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nullpointerexception，这是由于我犯了一个简单的错误。一旦修复，一切似乎都运行良好。但是，它永远不会获取我的位置，因此，持续发送的文本说“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，我使用两个模拟器来测试这个应用程序（从一个发送文本到另一个）。如果您能提供任何帮助或解决方案，我们将不胜感激！如果我忽略了一些似乎非常简单的事情，请提醒我，我正在这样做。谢谢！
以下是代码：
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
答案 0 :(得分：3)
您的LocationListener可能在被调用onLocationChanged()之前被销毁。您的服务应该实现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) {}
}
答案 1 :(得分：1)
我无法理解你的代码，但是如果你期望一个线程更新coordinates字段然后另一个线程来读取coordinates的内容，你需要制作{{ 1}}字段coordinates。
线程之间共享的任何值都需要同步或以某种方式跨越memory barrier才能显示。