如何在AsyncTask中调用fragment？

Question

我有办法每 15 秒测试一次互联网连接。如果设备有互联网连接，则不需要任何东西，但如果您没有互联网连接，我想调用 Fragment。崩溃。如果我无法从 AsyncTask 中调用片段，我可以从 MainActivity 中调用它。我不知道怎么做。检查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);        }    }}

Answer 1

activity您从未设置异步任务的属性。

你 AsyncTask 的构造函数应该是：

public CheckInternetAsyncTask(Activity activity) {

   this.context = activity.getApplicationContext();

   this.activity = activity;

}

并将您的任务称为：

new CheckInternetAsyncTask(MainActivity.this).execute();

Answer 2

在 Giorgos 代码的基础上，尝试这个小改动：

    public CheckInternetAsyncTask(AppCompatActivity activity) {

        this.context = activity.getApplicationContext();

        this.activity = activity;

    }