Question

如何在执行AsyncTask之前检查网络信号强度。

例如，如果用户的电话没有互联网或不稳定的连接，则应弹出一个Toast，通知用户他/她的连接较弱。如果用户的手机具有强大或稳定的连接，则会执行asynctask。

PS。

我所说的就像这种asynctask

class AttemptGetData extends AsyncTask<String, String, String>{
        String ID = att_id.toString();
        String Stud_id = stud_no.toString();
        String remarks = RadioAttBtn.getText().toString();

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(AddStudentAttendance.this);
            pDialog.setMessage("In Progress...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();

        }

        @Override
        protected String doInBackground(String... params) {
            List<NameValuePair> mList = new ArrayList<NameValuePair>();
            mList.add(new BasicNameValuePair("att_list_id", ID));
            mList.add(new BasicNameValuePair("student_no", Stud_id));
            mList.add(new BasicNameValuePair("remark", remarks));

            Log.d("starting", "fetch");

            JSONObject json = jsonParser.makeHttpRequest(url1, "POST", mList);

            try {
                verify = json.getString("Message");
                return verify;
            }catch (JSONException e){
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            pDialog.dismiss();
            if (s != null){
                Toast.makeText(getApplicationContext(), verify, Toast.LENGTH_LONG).show();
            }
        }
    }

Answer 1

WifiManager wifiManger= (WifiManager) getActivity().getSystemService(Context.WIFI_SERVICE); 
// in Activity replace getActivity() by Context in above line
WifiInfo wifiInfo = wifiManger.getConnectionInfo();
int speedMbps = wifiInfo.getLinkSpeed();
int myspeed=2000;  //mention your speed 
if(speedMbps>2000)
{
   // start  AsyncTask
}
else
{
// your Toast message for weak connection 
}

Answer 2

我建议您创建一个定期执行的IntentService并连接到httpbin.org等已知网址。 ConnectivityManager会告诉您设备是否已连接到WiFi或移动数据，但不会告诉您是否有实际可用的互联网连接。

import android.app.IntentService;
import android.content.Intent;

import com.squareup.otto.Bus;

import java.io.IOException;

import chat.example.app.App;
import chat.example.app.events.NetworkStatusEvent;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

/**
 * IntentService is a base class for Services that handle asynchronous requests (expressed as Intents) on demand.
 * Our app uses this service to find out if we have internet connection or not.
 *
 * Why do we prefer this approach over using ConnectivityManager?
 * This is because having an active network interface doesn't guarantee that a particular networked
 * service is available. Network issues, server downtime, low signal, captive portals, content filters
 * and the like can all prevent your app from reaching a server.
 * For instance you can't tell for sure if your app can reach Twitter until you receive a valid response
 * from the Twitter service.
 * Source: http://stackoverflow.com/questions/4238921/detect-whether-there-is-an-internet-connection-available-on-android
 *
 * We will use https://httpbin.org/ to check for network connectivity
 * httpbin(1): HTTP Request & Response Service
 *
 */
public class NetworkStatusService extends IntentService{
    private static final String url = "https://httpbin.org/ip";
    private static final String TAG = "NetworkStatusService";
    //----------------------------------------------------------------------------------------------
    public NetworkStatusService(){
        super(TAG);
    }
    //----------------------------------------------------------------------------------------------
    @Override
    protected void onHandleIntent(Intent intent) {
        Logger.d(TAG,"NetworkStatusService Invoked");
        Bus bus = App.getInstance().getEventBus();
        bus.register( this );
        NetworkStatusEvent status = new NetworkStatusEvent();
        try{
            if( makeRequest().isSuccessful() ){
                Logger.d(TAG,"Network Available");
                status.isAvailable = true;
                bus.post( status );
            }else{
                Logger.d(TAG,"Network Unavailable");
                status.isAvailable = false;
                bus.post( status );
            }
        }catch(IOException e){
            Logger.d(TAG,"Network Unavailable");
            bus.post( status );
        }finally{
            bus.unregister( this );
        }
    }
    //----------------------------------------------------------------------------------------------
    private Response makeRequest() throws IOException {
        OkHttpClient client = App.getInstance().getOkHttpClient();
        Request request = new Request.Builder()
                .url(url)
                .build();
        return client.newCall( request ).execute();
    }
    //----------------------------------------------------------------------------------------------
}

这是我使用Otto事件总线和OkHttp互联网库的代码。

Android：在执行asynctask之前检查网络信号强度

2 个答案: