how to do functions in an AsyncTask?

Question

I have to use directions() function in an AsyncTask to avoid network processing on the UI thread.i'm unable to do this thing. MY code is

    public class MainActivity extends MapActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        MapView mapView = (MapView) findViewById(R.id.mapview); //or you can declare it directly with the API key
        Route route = directions(new GeoPoint((int)(26.2*1E6),(int)(50.6*1E6)), new GeoPoint((int)(26.3*1E6),(int)(50.7*1E6)));
        RouteOverlay routeOverlay = new RouteOverlay(route, Color.BLUE);
        mapView.getOverlays().add(routeOverlay);
        mapView.invalidate();
    }

    private Route directions(final GeoPoint start, final GeoPoint dest) {
        Parser parser;
        //https://developers.google.com/maps/documentation/directions/#JSON <- get api
        String jsonURL = "http://maps.googleapis.com/maps/api/directions/json?";
        final StringBuffer sBuf = new StringBuffer(jsonURL);
        sBuf.append("origin=");
        sBuf.append(start.getLatitudeE6()/1E6);
        sBuf.append(',');
        sBuf.append(start.getLongitudeE6()/1E6);
        sBuf.append("&destination=");
        sBuf.append(dest.getLatitudeE6()/1E6);
        sBuf.append(',');
        sBuf.append(dest.getLongitudeE6()/1E6);
        sBuf.append("&sensor=true&mode=driving");
        parser = new GoogleParser(sBuf.toString());
        Route r =  parser.parse();
        return r;
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    @Override
    protected boolean isRouteDisplayed() {
        // TODO Auto-generated method stub
        return false;
    }

}

I'm not sure I'm reading your code right but I'm assuming you want directions to be the AsyncTask. Is that correct? — James Jones, Mar 13 '13 at 04:56
http://developer.android.com/reference/android/os/AsyncTask.html — Jay Mayu, Mar 13 '13 at 05:02

score 1 · Answer 1 · answered Mar 13 '13 at 04:58

Perhaps like this?

public class MainActivity extends MapActivity {

    private MapView mapView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mapView = (MapView) findViewById(R.id.mapview); //or you can declare it directly with the API key
        // You can execute it at onCreate or whenever you want, for example: in a click event
        new AsyncRoutes().execute();
    }

    private Route directions(final GeoPoint start, final GeoPoint dest) {
        Parser parser;
        //https://developers.google.com/maps/documentation/directions/#JSON <- get api
        String jsonURL = "http://maps.googleapis.com/maps/api/directions/json?";
        final StringBuffer sBuf = new StringBuffer(jsonURL);
        sBuf.append("origin=");
        sBuf.append(start.getLatitudeE6()/1E6);
        sBuf.append(',');
        sBuf.append(start.getLongitudeE6()/1E6);
        sBuf.append("&destination=");
        sBuf.append(dest.getLatitudeE6()/1E6);
        sBuf.append(',');
        sBuf.append(dest.getLongitudeE6()/1E6);
        sBuf.append("&sensor=true&mode=driving");
        parser = new GoogleParser(sBuf.toString());
        Route r =  parser.parse();
        return r;
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    @Override
    protected boolean isRouteDisplayed() {
        // TODO Auto-generated method stub
        return false;
    }

    private class AsyncRoutes extends AsyncTask<Void, Integer, Route> {

        private ProgressDialog pDialog;

        @Override
        protected void onPreExecute() {

            pDialog = new ProgressDialog(LoginActivity.this);
            pDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
            pDialog.setMessage("Obtaining routes...");
            pDialog.setCancelable(false);
            pDialog.show();
        }

        @Override
        protected Route doInBackground(Void... params) {

            Route route = directions(new GeoPoint((int)(26.2*1E6),(int)(50.6*1E6)), new GeoPoint((int)(26.3*1E6),(int)(50.7*1E6)));
            return route;
        }

        @Override
        protected void onPostExecute(Route route) {         

            RouteOverlay routeOverlay = new RouteOverlay(route, Color.BLUE);
            mapView.getOverlays().add(routeOverlay);
            mapView.invalidate();

            pDialog.dismiss();
        }
    }

}

thanks.I'm using below link for driving directions in android there they said just to use direction() function in asynctask but still the app was unfortunately stopped..can u pl help me. http://stackoverflow.com/questions/11745314/why-retrieving-google-directions-for-android-using-kml-data-is-not-working-anymo/11745316#11745316 — Mukul Bansal, Mar 13 '13 at 05:10
Then, please provide the LogCat output to know where the problem might be. — , Mar 13 '13 at 05:12
the log cat shows this 03-13 10:43:15.129: E/Index 0 out of range [0..0)(18918): Google JSON Parser - http://maps.googleapis.com/maps/api/directions/json?origin=26.2,50.6&destination=26.3,50.7&sensor=true&mode=driving 03-13 10:43:15.182: E/AndroidRuntime(18918): FATAL EXCEPTION: main — Mukul Bansal, Mar 13 '13 at 05:15
I think the error is in the google JSON parser link http://maps.googleapis.com/maps/api/directions/json?origin=26.2,50.6&destination=26.3,50.7&sensor=true&mode=driving Can you provide the way to correct this — Mukul Bansal, Mar 13 '13 at 05:22

