java - 每次打开应用程序时，在 Android sdcard0 中动态保存 .text 文件

Question

我收到了一些人的语音记录。我想给他们id。我正在尝试在 Android sdcard0 中保存一个 .txt 文件，其中包含新的 id 值。

我的意思是，我为新人打开申请。程序从 txt 文件中读取最后一个 id 值。然后给新人的id加+1。并更新.txt文件内容。

后来我关闭了应用程序。然后，我再次打开应用程序，读取最后一个 id 值，并使用 person id +1 保存另一个人的语音。我想在每次应用程序打开时动态更新 Android sdcard0 内存中的 .txt 文件 id 的内容。

我怎样才能做到这一点？请帮我。这是我的简单代码。

enter cod private String Load() {
String result = null;;
String FILE_NAME = "counter.txt";

    String baseDir = Environment.getExternalStorageDirectory().getAbsolutePath() + "/" + "Records";
    File file = new File(baseDir, FILE_NAME);

   int counter = 0;
    StringBuilder text = new StringBuilder();

    try {
        FileReader fReader = new FileReader(file);
        BufferedReader bReader = new BufferedReader(fReader);
        //.....??....

        }
        result = String.valueOf(text);
    } catch (IOException e) {
        e.printStackTrace();
    }

return result;

}

Answer 1

如果我理解正确的话，你想在每次打开应用程序时将lastid+1添加到你的文本文件中。您也想在您的 SD 卡上存储和编辑此文件!

可以通过 3 个步骤来尝试实现此目的:

1. Read from the file
2. Find the last added id
3. Write the new id to the text file

//Find the directory for the SD Card using the API
//*Don't* hardcode "/sdcard"
File sdcard = Environment.getExternalStorageDirectory();

//Get the text file
File file = new File(sdcard, "counter.txt");

//Read text from file
StringBuilder text = new StringBuilder();

try {
    BufferedReader br = new BufferedReader(new FileReader(file));
    String lastLine = "";

    while ((sCurrentLine = br.readLine()) != null) 
    {
        lastLine = sCurrentLine;
    }

    br.close();
    //Parse the string into an actual int.
    int lastId = Integer.parseInt(lastLine);


    //This will allow you to write to the file
    //the boolean true tell the FileOutputStream to append
    //instead of replacing the exisiting text
    outStream = new FileOutputStream(file, true);
    outStreamWriter = new OutputStreamWriter(outStream); 
    int newId = lastId + 1;

    //Write the newId at the bottom of the file!
    outStreamWriter.append(Integer.toString(newId));
    outStreamWriter.flush();
    outStreamWriter.close();
}
catch (IOException e) {
    //You'll need to add proper error handling here
}

写入外部存储(例如 SD 卡)需要在 Android list 中添加特殊权限，只需添加

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

这样就可以了!

有关引用资料，请查看以下链接:

How can I read a text file in Android?

how to read last line in a text file using java

android saving to SD card as text file

append text to the end of the file