我有一个用gps计算距离和速度的应用程序 速度很快 但距离总是等于零!!
起初我没有将float [] dist初始化为零..但是一旦找到gps就崩溃了！
这就是代码
public class Main_Activity extends Activity {
TextView tvdistance;
TextView tvSpeed;
double currentLon = 0;
double currentLat = 0;
double lastLon = 0;
double lastLat = 0;
double distance = 0;
float[] dist = {
0, 0, 0
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_layout);
tvdistance = (TextView) findViewById(R.id.tvdistance);
tvSpeed = (TextView) findViewById(R.id.tvspeed1);
LocationManager lm = (LocationManager) getSystemService(LOCATION_SERVICE);
lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, Loclist);
Location loc2 = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (loc == null) {
tvdistance.setText("No GPS location found");
}
else {
// set Current latitude and longitude
currentLon = loc.getLongitude();
currentLat = loc.getLatitude();
}
// Set the last latitude and longitude
lastLat = currentLat;
lastLon = currentLon;
}
LocationListener Loclist = new LocationListener() {
@Override
public void onLocationChanged(Location location) {
// TODO Auto-generated method stub
// start location manager
LocationManager lm = (LocationManager) getSystemService(LOCATION_SERVICE);
// Get last location
Location loc = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
// Request new location
lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, Loclist);
// Get new location
Location loc2 = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
// get the current lat and long
currentLat = loc.getLatitude();
currentLon = loc.getLongitude();
if (currentLat != 0 && currentLon != 0) {
Location.distanceBetween(currentLat, currentLon, location.getLatitude(),
location.getLongitude(), dist);
distance += (long) dist[0];
}
currentLat = location.getLatitude();
currentLon = location.getLongitude();
float speed = location.getSpeed();
tvSpeed.setText("Speed = " + speed / 1000 * 60 * 60 + "Km/h");
tvdistance.setText("Distance = " + distance);
}
@Override
public void onProviderDisabled(String provider) {
// TODO Auto-generated method stub
}
@Override
public void onProviderEnabled(String provider) {
// TODO Auto-generated method stub
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
// TODO Auto-generated method stub
}
};
}
答案 0 :(得分：0)
由于您刚刚获得了位置修复，我完全希望从getLastKnownLocation返回的位置与您在location中获得的位置相同。这意味着两者之间的距离正确0。如果您想要旧位置，则需要自己存储。
答案 1 :(得分：-1)
以下是从GPS提供商处获取位置更新的完整代码
public class MainActivity extends Activity {
private GoogleMap googleMap;
// The minimum distance to change Updates in meters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 1; // 1
// meters
// The minimum time between updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 1000; // 1
// second
// Declaring a Location Manager
protected LocationManager locationManager;
// The alert dialog to enable GPS
private Dialog alertDialog;
// flag for GPS status
boolean isGPSEnabled = false;
Location location; // location
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
/*
* (non-Javadoc)
*
* @see android.app.Activity#onStart()
*/
@Override
protected void onStart() {
// fetching your current location
super.onStart();
googleMap = ((MapFragment) getFragmentManager().findFragmentById(
R.id.map)).getMap();
if (googleMap != null) {
googleMap.setMyLocationEnabled(true);
googleMap.getUiSettings().setZoomControlsEnabled(true);
googleMap.getUiSettings().setMyLocationButtonEnabled(true);
googleMap.getUiSettings().setAllGesturesEnabled(true);
}
// Getting current location and adding the marker
locateMe();
}
/**
*
*/
private void locateMe() {
// Checking for GPS Enabled
locationManager = (LocationManager) this
.getSystemService(Context.LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
if (!isGPSEnabled) {
// GPS is disabled
askUserToEnableGPS();
}
}
/**
*
*/
private void askUserToEnableGPS() {
// Asking user to enable GPS
// 1. Instantiate an AlertDialog.Builder with its constructor
AlertDialog.Builder builder = new AlertDialog.Builder(this);
// 2. Chain together various setter methods to set the dialog
// characteristics
builder.setMessage(R.string.generic_gps_not_found)
.setTitle(R.string.generic_gps_not_found_message_title)
.setPositiveButton(R.string.generic_yes,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int id) {
// User selected yes
Intent intent = new Intent(
Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(intent);
}
})
.setNegativeButton(R.string.generic_no,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int id) {
// User selected no
}
});
// 3. Get the AlertDialog from create()
AlertDialog dialog = builder.create();
dialog.show();
}
/*
* (non-Javadoc)
*
* @see android.app.Activity#onResume()
*/
@Override
protected void onResume() {
// Getting location from GPS
super.onResume();
// getting GPS status
isGPSEnabled = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
if (isGPSEnabled) {
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER, MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, listener);
Log.e("GPS Enabled", "GPS Enabled");
location = locationManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
}
}
LocationListener listener = new LocationListener() {
@Override
public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
// TODO Auto-generated method stub
}
@Override
public void onProviderEnabled(String arg0) {
// TODO Auto-generated method stub
}
@Override
public void onProviderDisabled(String arg0) {
// TODO Auto-generated method stub
}
@Override
public void onLocationChanged(Location arg0) {
// Setting the marker
if (googleMap == null || location == null) {
return;
} else {
googleMap.moveCamera(CameraUpdateFactory.newLatLng(new LatLng(
location.getLatitude(), location.getLongitude())));
final Handler handler1 = new Handler();
handler1.postDelayed(new Runnable() {
@Override
public void run() {
// Do something after 3000ms
googleMap.animateCamera(CameraUpdateFactory.zoomTo(17));
}
}, 1000);
Marker myLocation = googleMap.addMarker(new MarkerOptions()
.position(
new LatLng(location.getLatitude(), location
.getLongitude()))
.title("Me")
.snippet("I am here")
.icon(BitmapDescriptorFactory
.fromResource(R.drawable.ic_launcher)));
}
locationManager.removeUpdates(listener);
locationManager = null;
}
};
}
现在您可以使用各种方法来存储您的位置。以下是一些方法：
您可以参考this链接。