android程序运行空指针有关问题

android程序运行空指针问题。
调试程序报错空指针。
我是在网上找别人的代码。

Mylocation.java
 
  

package com.swift.mylocation;
 
import java.io.IOException;
 import java.util.List;
 import java.util.Locale;
 
import android.app.PendingIntent;
 
import android.content.Context;
 import android.content.Intent;
 
import android.location.Address;
 import android.location.Criteria;
 import android.location.Geocoder;
 import android.location.Location;
 import android.location.LocationListener;
 import android.location.LocationManager;
 import android.os.Bundle;
 
 
 
import android.widget.TextView;
 import android.widget.Toast;
 
import com.google.android.maps.GeoPoint;
 import com.google.android.maps.MapActivity;
 import com.google.android.maps.MapController;
 import com.google.android.maps.MapView;
 import com.google.android.maps.Overlay;
 import com.swift.mylocation.R;
 
public class Mylocation extends MapActivity {
 
 MapController mapController;
  List<Overlay> overlays;
  MyPositionOverlay positionOverlay;
  LocationManager locationManager;
  MapView myMapView;
 
 final String PROXIMITY_ALERT = new String(
  "android.intent.action.proximityalert");
 
 @SuppressWarnings("deprecation")
  @Override
  public void onCreate(Bundle icicle) {
  super.onCreate(icicle);
  setContentView(R.layout.main);
 
  myMapView = (MapView) findViewById(R.id.myMapView);
 
  mapController = myMapView.getController();
 
  myMapView.setSatellite(true);
  myMapView.setStreetView(true);
  myMapView.displayZoomControls(false);
 
  mapController.setZoom(17);
 
  positionOverlay = new MyPositionOverlay();
  overlays = myMapView.getOverlays();
  overlays.add(positionOverlay);
 
  Criteria criteria = new Criteria();
  criteria.setAccuracy(Criteria.ACCURACY_FINE);
  criteria.setAltitudeRequired(true);
  criteria.setBearingRequired(false);
  criteria.setCostAllowed(false);
  criteria.setPowerRequirement(Criteria.POWER_LOW);
  locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
 
  String provider = locationManager.getBestProvider(criteria, true);
 
  Location location = locationManager.getLastKnownLocation(provider);
 
  updateWithNewLocation(location);
 
  locationManager.requestLocationUpdates(provider, 2000, 10,
  locationListener);
  
  setProximityAlert();
 
 }
 
 private final LocationListener locationListener = new LocationListener() {
  @Override
  public void onLocationChanged(Location location) {
  updateWithNewLocation(location);
  }
 
  @Override
  public void onProviderDisabled(String provider) {
  updateWithNewLocation(null);
  }
 
  @Override
  public void onProviderEnabled(String provider) {
  }
 
  @Override
  public void onStatusChanged(String provider, int status, Bundle extras) {
  }
  };
 
 
  
 
 void setProximityAlert() {
   
  double lat = 31.620356666666666;
  double lng = 121.38631333333333;