我试图让用户输入他们想要前往的位置（地址）。一旦他们进入并点击“查找坐标”按钮，应用程序应该会自动获取位置的坐标，并且应该在点击“保存点”按钮时保存。但是当我点击“查找坐标”时，我无法获得坐标。我哪里出错了？请帮忙。提前致谢。
这是我的代码：
package com.javacodegeeks.android.lbs;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.List;
import java.util.Locale;
import android.app.Activity;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.SharedPreferences;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class ProxAlertActivity extends Activity {
Geocoder gc;
private static final long MINIMUM_DISTANCECHANGE_FOR_UPDATE = 1; // in Meters
private static final long MINIMUM_TIME_BETWEEN_UPDATE = 1000; // in Milliseconds
private static final long POINT_RADIUS = 1000; // in Meters
private static final long PROX_ALERT_EXPIRATION = -1;
private static final String POINT_LATITUDE_KEY = "POINT_LATITUDE_KEY";
private static final String POINT_LONGITUDE_KEY = "POINT_LONGITUDE_KEY";
private static final String PROX_ALERT_INTENT = "com.javacodegeeks.android.lbs.ProximityAlert";
private static final NumberFormat nf = new DecimalFormat("##.########");
private LocationManager locationManager;
private EditText latitudeEditText;
private EditText longitudeEditText;
private Button findCoordinatesButton;
private Button savePointButton;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
final EditText ed=(EditText)findViewById(R.id.point_address);
Button b1=(Button)findViewById(R.id.find_coordinates_button);
Button b2=(Button)findViewById(R.id.save_point_button);
final String to_add = ed.getText().toString();
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER,
MINIMUM_TIME_BETWEEN_UPDATE,
MINIMUM_DISTANCECHANGE_FOR_UPDATE,
new MyLocationListener()
);
findCoordinatesButton = (Button) findViewById(R.id.find_coordinates_button);
savePointButton = (Button) findViewById(R.id.save_point_button);
findCoordinatesButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
populateCoordinatesFromLastKnownLocation();
try
{
List<Address> address2=gc.getFromLocationName(to_add, 3);
if (address2 != null && address2.size() >0)
{
double lat1 = address2.get(0).getLatitude();
double lng1 = address2.get(0).getLongitude();
Toast.makeText(getBaseContext(), "Lat:" +lat1+"Long:"+lng1, Toast.LENGTH_SHORT).show();
}
}catch(Exception e)
{
e.printStackTrace();
}
}
});
savePointButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
saveProximityAlertPoint();
}
});
}
private void saveProximityAlertPoint() {
Location location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location==null) {
Toast.makeText(this, "No last known location. Aborting...", Toast.LENGTH_LONG).show();
return;
}
saveCoordinatesInPreferences((float)location.getLatitude(), (float)location.getLongitude());
addProximityAlert(location.getLatitude(), location.getLongitude());
}
private void addProximityAlert(double latitude, double longitude) {
Intent intent = new Intent(PROX_ALERT_INTENT);
PendingIntent proximityIntent = PendingIntent.getBroadcast(this, 0, intent, 0);
locationManager.addProximityAlert(
latitude, // the latitude of the central point of the alert region
longitude, // the longitude of the central point of the alert region
POINT_RADIUS, // the radius of the central point of the alert region, in meters
PROX_ALERT_EXPIRATION, // time for this proximity alert, in milliseconds, or -1 to indicate no expiration
proximityIntent // will be used to generate an Intent to fire when entry to or exit from the alert region is detected
);
IntentFilter filter = new IntentFilter(PROX_ALERT_INTENT);
registerReceiver(new ProximityIntentReceiver(), filter);
}
private void populateCoordinatesFromLastKnownLocation() {
Location location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location!=null) {
latitudeEditText.setText(nf.format(location.getLatitude()));
longitudeEditText.setText(nf.format(location.getLongitude()));
}
}
private void saveCoordinatesInPreferences(float latitude, float longitude) {
SharedPreferences prefs = this.getSharedPreferences(getClass().getSimpleName(), Context.MODE_PRIVATE);
SharedPreferences.Editor prefsEditor = prefs.edit();
prefsEditor.putFloat(POINT_LATITUDE_KEY, latitude);
prefsEditor.putFloat(POINT_LONGITUDE_KEY, longitude);
prefsEditor.commit();
}
private Location retrievelocationFromPreferences() {
SharedPreferences prefs = this.getSharedPreferences(getClass().getSimpleName(), Context.MODE_PRIVATE);
Location location = new Location("POINT_LOCATION");
location.setLatitude(prefs.getFloat(POINT_LATITUDE_KEY, 0));
location.setLongitude(prefs.getFloat(POINT_LONGITUDE_KEY, 0));
return location;
}
public class MyLocationListener implements LocationListener {
public void onLocationChanged(Location location) {
Location pointLocation = retrievelocationFromPreferences();
float distance = location.distanceTo(pointLocation);
Toast.makeText(ProxAlertActivity.this,
"Distance from Point:"+distance, Toast.LENGTH_LONG).show();
}
public void onStatusChanged(String s, int i, Bundle b) {
}
public void onProviderDisabled(String s) {
}
public void onProviderEnabled(String s) {
}
}
}
ProximityIntentReceiver.java
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.graphics.Color;
import android.location.LocationManager;
import android.util.Log;
public class ProximityIntentReceiver extends BroadcastReceiver {
private static final int NOTIFICATION_ID = 1000;
@Override
public void onReceive(Context context, Intent intent) {
String key = LocationManager.KEY_PROXIMITY_ENTERING;
Boolean entering = intent.getBooleanExtra(key, false);
if (entering) {
Log.d(getClass().getSimpleName(), "entering");
}
else {
Log.d(getClass().getSimpleName(), "exiting");
}
NotificationManager notificationManager =
(NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, null, 0);
Notification notification = createNotification();
notification.setLatestEventInfo(context,
"Proximity Alert!", "You are near your point of interest.", pendingIntent);
notificationManager.notify(NOTIFICATION_ID, notification);
}
private Notification createNotification() {
Notification notification = new Notification();
notification.icon = R.drawable.ic_menu_notifications;
notification.when = System.currentTimeMillis();
notification.flags |= Notification.FLAG_AUTO_CANCEL;
notification.flags |= Notification.FLAG_SHOW_LIGHTS;
notification.defaults |= Notification.DEFAULT_VIBRATE;
notification.defaults |= Notification.DEFAULT_LIGHTS;
notification.ledARGB = Color.WHITE;
notification.ledOnMS = 1500;
notification.ledOffMS = 1500;
return notification;
}
}