廢話不多說，直接上程式碼，私有檔案在data/data/appName/下，不能將檔案拷貝

/**
 * 將資料寫入到私有檔案中
 * @param context
 * @param data
 * @param fileName
 */
private void saveDataToFile(Context context, String data, String fileName)
{
    FileOutputStream fileOutputStream = null;
    BufferedWriter bufferedWriter = null;
    try
    {

        fileOutputStream = context.openFileOutput(fileName,
 
                Context.MODE_APPEND);
        bufferedWriter = new BufferedWriter(
                new OutputStreamWriter(fileOutputStream));
        bufferedWriter.write(data);
        Toast.makeText(context, "儲存的資料為"+data, Toast.LENGTH_SHORT).show();

    }
    catch (IOException e)
    {
        e.printStackTrace();
 
    }

    finally
    {
        try
        {
            if (bufferedWriter != null)
            {
                bufferedWriter.close();
            }
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
    }
}

/**
 * 從檔案中讀取資料
 * @param context context
 
 * @param fileName 檔名
 * @return 從檔案中讀取的資料
 */
private String loadDataFromFile(Context context, String fileName)
{
    FileInputStream fileInputStream = null;
    BufferedReader bufferedReader = null;
    StringBuilder stringBuilder = new StringBuilder();
    try
    {
        /**
         * 注意這裡的fileName不要用絕對路徑，只需要檔名就可以了，系統會自動到data目錄下去載入這個檔案
         */
        fileInputStream = context.openFileInput(fileName);
        bufferedReader = new BufferedReader(
                new InputStreamReader(fileInputStream));
        String result = "";
        while ((result = bufferedReader.readLine()) != null)
        {
            stringBuilder.append(result);
        }
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }
    finally
    {
        if (bufferedReader != null)
        {
            try
            {
                bufferedReader.close();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
        }
    }
    return stringBuilder.toString();
}

以文字形式儲存到指定資料夾可以進行拷貝

/**
 * 將資料以文字的形式儲存到指定目錄下
 * @param bytes
 */
private void saveToPublic(byte[] bytes){
    String status = Environment.getExternalStorageState();
    if (status.equals(Environment.MEDIA_MOUNTED)){
        try{
            String filename = newDate();
            File file = new File(Environment.getExternalStorageDirectory()+"/"+"ZRY",filename);
           if (!file.exists()){
               File dir = new File(file.getParent());
               dir.mkdirs();
           }

            FileOutputStream outStream = new FileOutputStream(file+".txt",true);    //檔案輸出流用於將資料寫入檔案
            outStream.write(bytes);
            outStream.close();  //關閉檔案輸出流
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

/**
 * 返回一個時間的名稱
 * @return
 */
public static String newDate(){
    Time time = new Time();
    time.setToNow();
    int year = time.year;
    int month = time.month+1;
    int monthDay = time.monthDay;
    int hour = time.hour;
    int minute = time.minute;
    int second = time.second;
    return ""+year+month+monthDay+hour+minute+second;

}