我需要将我当前的地理位置（纬度和经度）与我存储在数据库中的地理位置进行比较，如果两者之间的距离小于 2 公里，那么我想开始一些活动..但它不起作用..我是认为我的服务类中存在一些问题，因为我在后台服务中执行所有这些操作，该服务在我开始活动时开始......请告诉我做错了什么这是我的代码
package com.example.alert;
import java.util.ArrayList;
import java.util.List;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.IBinder;
import android.widget.Toast;
public class service extends Service{
LocationManager lm;
DatabaseHelper db=new DatabaseHelper(this);
List<Double> arlist=new ArrayList<Double>();
List<Double> arrylist=new ArrayList<Double>();
@Override
public IBinder onBind(Intent arg0) {
// TODO Auto-generated method stub
return null;
}
public void onCreate() {
LocationManager lm=(LocationManager)getSystemService(Context.LOCATION_SERVICE);
LocationListener ll=new MyLocationListener();
//lm.requestLocationUpdates( LocationManager.GPS_PROVIDER, 5*60*10000, 0, ll);
lm.requestLocationUpdates( LocationManager.GPS_PROVIDER, 0, 0, ll);
// Toast.makeText(this, "Background Service Created", Toast.LENGTH_LONG).show();
}
public void onDestroy() {
Toast.makeText(this, "My Service Stopped", Toast.LENGTH_LONG).show();
}
public void onStart(Intent intent, int startid) {
Toast.makeText(this, "Finding your Current Location.....", Toast.LENGTH_LONG).show();
// Intent myIntent=new Intent(service.this,CurrentLocation.class);
}
/* Class My Location Listener */
public class MyLocationListener implements LocationListener
{
public void onLocationChanged(Location loc)
{
if(loc!=null)
{
String Text = "My current location is: " +"Latitud = " + loc.getLatitude() +"Longitud = " + loc.getLongitude();
SQLiteDatabase y = db.getWritableDatabase();
Toast.makeText( getApplicationContext(),Text,Toast.LENGTH_SHORT).show();
// String t=loc.getLatitude().toString();
Cursor cr=null;
Cursor cur=null;
cur=y.rawQuery("SELECT longitude FROM"+ "data",null);
cur.moveToFirst();
cr=y.rawQuery("SELECT latitude FROM"+ "data",null);
cr.moveToFirst();
while(!cr.isAfterLast()) {
arlist.add(cr.getDouble(cr.getColumnIndex("latitude")));
cr.moveToNext();
}
while(!cur.isAfterLast()) {
arrylist.add(cr.getDouble(cr.getColumnIndex("ongitude")));
cur.moveToNext();
}
for(int i=0;i<arlist.size();i++){
if(calcDistance(loc.getLatitude(),loc.getLongitude(),arlist.get(i),arrylist.get(i))<5){
Intent myIntent=new Intent(service.this,SilVib.class);
startActivity(myIntent);
}
}
/* cr.moveToFirst();
while(!cr.isAfterLast()) {
al.add(cr.getString(cr.getColumnIndex(dbAdapter.KEY_NAME))); //add the item
cr.moveToNext();
}*/
// lm.addProximityAlert(loc.getLatitude(), loc.getLongitude(), 10009,, intent)
//for loop, alerters retrieving one by one
// x= calcDistance(loc.getLatitude(),loc.getLongitude(),z,y);
// if(x<1){
// Intent myIntent = new Intent(ViewAlerters.this,CallMode.class);
// startActivity(myIntent);
}
}
public void onProviderDisabled(String provider) {
// TODO Auto-generated method stub
Toast.makeText( getApplicationContext(),"Gps Disabled - @From :Alert Me",Toast.LENGTH_SHORT ).show();
}
public void onProviderEnabled(String provider) {
// TODO Auto-generated method stub
Toast.makeText( getApplicationContext(),"Gps Enabled - @From :Alert Me",Toast.LENGTH_SHORT).show();
}
public void onStatusChanged(String provider, int status, Bundle extras) {
// TODO Auto-generated method stub
}
}
public double calcDistance(double latA, double longA, double latB, double longB) {
double theDistance = (Math.sin(Math.toRadians(latA)) * Math.sin(Math.toRadians(latB)) + Math.cos(Math.toRadians(latA)) * Math.cos(Math.toRadians(latB)) * Math.cos(Math.toRadians(longA - longB)));
return new Double((Math.toDegrees(Math.acos(theDistance))) * 69.09*1.6093);
}
}
这是我更新的代码...每当我尝试使用意图启动此服务时，它都会强制关闭
package com.example.alert;
import java.util.ArrayList;
import java.util.List;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.IBinder;
import android.widget.Toast;
public class service extends Service{
LocationManager lm;
DatabaseHelper db=new DatabaseHelper(this);
List<Double> arlist=new ArrayList<Double>();
List<Double> arrylist=new ArrayList<Double>();
SQLiteDatabase y = db.getWritableDatabase();
@Override
public IBinder onBind(Intent arg0) {
// TODO Auto-generated method stub
return null;
}
public void onCreate() {
LocationManager lm=(LocationManager)getSystemService(Context.LOCATION_SERVICE);
LocationListener ll=new MyLocationListener();
//lm.requestLocationUpdates( LocationManager.GPS_PROVIDER, 5*60*10000, 0, ll);
lm.requestLocationUpdates( LocationManager.GPS_PROVIDER, 0, 0, ll);
}
public void onDestroy() {
Toast.makeText(this, "My Service Stopped", Toast.LENGTH_LONG).show();
}
public void onStart(Intent intent, int startid) {
Toast.makeText(this, "Finding your Current Location.....", Toast.LENGTH_LONG).show();
// Intent myIntent=new Intent(service.this,CurrentLocation.class);
}
/* Class My Location Listener */
public class MyLocationListener implements LocationListener
{
public void onLocationChanged(Location loc)
{
if(loc!=null)
{
String Text = "My current location is: " +"Latitud = " + loc.getLatitude() +"Longitud = " + loc.getLongitude();
Toast.makeText( getApplicationContext(),Text,Toast.LENGTH_SHORT).show();
// String t=loc.getLatitude().toString();
Cursor cr=null;
Cursor cur=null;
cur=y.rawQuery("SELECT longitude FROM"+ "data",null);
cur.moveToFirst();
cr=y.rawQuery("SELECT latitude FROM"+ "data",null);
cr.moveToFirst();
while(!cr.isAfterLast()) {
arlist.add(cr.getDouble(cr.getColumnIndex("latitude")));
cr.moveToNext();
}
while(!cur.isAfterLast()) {
arrylist.add(cr.getDouble(cr.getColumnIndex("ongitude")));
cur.moveToNext();
}
for(int i=0;i<arlist.size();i++){
Location locB = new Location("point B");
locB.setLatitude(arlist.get(i));
locB.setLongitude(arrylist.get(i));
float distance=loc.distanceTo(locB);
if(distance<5){
Intent myIntent=new Intent(service.this,Notifier.class);
startActivity(myIntent);
}
}
}
}
public void onProviderDisabled(String provider) {
// TODO Auto-generated method stub
Toast.makeText( getApplicationContext(),"Gps Disabled - @From :Alert Me",Toast.LENGTH_SHORT ).show();
}
public void onProviderEnabled(String provider) {
// TODO Auto-generated method stub
Toast.makeText( getApplicationContext(),"Gps Enabled - @From :Alert Me",Toast.LENGTH_SHORT).show();
}
public void onStatusChanged(String provider, int status, Bundle extras) {
// TODO Auto-generated method stub
}
}
}
当我尝试使用 Intent 访问该服务时，这是我的 logcat
11-11 08:22:25.867: E/AndroidRuntime(813): FATAL EXCEPTION: main
11-11 08:22:25.867: E/AndroidRuntime(813): java.lang.RuntimeException: Unable to instantiate service com.example.alert.service: java.lang.NullPointerException
11-11 08:22:25.867: E/AndroidRuntime(813): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2347)
11-11 08:22:25.867: E/AndroidRuntime(813): at android.app.ActivityThread.access$1600(ActivityThread.java:130)
11-11 08:22:25.867: E/AndroidRuntime(813): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1277)
11-11 08:22:25.867: E/AndroidRuntime(813): at android.os.Handler.dispatchMessage(Handler.java:99)
11-11 08:22:25.867: E/AndroidRuntime(813): at android.os.Looper.loop(Looper.java:137)
11-11 08:22:25.867: E/AndroidRuntime(813): at android.app.ActivityThread.main(ActivityThread.java:4745)
11-11 08:22:25.867: E/AndroidRuntime(813): at java.lang.reflect.Method.invokeNative(Native Method)
11-11 08:22:25.867: E/AndroidRuntime(813): at java.lang.reflect.Method.invoke(Method.java:511)
11-11 08:22:25.867: E/AndroidRuntime(813): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
11-11 08:22:25.867: E/AndroidRuntime(813): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-11 08:22:25.867: E/AndroidRuntime(813): at dalvik.system.NativeStart.main(Native Method)
11-11 08:22:25.867: E/AndroidRuntime(813): Caused by: java.lang.NullPointerException
11-11 08:22:25.867: E/AndroidRuntime(813): at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:221)
11-11 08:22:25.867: E/AndroidRuntime(813): at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
11-11 08:22:25.867: E/AndroidRuntime(813): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
11-11 08:22:25.867: E/AndroidRuntime(813): at com.example.alert.service.<init>(service.java:25)
11-11 08:22:25.867: E/AndroidRuntime(813): at java.lang.Class.newInstanceImpl(Native Method)
11-11 08:22:25.867: E/AndroidRuntime(813): at java.lang.Class.newInstance(Class.java:1319)
11-11 08:22:25.867: E/AndroidRuntime(813): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2344)