如何在Android硬盘而不是SD卡上创建持久文本文件

Question

After reading 7 years of SO questions about how to get an unique device id from and Android device(and how one really should rethink not to do that), I think that creating a file on the device(not on SD card and not where it get wiped during uninstall or user wipe data) is a good approche.

But how to save this file and is it possible?

I have this code but it will save it to the app internal storage dir only

public synchronized static String applicationId() {
    if (sID == null) {
        File file = new File(Application.getInstance().getFilesDir(), Application.getInstance().getString(R.string.application_id_key));
        try {
            if (!file.exists())
                writeApplicationIdFile(file);
            sID = readApplicationIdFile(file);
        } catch (Exception e) {
            throw new RuntimeException("Writing ApplicationIdFile failed",e);
        }
    }
    return sID;
}
private static String readApplicationIdFile(File file) throws IOException {
    RandomAccessFile in = new RandomAccessFile(file, "r");
    byte[] bytes = new byte[(int) in.length()];
    in.readFully(bytes);
    in.close();
    return new String(bytes);
}

private static void writeApplicationIdFile(File file) throws IOException {
    FileOutputStream out = new FileOutputStream(file);
    out.write(UUID.randomUUID().toString().getBytes());
    out.close();
    LogManager.i("writeApplicationIdFile", "Writing ApplicationIdFile");
}

Answer 1

Might /data/local/tmp could help to you if you have got root access. In common practice this is not goot solution for mobile apps to store unique ID's. Imho, this is awful.