I am trying to pull the Location at regular intervals and send it over the network. Before doing that I feel it's important to verify that I am pulling the location correctly! To do that I attempt to pull the location and send a Message to a Handler which displays it on the screen. I searched all over and in fact used a very useful code segment on stack overflow (Thank you very much!) What is the simplest and most robust way to get the user's current location on Android?
Heres some code:
MyLocation (From the example):
package com.Locator;
import java.util.Timer;
import java.util.TimerTask;
import android.content.Context;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
public class MyLocation {
Timer timer1;
LocationManager lm;
LocationResult locationResult;
boolean gps_enabled=false;
boolean network_enabled=false;
public boolean getLocation(Context context, LocationResult result)
{
//I use LocationResult callback class to pass location value from MyLocation to user code.
locationResult=result;
if(lm==null)
lm = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
//exceptions will be thrown if provider is not permitted.
try{gps_enabled=lm.isProviderEnabled(LocationManager.GPS_PROVIDER);}catch(Exception ex){}
try{network_enabled=lm.isProviderEnabled(LocationManager.NETWORK_PROVIDER);}catch(Exception ex){}
//don't start listeners if no provider is enabled
if(!gps_enabled && !network_enabled)
return false;
if(gps_enabled)
lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListenerGps);
if(network_enabled)
lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListenerNetwork);
timer1=new Timer();
timer1.schedule(new GetLastLocation(), 20000);
return true;
}
LocationListener locationListenerGps = new LocationListener() {
public void onLocationChanged(Location location) {
timer1.cancel();
locationResult.gotLocation(location);
lm.removeUpdates(this);
lm.removeUpdates(locationListenerNetwork);
}
public void onProviderDisabled(String provider) {}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status, Bundle extras) {}
};
LocationListener locationListenerNetwork = new LocationListener() {
public void onLocationChanged(Location location) {
timer1.cancel();
locationResult.gotLocation(location);
lm.removeUpdates(this);
lm.removeUpdates(locationListenerGps);
}
public void onProviderDisabled(String provider) {}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status, Bundle extras) {}
};
class GetLastLocation extends TimerTask {
@Override
public void run() {
lm.removeUpdates(locationListenerGps);
lm.removeUpdates(locationListenerNetwork);
Location net_loc=null, gps_loc=null;
if(gps_enabled)
gps_loc=lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if(network_enabled)
net_loc=lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
//if there are both values use the latest one
if(gps_loc!=null && net_loc!=null){
if(gps_loc.getTime()>net_loc.getTime())
locationResult.gotLocation(gps_loc);
else
locationResult.gotLocation(net_loc);
return;
}
if(gps_loc!=null){
locationResult.gotLocation(gps_loc);
return;
}
if(net_loc!=null){
locationResult.gotLocation(net_loc);
return;
}
locationResult.gotLocation(null);
}
}
public static abstract class LocationResult{
public abstract void gotLocation(Location location);
}
}
Now when I use it like this it works fine (the following is code in the Main activity class):
MyLocation myLocation = new MyLocation();
LocationResult locationResult = new LocationResult(){
@Override
public void gotLocation(final Location location){
Message m = new Message();
m.obj = location.getLongitude() + " " + location.getLattitude();
threadHandler.sendMessage(m);
}
};
However I want to do this in regular intervals so I have something like this (The following code is in the main activity class, this time implementing Runnable):
....
new Thread(this).start();
....
public void run() {
MyLocation myLocation = new MyLocation();
LocationResult locationResult = new LocationResult(){
@Override
public void gotLocation(final Location location){
Message m = new Message();
m.obj = "SDFSDF";
threadHandler.sendMessage(m);
}
};
while(true) {
myLocation.getLocation(this, locationResult);
try {
Thread.sleep(30000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
NOTE: threadHandler is of type MyHandler as defined by:
class MyHandler extends Handler{
private TextView threadModifiedText;
public MyHandler(TextView tv) {
threadModifiedText = tv;
}
public void handleMessage(Message msg) {
// whenever the Thread notifies this handler we have
// only this behavior
threadModifiedText.setText((CharSequence)msg.obj);
}
}
I am getting errors about writing to a Handler from a thread that has not called Looper.prepare(). I have tried adding Looper.prepare() and Looper.loop() in various parts of my activity and thread to no avail. I have tried using a timer instead of a run() + sleep().
Later on instead of writing to a thread handler I am going to insert the location into a queue. Another thread which handles socket connections will check the emptiness of the queue. If it has an element it will dequeue() and send it away.
Please give me some advice.
