https://qiita.com/tyfkda/items/7c07594ee6a7bc56dbc3

[Nyoshi]

“private static String LOCAL_FILE = "ファイル名"; private void writeLogToLocalFile(String message) { try { OutputStream out = openFileOutput(LOCAL_FILE, MODE_PRIVATE | MODE_APPEND); PrintWriter writer = new PrintWriter(new OutputStreamWriter(out,"UTF-8")); writer.append(message + "\n"); write