我正在尝试使用Geofire来存储和显示在地图上登录的用户我是android studio中的新用户 我收到这个错误 java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.parthtiwari.trace / com.example.parthtiwari.trace.tracking}：java.lang.NullPointerException：尝试调用虚拟方法'com.google.android.gms空对象引用上的.maps.model.Circle com.google.android.gms.maps.GoogleMap.addCircle（com.google.android.gms.maps.model.CircleOptions）'
import android.app.AlertDialog;
import android.graphics.Color;
import android.os.Bundle;
import android.os.Handler;
import android.os.SystemClock;
import android.support.v4.app.FragmentActivity;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.view.animation.Interpolator;
import com.firebase.geofire.GeoFire;
import com.firebase.geofire.GeoLocation;
import com.firebase.geofire.GeoQuery;
import com.firebase.geofire.GeoQueryEventListener;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.*;
import com.google.firebase.FirebaseApp;
import com.google.firebase.FirebaseOptions;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.FirebaseDatabase;
import java.util.HashMap;
import java.util.Map;
public class tracking extends FragmentActivity implements
GeoQueryEventListener,OnMapReadyCallback,
GoogleMap.OnCameraChangeListener{
private static final GeoLocation INITIAL_CENTER = new GeoLocation(22.7789,
-78.4017);
private static final int INITIAL_ZOOM_LEVEL = 14;
private static final String GEO_FIRE_DB = "https://trace-
5fa8c.firebaseio.com";
private static final String GEO_FIRE_REF = GEO_FIRE_DB + "/_geofire";
private GoogleMap mMap;
private GoogleMap map;
private Circle searchCircle;
private GeoFire geoFire;
private GeoQuery geoQuery;
private Map<String,Marker> markers;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_tracking);
// Obtain the SupportMapFragment and get notified when the map is ready
to be used.
SupportMapFragment mapFragment = (SupportMapFragment)
getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync((OnMapReadyCallback) this);
LatLng latLngCenter = new LatLng(INITIAL_CENTER.latitude,
INITIAL_CENTER.longitude);
this.searchCircle = this.map.addCircle(new
CircleOptions().center(latLngCenter).radius(1000));
this.searchCircle.setFillColor(Color.argb(66, 255, 0, 255));
this.searchCircle.setStrokeColor(Color.argb(66, 0, 0, 0));
this.map.moveCamera(CameraUpdateFactory.newLatLngZoom(latLngCenter,
INITIAL_ZOOM_LEVEL));
this.map.setOnCameraChangeListener(this);
FirebaseOptions options = new FirebaseOptions.Builder().setApplicationId("geofire").setDatabaseUrl(GEO_FIRE_DB).build();
FirebaseApp app = FirebaseApp.initializeApp(this, options);
// setup GeoFire
this.geoFire = new GeoFire(FirebaseDatabase.getInstance(app).getReferenceFromUrl(GEO_FIRE_REF));
// radius in km
this.geoQuery = this.geoFire.queryAtLocation(INITIAL_CENTER, 1);
// setup markers
this.markers = new HashMap<String, Marker>();
}
@Override
protected void onStop() {
super.onStop();
// remove all event listeners to stop updating in the background
this.geoQuery.removeAllListeners();
for (Marker marker: this.markers.values()) {
marker.remove();
}
this.markers.clear();
}
@Override
protected void onStart() {
super.onStart();
// add an event listener to start updating locations again
this.geoQuery.addGeoQueryEventListener(this);
}
@Override
public void onKeyEntered(String key, GeoLocation location) {
// Add a new marker to the map
Marker marker = this.map.addMarker(new MarkerOptions().position(new
LatLng(location.latitude, location.longitude)));
this.markers.put(key, marker);
}
@Override
public void onKeyExited(String key) {
// Remove any old marker
Marker marker = this.markers.get(key);
if (marker != null) {
marker.remove();
this.markers.remove(key);
}
}
@Override
public void onKeyMoved(String key, GeoLocation location) {
// Move the marker
Marker marker = this.markers.get(key);
if (marker != null) {
this.animateMarkerTo(marker, location.latitude, location.longitude);
}
}
@Override
public void onGeoQueryReady() {
}
@Override
public void onGeoQueryError(DatabaseError error) {
new AlertDialog.Builder(this)
.setTitle("Error")
.setMessage("There was an unexpected error querying GeoFire: " +
error.getMessage())
.setPositiveButton(android.R.string.ok, null)
.setIcon(android.R.drawable.ic_dialog_alert)
.show();
}
// Animation handler for old APIs without animation support
private void animateMarkerTo(final Marker marker, final double lat, final
double lng) {
final Handler handler = new Handler();
final long start = SystemClock.uptimeMillis();
final long DURATION_MS = 3000;
final Interpolator interpolator = new
AccelerateDecelerateInterpolator();
final LatLng startPosition = marker.getPosition();
handler.post(new Runnable() {
@Override
public void run() {
float elapsed = SystemClock.uptimeMillis() - start;
float t = elapsed/DURATION_MS;
float v = interpolator.getInterpolation(t);
double currentLat = (lat - startPosition.latitude) * v +
startPosition.latitude;
double currentLng = (lng - startPosition.longitude) * v +
startPosition.longitude;
marker.setPosition(new LatLng(currentLat, currentLng));
// if animation is not finished yet, repeat
if (t < 1) {
handler.postDelayed(this, 16);
}
}
});
}
private double zoomLevelToRadius(double zoomLevel) {
// Approximation to fit circle into view
return 16384000/Math.pow(2, zoomLevel);
}
@Override
public void onCameraChange(CameraPosition cameraPosition) {
LatLng center = cameraPosition.target;
double radius = zoomLevelToRadius(cameraPosition.zoom);
this.searchCircle.setCenter(center);
this.searchCircle.setRadius(radius);
this.geoQuery.setCenter(new GeoLocation(center.latitude,
center.longitude));
// radius in km
this.geoQuery.setRadius(radius/1000);
}
@Override
public void onMapReady(GoogleMap googleMap) {
}
}
答案 0 :(得分：0)
您正在使用此声明异步请求GoogleMap实例：
ng-options当地图可供使用时，将在此回调中向您报告：
mapFragment.getMapAsync((OnMapReadyCallback) this);
您需要从活动的@Override
public void onMapReady(GoogleMap googleMap) {
}
方法中获取使用地图的所有初始化代码，并将其移至onCreate()或从onMapReady()调用的方法。例如：
onMapReady()不清楚为什么要创建另一个应用实例。我不认为Geofire需要它。尝试使用默认值：
@Override
public void onMapReady(GoogleMap googleMap) {
map = googleMap;
//mMap = googleMap; // not used?
// all the map init stuff
LatLng latLngCenter = new LatLng(INITIAL_CENTER.latitude,
INITIAL_CENTER.longitude);
this.searchCircle = this.map.addCircle(new
CircleOptions().center(latLngCenter).radius(1000));
this.searchCircle.setFillColor(Color.argb(66, 255, 0, 255));
this.searchCircle.setStrokeColor(Color.argb(66, 0, 0, 0));
this.map.moveCamera(CameraUpdateFactory.newLatLngZoom(latLngCenter,
INITIAL_ZOOM_LEVEL));
this.map.setOnCameraChangeListener(this);
}