不从线程接收位置数据

Question

我正在尝试使用计时器每隔一段时间发送包含用户位置的文本消息。最初，我遇到了一个空指针异常，这是我犯的一个简单错误。一旦解决这个问题，一切似乎都运行良好。但是，它永远不会得到我的位置，因此，不断发送的文本说"无法接收位置"。

我要问的是为什么它没有得到我的位置？我该怎么做才能解决问题？

没有logcat错误，我正在使用两个模拟器来测试这个应用程序(从一个发送到另一个)。如果您能提供任何帮助或解决方案，我们将不胜感激！如果我忽略了一些看似非常简单的事情，请提醒我我正在这样做。谢谢！

代码如下：

public class MessageService extends Service{
int counter = 0;
private Timer timer = new Timer();
public String textTime, phoneNumber;
public int updateInterval;
int lat, lng;
String coordinates, latitude, longitude;
LocationManager locationManager;
@Override
public IBinder onBind(Intent arg0) {
return null;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId){
//receives the intent extras from the calling intent
textTime = intent.getStringExtra("textTime");
phoneNumber = intent.getStringExtra("phone");
phoneNumber = "5556";
//the following if statement has to do with transferring the string textTime into a number that can be used
if (textTime.equals("15 Minutes")) {
updateInterval = (15 * (60000));
}else if (textTime.equals("30 Minutes")) {
updateInterval = (30 * (60000));
}else if (textTime.equals("1 Hour")){
updateInterval = (60 * (60000));
}else {
updateInterval = (15 * (60000));
}
locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
new Thread(){
public void run(){
Looper.prepare();
// Define a listener that responds to location updates
LocationListener locationListener = new LocationListener() {
public void onLocationChanged(Location location) {
// Called when a new location is found by the network location provider.
//makeUseOfNewLocation(location);
lat = (int) (location.getLatitude() * 1E6);
lng = (int) (location.getLongitude() * 1E6);
latitude = Integer.toString(lat);
longitude = Integer.toString(lng);
coordinates = "Coordinates: " + latitude + ", " + longitude + ". Latitude: " + latitude + " Longitude: " + longitude + ". Respond 'END' to stop texts."; 
}
public void onStatusChanged(String provider, int status, Bundle extras) {}
public void onProviderEnabled(String provider) {}
public void onProviderDisabled(String provider) {}
};
Looper.loop();
if (locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)){
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
}else{
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener);
}
}
}.start();

//the following method should use a timer to send a sms message in a timed interval. It also should implement using a different thread
doSomethingRepeatedly();
return START_STICKY;
}
public void doSomethingRepeatedly(){
timer.scheduleAtFixedRate(new TimerTask() {
public void run() {
//the following code should be what is done repeatedly
//Log.d("MessageService", String.valueOf(++counter));
sendSmsMessage();
}
}, 0, updateInterval);
}
//the following code handles sending the text message
public void sendSmsMessage(){
SmsManager sms = SmsManager.getDefault();
if (coordinates == null || coordinates.equals("")){
coordinates = "Could Not Receive Location";
}
sms.sendTextMessage(phoneNumber, null, coordinates , null, null);
}
public void onDestroy() {
super.onDestroy();
if (timer != null) {
timer.cancel();
}
}


}//end of service

Answer 1

您的位置侦听器可能在调用onLocationChanged()之前就被销毁了。您的服务应实现 LocationListener 本身。

---

public class MessageService extends Service implements LocationListener {
int counter = 0;
private Timer timer = new Timer();
public String textTime, phoneNumber;
public int updateInterval;
int lat, lng;
String coordinates, latitude, longitude;
LocationManager locationManager;
@Override
public IBinder onBind(Intent arg0) {
return null;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId){
//receives the intent extras from the calling intent
textTime = intent.getStringExtra("textTime");
phoneNumber = intent.getStringExtra("phone");
phoneNumber = "5556";
//the following if statement has to do with transferring the string textTime into a number that can be used
if (textTime.equals("15 Minutes")) {
updateInterval = (15 * (60000));
}else if (textTime.equals("30 Minutes")) {
updateInterval = (30 * (60000));
}else if (textTime.equals("1 Hour")){
updateInterval = (60 * (60000));
}else {
updateInterval = (15 * (60000));
}
locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
if (locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)){
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
}else{
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, this);
}
//the following method should use a timer to send a sms message in a timed interval. It also should implement using a different thread
doSomethingRepeatedly();
return START_STICKY;
}
public void doSomethingRepeatedly(){
timer.scheduleAtFixedRate(new TimerTask() {
public void run() {
//the following code should be what is done repeatedly
//Log.d("MessageService", String.valueOf(++counter));
sendSmsMessage();
}
}, 0, updateInterval);
}
//the following code handles sending the text message
public void sendSmsMessage(){
SmsManager sms = SmsManager.getDefault();
if (coordinates == null || coordinates.equals("")){
coordinates = "Could Not Receive Location";
}
sms.sendTextMessage(phoneNumber, null, coordinates , null, null);
}
public void onDestroy() {
super.onDestroy();
if (timer != null) {
timer.cancel();
}
}
@Override
public void onLocationChanged(Location location) {
// Called when a new location is found by the network location provider.
//makeUseOfNewLocation(location);
lat = (int) (location.getLatitude() * 1E6);
lng = (int) (location.getLongitude() * 1E6);
latitude = Integer.toString(lat);
longitude = Integer.toString(lng);
coordinates = "Coordinates: " + latitude + ", " + longitude + ". Latitude: " + latitude + " Longitude: " + longitude + ". Respond 'END' to stop texts."; 
}
@Override
public void onProviderDisabled(String provider) {}
@Override
public void onProviderEnabled(String provider) {}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {}
}

Answer 2

我不太理解您的代码，但是如果您希望一个线程更新coordinates字段，然后另一个线程读取coordinates的内容，则需要使coordinates字段volatile。

线程之间共享的任何值都需要同步或以某种方式跨越内存屏障才能可见。