDirectory();
StatFs stat = new StatFs(path.getPath());
long availMemSize = stat.getAvailableBlocks() * stat.getBlockSize();
String unit = "";
if (availMemSize > 1024) {
availMemSize /= 1024;
unit = "KB";
if (availMemSize > 1024) {
availMemSize /= 1024;
unit = "MB";
}
}