为什么我不能通过按钮获得我的当前位置

Question

我真正需要做的是当我按位置按钮是为了获得我当前的位置并显示它像一个地址在编辑文本没有地图..但它保持给我NULL POINTER EXCEPTION ..为什么？

public class PersonalInfo extends Activity{ 
    private GoogleMap googleMap; 
    Geocoder geocoder; 
    EditText addressnew; 
    GPSTracker gps; 
    @Override 
     protected void onCreate(Bundle savedInstanceState) { 
      super.onCreate(savedInstanceState); 
      this.requestWindowFeature(Window.FEATURE_NO_TITLE); 
      setContentView(R.layout.personal_info); 
      EditText name=(EditText)findViewById(R.id.edittext1); 
      EditText mobile=(EditText)findViewById(R.id.edittext2); 
      addressnew=(EditText)findViewById(R.id.editText3); 
      Button location=(Button)findViewById(R.id.button1); 
      Button send=(Button)findViewById(R.id.button2); 


      location.setOnClickListener(new OnClickListener() { 

      @Override 
      public void onClick(View v) { 


        gps = new GPSTracker(PersonalInfo.this); 

        // check if GPS enabled 
        if (gps.canGetLocation()) { 
        //enable my location 
        googleMap.setMyLocationEnabled(true); 
        //get location object 
        LocationManager locationManager=(LocationManager)getSystemService(LOCATION_SERVICE); 
        //to retrive provider 
        Criteria criteria = new Criteria(); 

        String provider = locationManager.getBestProvider(criteria, true); 
        //get current location 

        Location mylocation=locationManager.getLastKnownLocation(provider); 
        //set map type 
        //googleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL); 
        double latitude = mylocation.getLatitude(); 
        double longitude = mylocation.getLongitude(); 
        LatLng latlng=new LatLng(latitude,longitude); 


        Toast.makeText(PersonalInfo.this, latitude+" "+longitude, Toast.LENGTH_LONG).show(); 

        List<Address> addresses; 
        geocoder = new Geocoder(PersonalInfo.this, Locale.getDefault()); 
        try{ 
         addresses = geocoder.getFromLocation(latitude, longitude, 1); 
         String address = addresses.get(0).getAddressLine(0); 
         String city = addresses.get(0).getAddressLine(1); 
         String country = addresses.get(0).getAddressLine(2); 
         String cities=addresses.get(0).getAdminArea(); 
         Log.e("address",addresses+""); 
         Log.e("address",address+""); 
         Log.e("city",cities+""); 
         Log.e("country",city+""); 
         addressnew.setText("your current location is: "+city+""+","+cities+""+","+address+""); 
         //String uri = "http://maps.google.com/maps?saddr=" + mylocation.getLatitude()+","+mylocation.getLongitude(); 

         //Uri path= Uri.parse(uri); 




        } catch (IOException e) { 
         // TODO Auto-generated catch block 
         e.printStackTrace(); 
        } 
        } 
        else{ 
         Toast.makeText(PersonalInfo.this, "gps is not enabled", Toast.LENGTH_LONG).show(); 
        } 

      } 
     }); 
    } 

} 

这里是logcat的：

FATAL EXCEPTION: main 
java.lang.NullPointerException 
at adapter.PersonalInfo$1.onClick(PersonalInfo.java:60) 
at android.view.View.performClick(View.java:3530) 
at android.view.View$PerformClick.run(View.java:14227) 
at android.os.Handler.handleCallback(Handler.java:605) 

Answer 1

要获取LocationManager并要求位置更新，请在oncreate（）中使用这些行;

mLocationManager = (LocationManager) getSystemService(LOCATION_SERVICE); 
mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 
      0, mLocationListener); 

，然后用它来获取设备的当前经纬度..

private final LocationListener mLocationListener = new LocationListener() { 
    @Override 
    public void onLocationChanged(final Location location) { 
     //write your code here 
    } 
}; 

也不要忘记添加所需的权限..

