LocationManager.GPS_PROVIDERは0.0を返します

私のコードの問題は何ですか。gpsで現在地を取得したいのですが、毎回latとlngが0.0です。

locationManager=(LocationManager)this.getSystemService(Context.LOCATION_SERVICE);
locationListener=new LocationListener() {

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub

    }
    @Override
    public void onProviderEnabled(String provider) {
        // TODO Auto-generated method stub

    }
    @Override
    public void onProviderDisabled(String provider) {
        // TODO Auto-generated method stub

    }
    @Override
    public void onLocationChanged(Location location) {
        latitude=location.getLatitude();
        longitude=location.getLongitude();

        CurrentPostion();
        Toast.makeText(getApplicationContext(), latitude+"<(Lat,Lng)>"+longitude, Toast.LENGTH_SHORT).show();
    }
};
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 15000, 0, locationListener);

メソッドCurrentPostionは、現在の位置の地図上にアイコンを描画します。

public void CurrentPostion(){
    if(latitude!=0.0 && longitude!=0.0){
    MarkerOptions options=new MarkerOptions();
    options.position(new LatLng(latitude, longitude));
    options.icon(BitmapDescriptorFactory.fromResource(R.drawable.myicon));
    googleMap.addMarker(options);
    CameraPosition cameraPosition = new CameraPosition.Builder().target(new LatLng(latitude,longitude)).zoom(17).build();        
    googleMap.animateCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));
    }
}

私はすべての権限を持っています：

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<!-- Required to show current location -->
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

結果：

0.0 <（Lat、Lng）> 0.0