java.lang.IllegalArgumentException:provider == null

时间:2013-08-09 10:24:05

标签: android-maps-v2

我咨询了许多答案,但没有得到解决方案。当我禁用GPS时出现此错误。如果启用GPS而不是app正常运行。如果我最初禁用GPS或在运行中途停用应用程序崩溃。我希望在禁用GPS时弹出警报对话框。

MainActivity.java

    package com.project.locationinfofinder;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.json.JSONObject;

import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.DialogInterface.OnClickListener;
import android.graphics.Color;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.util.Log;
import android.view.Menu;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.GoogleMap.OnMapClickListener;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.maps.model.PolylineOptions;


public class MainActivity extends FragmentActivity implements LocationListener {

    GoogleMap mGoogleMap;
    ArrayList<LatLng> mMarkerPoints;
    double mLatitude=0;
    double mLongitude=0;

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

        // Getting Google Play availability status
        int status = GooglePlayServicesUtil.isGooglePlayServicesAvailable(getBaseContext());

        if(status!=ConnectionResult.SUCCESS){ // Google Play Services are not available

            int requestCode = 10;
            Dialog dialog = GooglePlayServicesUtil.getErrorDialog(status, this, requestCode);
            dialog.show();

        }else { // Google Play Services are available

            // Initializing 
            mMarkerPoints = new ArrayList<LatLng>();

            // Getting reference to SupportMapFragment of the activity_main
            SupportMapFragment fm = (SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map);

            // Getting Map for the SupportMapFragment
            mGoogleMap = fm.getMap();

            // Enable MyLocation Button in the Map
            mGoogleMap.setMyLocationEnabled(true);


            // Getting LocationManager object from System Service LOCATION_SERVICE
            LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

            // Creating a criteria object to retrieve provider
            Criteria criteria = new Criteria();

            // Getting the name of the best provider
            String provider = locationManager.getBestProvider(criteria, true);

            // Getting Current Location From GPS

            Location location = locationManager.getLastKnownLocation(provider);

            if(location!=null){
                onLocationChanged(location);
            }

            locationManager.requestLocationUpdates(provider, 20000, 0, this);           

            // Setting onclick event listener for the map
            mGoogleMap.setOnMapClickListener(new OnMapClickListener() {

                @Override
                public void onMapClick(LatLng point) {

                    // Already map contain destination location 
                    if(mMarkerPoints.size()>1){

                        FragmentManager fm = getSupportFragmentManager();   
                        mMarkerPoints.clear();
                        mGoogleMap.clear();
                        LatLng startPoint = new LatLng(mLatitude, mLongitude);
                        drawMarker(startPoint);
                    }

                    drawMarker(point);

                    // Checks, whether start and end locations are captured
                    if(mMarkerPoints.size() >= 2){                  
                        LatLng origin = mMarkerPoints.get(0);
                        LatLng dest = mMarkerPoints.get(1);

                        // Getting URL to the Google Directions API
                        String url = getDirectionsUrl(origin, dest);                

                        DownloadTask downloadTask = new DownloadTask();

                        // Start downloading json data from Google Directions API
                        downloadTask.execute(url);
                    }                   
                }
            });         
        }       
    }

    private String getDirectionsUrl(LatLng origin,LatLng dest){

        // Origin of route
        String str_origin = "origin="+origin.latitude+","+origin.longitude;

        // Destination of route
        String str_dest = "destination="+dest.latitude+","+dest.longitude;          

        // Sensor enabled
        String sensor = "sensor=false";         

        // Building the parameters to the web service
        String parameters = str_origin+"&"+str_dest+"&"+sensor;

        // Output format
        String output = "json";

        // Building the url to the web service
        String url = "https://maps.googleapis.com/maps/api/directions/"+output+"?"+parameters;      

        return url;
    }

    /** A method to download json data from url */
    private String downloadUrl(String strUrl) throws IOException{
        String data = "";
        InputStream iStream = null;
        HttpURLConnection urlConnection = null;
        try{
                URL url = new URL(strUrl);

                // Creating an http connection to communicate with url 
                urlConnection = (HttpURLConnection) url.openConnection();

                // Connecting to url 
                urlConnection.connect();

                // Reading data from url 
                iStream = urlConnection.getInputStream();

                BufferedReader br = new BufferedReader(new InputStreamReader(iStream));

                StringBuffer sb  = new StringBuffer();

                String line = "";
                while( ( line = br.readLine())  != null){
                        sb.append(line);
                }

                data = sb.toString();

                br.close();

        }catch(Exception e){
                Log.d("Exception while downloading url", e.toString());
        }finally{
                iStream.close();
                urlConnection.disconnect();
        }
        return data;
     }



    /** A class to download data from Google Directions URL */
    private class DownloadTask extends AsyncTask<String, Void, String>{         

        // Downloading data in non-ui thread
        @Override
        protected String doInBackground(String... url) {

            // For storing data from web service
            String data = "";

            try{
                // Fetching the data from web service
                data = downloadUrl(url[0]);
            }catch(Exception e){
                Log.d("Background Task",e.toString());
            }
            return data;        
        }

        // Executes in UI thread, after the execution of
        // doInBackground()
        @Override
        protected void onPostExecute(String result) {           
            super.onPostExecute(result);            

            ParserTask parserTask = new ParserTask();