codeMagic · Answer 2 · 2013-03-13T05:13:32.813

This is the basic structure of an AsyncTask

public class TalkToServer extends AsyncTask<String, String, String> {
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected void onProgressUpdate(String... values) {
        super.onProgressUpdate(values);

    }

    @Override
    protected String doInBackground(String... params) {
    //do your work here
        return something;
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
           // do something with data here-display it or send to mainactivity
}

you can do your network stuff and/or stuff that you have in directions in doInBackground() and update UI on the other methods. You can also put the directions method as a private method of your AsyncTask

Then you would call this from your MainActivity like

TalkToServer networkStuff = new TalkToServer(); //could pass params to a constructor here such as context
networkStuff.execute();

If the AsyncTask isn't an inner class of your MainActivity then you will need a constructor to receive the context from your MainActivity if you want to do UI stuff

thanks.I'm using below link for driving directions in android there they said just to use direction() function in asynctask but still the app was unfortunately stopped..can u pl help me. http://stackoverflow.com/questions/11745314/why-retrieving-google-directions-for-android-using-kml-data-is-not-working-anymo/11745316#11745316 — Mukul Bansal, Mar 13 '13 at 05:48
Yes, follow what I provided in the answer and post any/all error messages you get. Make the `AyncTask` an inner class of your `MainActivity` then either put the contents of `directions` in the `doInBackground()` or simply call the `directions` from `do"inBackground()` and make `directions` a method in your `AsyncTask class` — codeMagic, Mar 13 '13 at 12:49

James Jones · Answer 3 · 2013-03-13T13:12:06.620

Here is what I think they mean when they say you can use an AsyncTask:

public class MainActivity extends MapActivity {

private MapView mapView; 

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mapView = (MapView) findViewById(R.id.mapview); //or you can declare it directly with the API key
    RouteTask routeTask = new RouteTask(new GeoPoint((int)(26.2*1E6),(int)(50.6*1E6)), new GeoPoint((int)(26.3*1E6),(int)(50.7*1E6));
    routeTask.execute("");
}

private Route directions(final GeoPoint start, final GeoPoint dest) {
    Parser parser;
    //https://developers.google.com/maps/documentation/directions/#JSON <- get api
    String jsonURL = "http://maps.googleapis.com/maps/api/directions/json?";
    final StringBuffer sBuf = new StringBuffer(jsonURL);
    sBuf.append("origin=");
    sBuf.append(start.getLatitudeE6()/1E6);
    sBuf.append(',');
    sBuf.append(start.getLongitudeE6()/1E6);
    sBuf.append("&destination=");
    sBuf.append(dest.getLatitudeE6()/1E6);
    sBuf.append(',');
    sBuf.append(dest.getLongitudeE6()/1E6);
    sBuf.append("&sensor=true&mode=driving");
    parser = new GoogleParser(sBuf.toString());
    Route r =  parser.parse();
    return r;
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

@Override
protected boolean isRouteDisplayed() {
    // TODO Auto-generated method stub
    return false;
}

class RouteTask extends AsyncTask<String, Void, String> {
    private GeoPoint start;
    private GeoPoint dest;
    private Route route;

    public RouteTask(GeoPoint start, GeoPoint dest) {
        this.start = start;
        this.dest = dest;
    }

    protected String doInBackground(String... strings) {
        //runs the directions method in a background thread.
        route = directions(start, dest);
        return "Started";
    }

    @Override
    protected void onPostExecute(String s) {
        //Updates the UI on the main/UI thread (post execute is called on the main/UI thread).
        RouteOverlay routeOverlay = new RouteOverlay(route, Color.BLUE);
        mapView.getOverlays().add(routeOverlay);
        mapView.invalidate();
    }
}

}

This will run the directions method on a background thread and update the map on the main/UI thread. AS a general practice for all programing languages you should do UI work on the thread that draws to the screen (main/UI thread in this case).

This should do what you need it to.

thanks.I'm using below link for driving directions in android there they said just to use direction() function in asynctask but still the app was unfortunately stopped..can u pl help me. http://stackoverflow.com/questions/11745314/why-retrieving-google-directions-for-android-using-kml-data-is-not-working-anymo/11745316#11745316 — Mukul Bansal, Mar 13 '13 at 05:47

how to do functions in an AsyncTask?

3 Answers3

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