如何将文件读/写到网络附加存储Java Android

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

ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
if (networkInfo != null && networkInfo.isConnected()) {
    // 网络已连接
} else {
    // 网络未连接
}

File file = new File(Environment.getExternalStorageDirectory(), "file.txt");
try {
    FileInputStream fis = new FileInputStream(file);
    // 读取文件内容
    // ...
    fis.close();
} catch (IOException e) {
    e.printStackTrace();
}

File file = new File(Environment.getExternalStorageDirectory(), "file.txt");
try {
    FileOutputStream fos = new FileOutputStream(file);
    // 写入文件内容
    // ...
    fos.close();
} catch (IOException e) {
    e.printStackTrace();
}