Answer 2

请使用下面的代码。

package com.example.loation; 

import java.util.List; 
import java.util.Locale; 

import android.annotation.SuppressLint; 
import android.app.Activity; 
import android.app.AlertDialog; 
import android.app.ProgressDialog; 
import android.content.Context; 
import android.content.DialogInterface; 
import android.location.Address; 
import android.location.Geocoder; 
import android.location.Location; 
import android.location.LocationListener; 
import android.location.LocationManager; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.util.Log; 

public class GettingLocation extends Activity { 

    private Double dbllatitude, dbllongitude; 
    private LocationManager myLocationManager; 
    private LocationListener myLocationListener; 
    Geocoder geocoder; 
    private LocationControl locationControlTask; 
    private boolean hasLocation = false; 
    protected Activity Activity; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     // TODO Auto-generated method stub 
     super.onCreate(savedInstanceState); 
     this.Activity = this; 
     GetLocation(); 
    } 

    private void GetLocation() { 

     myLocationManager = (LocationManager) Activity.getSystemService(Context.LOCATION_SERVICE); 
     myLocationListener = new MyLocationListener(); 
     myLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, myLocationListener); 
     // getlon.setText("Stop"); 
     if (!myLocationManager.isProviderEnabled(android.location.LocationManager.GPS_PROVIDER)) { 
      displayalert(); 
     } else { 
      locationControlTask = new LocationControl(); 
      locationControlTask.execute(); 
     } 
    } 

    public class MyLocationListener implements LocationListener { 
     public void onLocationChanged(Location argLocation) { 
      if (argLocation != null) { 
       dbllatitude = argLocation.getLatitude(); 
       dbllongitude = argLocation.getLongitude(); 
       hasLocation = true; 
      } 
     } 

     public void onProviderDisabled(String provider) {} 

     public void onProviderEnabled(String provider) {} 

     public void onStatusChanged(String provider, int status, Bundle arg2) {} 
    }; 

    @SuppressLint("NewApi") 
    private class LocationControl extends AsyncTask<Activity, Void, Void> { 
     private final ProgressDialog dialog = new ProgressDialog(Activity); 

     protected void onPreExecute() { 
      this.dialog.setMessage("Getting Location..........."); 
      this.dialog.setButton("Cancel", new DialogInterface.OnClickListener() { 
       public void onClick(DialogInterface dialog, int which) { 
        dialog.dismiss(); 
        hasLocation = true; 
       } 
      }); 
      this.dialog.show(); 
     } 

     protected Void doInBackground(Activity... params) { 
      while (!hasLocation) { 
       try { 
        Thread.sleep(1000); 
       } catch (InterruptedException e) { 
        e.printStackTrace(); 
       } 
      } 
      ; 
      return null; 
     } 

     protected void onPostExecute(final Void unused) { 
      if (this.dialog.isShowing()) { 
       this.dialog.dismiss(); 
      } 

      if (dbllatitude != null && dbllongitude != null && dbllatitude != 0.0 && dbllongitude != 0.0) { 
       try { 
        // Write your address code here 
        List<Address> addresses; 
        geocoder = new Geocoder(GettingLocation.this, Locale.getDefault()); 
        addresses = geocoder.getFromLocation(dbllatitude, dbllongitude, 1); 
        String address = addresses.get(0).getAddressLine(0); 
        String city = addresses.get(0).getAddressLine(1); 
        String country = addresses.get(0).getAddressLine(2); 
        String cities = addresses.get(0).getAdminArea(); 
        Log.e("address", addresses + ""); 
        Log.e("address", address + ""); 
        Log.e("city", cities + ""); 
        Log.e("country", city + ""); 

       } catch (Exception e) { 
        System.out.println("Error:::::::" + e.getMessage()); 
       } 
      } else { 
       displayalert1(); 
      } 
     } 

    } 

    public void displayalert1() { 
     AlertDialog.Builder builder = new AlertDialog.Builder(Activity); 
     builder.setMessage("Location not found. Do you want to try again?").setCancelable(false).setPositiveButton("OK", new DialogInterface.OnClickListener() { 
      public void onClick(DialogInterface dialog, int id) { 
       hasLocation = false; 
       locationControlTask = new LocationControl(); 
       locationControlTask.execute(); 
      } 
     }); 
     builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() { 
      public void onClick(DialogInterface dialog, int id) { 

      } 
     }); 
     builder.show(); 
    } 

    private void displayalert() { 
     AlertDialog.Builder builder = new AlertDialog.Builder(Activity); 
     builder.setMessage("GPS is turned off ,Please Enable GPS").setCancelable(false).setPositiveButton("OK", new DialogInterface.OnClickListener() { 
      public void onClick(DialogInterface dialog, int id) { 

      } 
     }); 
     builder.show(); 

    } 

}