Show ProgressDialog in a Service class

问题

I am using a Service to connect to a network using a AsyncTask. I want to show a ProgressDialog till the app is connected to the network. But how can I do this?

My Service looks like this:

package de.bertrandt.bertrandtknx;

import tuwien.auto.calimero.link.KNXNetworkLinkIP;
import tuwien.auto.calimero.process.ProcessCommunicator;
import de.bertrandt.bertrandtknx.Controls.OnOff;
import android.app.ProgressDialog;
import android.app.Service;
import android.content.Intent;
import android.net.wifi.WifiInfo;
import android.net.wifi.WifiManager;
import android.os.AsyncTask;
import android.os.IBinder;
import android.widget.Toast;


public class ConnectionService  extends Service {

    public static KNXNetworkLinkIP m_netLinkIp = null;
    private static ProcessCommunicator m_pc = null;


    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onCreate() {
       //code to execute when the service is first created
        new Connect().execute();
    }

    @Override
    public void onDestroy() {
       //code to execute when the service is shutting down
        new Disconnect().execute();
    }

    public void onStartCommand(Intent intent, int startid) {
       //code to execute when the service is starting up
    }


    /**
     * GetIPAddress Async
     * */
    public String getIpAddr() {
           WifiManager wifiManager = (WifiManager) getSystemService(WIFI_SERVICE);
           WifiInfo wifiInfo = wifiManager.getConnectionInfo();
           int ip = wifiInfo.getIpAddress();

           String ipString = String.format(
           "%d.%d.%d.%d",
           (ip & 0xff),
           (ip >> 8 & 0xff),
           (ip >> 16 & 0xff),
           (ip >> 24 & 0xff));

           return ipString.toString();
    }

    /**
     * Connect Async
     * */
    private class Connect extends AsyncTask<String, Void, String> {
          ProgressDialog dialog;
          boolean ok;
          @Override
          protected String doInBackground(String... params) {
              try {
                  //get local IP address
                  String ipAddress = getIpAddr();
                  System.out.println("WiFi address is " + ipAddress);

                  m_netLinkIp = Calimero.Util.connect(ipAddress, "192.168.0.2");

                  if (m_netLinkIp == null){

                      System.out.println("Can not connect to Demobard");
                      ok = false;
                  }
                  else{
                      System.out.println("Connected to Demoboard");
                      ok = true;

                      }
               } catch (Exception e) {         
                   e.printStackTrace(); 
               }
               return null;
          }      

          @Override
          protected void onPostExecute(String result) { 
            //dialog.dismiss();
            Toast.makeText(getApplicationContext(),
                    "Verbindung mit Demoboard " +
                            ((ok == true) ? "hergestellt" : "fehlgeschlagen"), Toast.LENGTH_LONG).show();
            if(ok == false){
                //show reconnect dialog
                //reconnect_dialog();
            }
          }

          @Override
          protected void onPreExecute() {
           // Setup Progress Dialog
           dialog = new ProgressDialog(OnOff.this);
           dialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
           dialog.setMessage("Bitte warten, verbinde mit KNX-Board");
           dialog.setIndeterminate(true);
           dialog.show();*/
          }
    }

    /**
     * Disconnect Async
     * */
    private class Disconnect extends AsyncTask<String, Void, String> {
          @Override
          protected String doInBackground(String... params) {
                    try {
                        Calimero.Util.disconnect(m_netLinkIp);
                    } catch (Exception e) {
                        e.printStackTrace(); 
                    }
                return null;
          }      

    }

}

Of course this code makes problems how can I get the context of the activity which starts the Service?

The Dialog should be shown in the activity which starts the Service until the app is connected.

回答1:

So a service is NOT the UI you have to use the observer pattern. Your activity have to register a listener in the service so that the service can inform the activity for special events (like start loading or finish loading).

You have to add following intercae into your service class:

    public interface serviceObserver {
        public void startLoading();
        public void stopLoading();
    }

Your activity has to implement serviceObserver. Your service has to store a instance from serviceObserver which is created in the activity. If your service is running without your activity i recommend to use broadcast receiver for communication.

来源：https://stackoverflow.com/questions/13347253/show-progressdialog-in-a-service-class