我有辦法每 15 秒測試一次互聯網連接。如果設備有互聯網連接，則不需要任何東西，但如果您沒有互聯網連接，我想調用 Fragment。崩潰。如果我無法從 AsyncTask 中調用片段，我可以從 MainActivity 中調用它。我不知道怎么做。檢查InternetAsyncTask.classpublic class CheckInternetAsyncTask extends AsyncTask<Void, Integer, Boolean> {private MainActivity activity;    private Context context;    public CheckInternetAsyncTask(Context context) {        this.context = context;    }    @Override    protected Boolean doInBackground(Void... params) {        ConnectivityManager cm =                (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);        assert cm != null;        NetworkInfo activeNetwork = cm.getActiveNetworkInfo();        boolean isConnected = activeNetwork != null &&                activeNetwork.isConnected();        if (isConnected) {            try {                InetAddress ipAddr = InetAddress.getByName("google.com");                //You can replace it with your name                return !ipAddr.equals("");            } catch (Exception e) {                Log.e("TAG", "Error checking internet connection"+ e.getMessage());                return false;            }        } else {            //Log.d("TAG", "No network available!");            return false;        }    }    @Override    protected void onPostExecute(Boolean result) {        super.onPostExecute(result);        //Log.d("TAG", "result" + result);        if(result){            // do ur code            Toast.makeText(context,"Device is connected to internet.", Toast.LENGTH_LONG).show();        }        else {            Toast.makeText(context,"Device is not connected to internet!",Toast.LENGTH_LONG).show(); EthernetControlFragment ethernetControlFragment = EthernetControlFragment.newInstance();        ethernetControlFragment.show(activity.getSupportFragmentManager(), "ethernet");        ethernetControlFragment.setCancelable(false);        }    }}