            // Invokes the thread for parsing the JSON data
            parserTask.execute(result);

        }       
    }

    /** A class to parse the Google Directions in JSON format */
    private class ParserTask extends AsyncTask<String, Integer, List<List<HashMap<String,String>>> >{

        // Parsing the data in non-ui thread        
        @Override
        protected List<List<HashMap<String, String>>> doInBackground(String... jsonData) {

            JSONObject jObject; 
            List<List<HashMap<String, String>>> routes = null;                     

            try{
                jObject = new JSONObject(jsonData[0]);
                DirectionsJSONParser parser = new DirectionsJSONParser();

                // Starts parsing data
                routes = parser.parse(jObject);    
            }catch(Exception e){
                e.printStackTrace();
            }
            return routes;
        }

        // Executes in UI thread, after the parsing process
        @Override
        protected void onPostExecute(List<List<HashMap<String, String>>> result) {
            ArrayList<LatLng> points = null;
            PolylineOptions lineOptions = null;

            // Traversing through all the routes
            for(int i=0;i<result.size();i++){
                points = new ArrayList<LatLng>();
                lineOptions = new PolylineOptions();

                // Fetching i-th route
                List<HashMap<String, String>> path = result.get(i);

                // Fetching all the points in i-th route
                for(int j=0;j<path.size();j++){
                    HashMap<String,String> point = path.get(j);                 

                    double lat = Double.parseDouble(point.get("lat"));
                    double lng = Double.parseDouble(point.get("lng"));
                    LatLng position = new LatLng(lat, lng); 

                    points.add(position);                       
                }

                // Adding all the points in the route to LineOptions
                lineOptions.addAll(points);
                lineOptions.width(2);
                lineOptions.color(Color.RED);   

            }

            // Drawing polyline in the Google Map for the i-th route
            mGoogleMap.addPolyline(lineOptions);                            
        }           
    }   


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

    private void drawMarker(LatLng point){
        mMarkerPoints.add(point);

        // Creating MarkerOptions
        MarkerOptions options = new MarkerOptions();

        // Setting the position of the marker
        options.position(point);

        //For the start location, the color of marker is GREEN and
         // for the end location, the color of marker is RED.

        if(mMarkerPoints.size()==1){
            options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN));
        }else if(mMarkerPoints.size()==2){
            options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED));
        }

        // Add new marker to the Google Map Android API V2
        mGoogleMap.addMarker(options);      
    }

    @Override
    public void onLocationChanged(Location location) {
        // Draw the marker, if destination location is not set
        if(mMarkerPoints.size() < 2){

            mLatitude = location.getLatitude();
            mLongitude = location.getLongitude();
            LatLng point = new LatLng(mLatitude, mLongitude);

            mGoogleMap.moveCamera(CameraUpdateFactory.newLatLng(point));
            mGoogleMap.animateCamera(CameraUpdateFactory.zoomTo(12));        

            drawMarker(point);          
        } 

    }


    @Override
    public void onProviderDisabled(String provider) {
        // TODO Auto-generated method stub      
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("GPS is disabled");
        builder.setCancelable(false);
        builder.setPositiveButton("Enable GPS", new OnClickListener() {

            @Override
            public void onClick(DialogInterface dailog, int which) {
                // TODO Auto-generated method stub
                Intent StartGPS = new Intent(
                        android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                startActivity(StartGPS);

            }
        });
        builder.setNegativeButton("Cancel", new OnClickListener() {

            @Override
            public void onClick(DialogInterface dailog, int which) {
                // TODO Auto-generated method stub
                dailog.cancel();
            }
        });
        AlertDialog alert = builder.create();
        alert.show();

    }

    @Override
    public void onProviderEnabled(String provider) {
        // TODO Auto-generated method stub      
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub      
    }   
}

logcat的

08-09 15:42:21.718: E/AndroidRuntime(21516): FATAL EXCEPTION: main
08-09 15:42:21.718: E/AndroidRuntime(21516): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.project.locationinfofinder/com.project.locationinfofinder.MainActivity}: java.lang.IllegalArgumentException: provider==null
08-09 15:42:21.718: E/AndroidRuntime(21516):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at android.os.Handler.dispatchMessage(Handler.java:99)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at android.os.Looper.loop(Looper.java:130)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at android.app.ActivityThread.main(ActivityThread.java:3687)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at java.lang.reflect.Method.invokeNative(Native Method)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at java.lang.reflect.Method.invoke(Method.java:507)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:842)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at dalvik.system.NativeStart.main(Native Method)
08-09 15:42:21.718: E/AndroidRuntime(21516): Caused by: java.lang.IllegalArgumentException: provider==null
08-09 15:42:21.718: E/AndroidRuntime(21516):    at android.location.LocationManager.requestLocationUpdates(LocationManager.java:441)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at com.project.locationinfofinder.MainActivity.onCreate(MainActivity.java:105)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-09 15:42:21.718: E/AndroidRuntime(21516):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
08-09 15:42:21.718: E/AndroidRuntime(21516):    ... 11 more

1 个答案:

答案 0 :(得分:0)

如果只是检查你是否有任何提供者呢?

if (provider != null) {
    locationManager.requestLocationUpdates(provider, 20000, 0, this);           
} else {
    showDialog(...);
}