Passing GPS LonLat from Android GPS to WebPage (javascript)

Question

I have the following code but the lon/lat seems to be returning null;

package com.domain.www;

import android.app.Activity;
import android.content.Context;
import android.content.pm.ActivityInfo;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.location.Criteria;
import android.os.Bundle;
import android.webkit.WebView;
import android.webkit.WebViewClient;

public class WebMapActivity extends Activity implements LocationListener {

    private static final String MAP_URL = "http://www.yahoo.com/";
    private WebView webView;
    private Location mostRecentLocation;

    @Override
    /** Called when the activity is first created. */
    public void onCreate(Bundle savedInstanceState) {
        try {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);
            getLocation();
            setupWebView();
            this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    /** Sets up the WebView object and loads the URL of the page **/
    private void setupWebView() {
        /*
            final String centerURL = "javascript:centerAt("
                    + mostRecentLocation.getLatitude() + ","
                    + mostRecentLocation.getLongitude() + ")"; */

            webView = (WebView) findViewById(R.id.webview);
            webView.getSettings().setJavaScriptEnabled(true);

            webView.setWebViewClient(new WebViewClient() {
                @Override
                public void onPageFinished(WebView view, String url)
                {
                    String jsCode = "javascript:alert('" + getMostRecentLocation("lon") + "')";
                    webView.loadUrl(jsCode.toString());
                }
            });


            webView.loadUrl(MAP_URL);
    }

    /**
     * The Location Manager manages location providers. This code searches for
     * the best provider of data (GPS, WiFi/cell phone tower lookup, some other
     * mechanism) and finds the last known location.
     **/
    private void getLocation() {
        LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        Criteria criteria = new Criteria();
        criteria.setAccuracy(Criteria.ACCURACY_FINE);
        String provider = locationManager.getBestProvider(criteria, true);

        // In order to make sure the device is getting location, request
        // updates. locationManager.requestLocationUpdates(provider, 1, 0,
        // this);
        //locationManager.requestLocationUpdates(provider, 1, 0, this);
        setMostRecentLocation(locationManager.getLastKnownLocation(provider));
    }

    /** Sets the mostRecentLocation object to the current location of the device **/
    @Override
    public void onLocationChanged(Location location) {
        setMostRecentLocation(location);
    }

    /**
     * The following methods are only necessary because WebMapActivity
     * implements LocationListener
     **/
    @Override
    public void onProviderDisabled(String provider) {
    }

    @Override
    public void onProviderEnabled(String provider) {
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }

    /**
     * @param mostRecentLocation the mostRecentLocation to set
     */
    public void setMostRecentLocation(Location mostRecentLocation) {
        this.mostRecentLocation = mostRecentLocation;
    }

    /**
     * @return the mostRecentLocation
     */
    public double getMostRecentLocation(String lonLat) {
        double gValue = 0.00;
        try
        {
        Location xx = this.mostRecentLocation;  //Used as a breakpoint
        if(lonLat == "lat") gValue = this.mostRecentLocation.getLatitude();
        if(lonLat == "lon") gValue = this.mostRecentLocation.getLongitude();        

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

        return gValue;  
    }

}

Ignore the URL bit that would be a page with a google map on it; but for debugging purposes I'd prefer it to just spit out an alert with the values in it.

Any ideas whats wrong? Target Emulators (Google API 1.5 API(3))

Thanks

Answer 1

The reason for the 0,0 latitude and longitude is that you don't have a latitude or longitude. You have done nothing in your code to get a location -- getLastKnownLocation() only works if there is something else in your code requesting location updates.

Here is a sample project that does what you want, either by pulling (a la Mr. Nurik's addJavascriptInterface() recommendation), or by pushing (using the javascript: notation).