/
     * 此方法為android程式寫入sd檔案檔案，用到了android-annotation的支援庫@
     *
     * @param buffer   寫入檔案的內容
     * @param folder   儲存檔案的資料夾名稱,如log；可為null，預設儲存在sd卡根目錄
     * @param fileName 檔名稱，預設app_log.txt
     * @param append   是否追加寫入，true為追加寫入，false為重寫檔案
     * @param autoLine 針對追加模式，true為增加時換行，false為增加時不換行
     */
    public synchronized static void writeFileToSDCard(@NonNull final byte[] buffer, @Nullable final String folder,
                                                      @Nullable final String fileName, final boolean append, final boolean autoLine) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                boolean sdCardExist = Environment.getExternalStorageState().equals(
                        android.os.Environment.MEDIA_MOUNTED);
                String folderPath = "";
                if (sdCardExist) {
                    //TextUtils為android自帶的幫助類
                    if (TextUtils.isEmpty(folder)) {
                        //如果folder為空，則直接儲存在sd卡的根目錄
                        folderPath = Environment.getExternalStorageDirectory()
                                + File.separator;
                    } else {
                        folderPath = Environment.getExternalStorageDirectory()
                                + File.separator + folder + File.separator;
                    }
                } else {
                    return;
                }

                File fileDir = new File(folderPath);
                if (!fileDir.exists()) {
                    if (!fileDir.mkdirs()) {
                        return;
                    }
                }
                File file;
                //判斷檔名是否為空
                if (TextUtils.isEmpty(fileName)) {
                    file = new File(folderPath + "app_log.txt");
                } else {
                    file = new File(folderPath + fileName);
                }
                RandomAccessFile raf = null;
                FileOutputStream out = null;
                try {
                    if (append) {
                        //如果為追加則在原來的基礎上繼續寫檔案
                        raf = new RandomAccessFile(file, "rw");
                        raf.seek(file.length());
                        raf.write(buffer);
                        if (autoLine) {
                            raf.write("\n".getBytes());
                        }
                    } else {
                        //重寫檔案，覆蓋掉原來的資料
                        out = new FileOutputStream(file);
                        out.write(buffer);
                        out.flush();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    try {
                        if (raf != null) {
                            raf.close();
                        }
                        if (out != null) {
                            out.close();
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }