android - 如何在 AsyncTask 中执行函数？

Question

我必须在 AsyncTask 中使用 directions() 函数来避免在 UI 线程上进行网络处理。我无法执行此操作。 我的代码是

    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;
    }

}

Answer 1

大概是这样？

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();
        }
    }

}