我想捕获Firebase中的数据的纬度和经度，并在Google地图中添加为书签。但是它在第136行给出错误＆gt;＆gt;
String latitude = dataSnapshotChild.child("latitude").GetValue().ToString();
查看logcat，我能够捕获纬度和经度并使用Log.v进行打印，并在应用程序崩溃后进行打印。我只有这个类和布局。我的代码出了什么问题？
我的Firebase结构如下所示：
Data
uploads
-KqQSusAUJs_MQs_giJr
latitude: -16.160159
longitude: -37.160730
-KqQquseUJs_MQs_gits
latitude: -14.692552
longitude: -37.399593
我的代码：
public class MainActivity extends FragmentActivity implements OnMapReadyCallback, LocationListener {
final static int PERMISSION_ALL = 1;
final static String[] PERMISSIONS = {android.Manifest.permission.ACCESS_COARSE_LOCATION,
Manifest.permission.ACCESS_FINE_LOCATION};
private GoogleMap mMap;
MarkerOptions mo;
Marker marker;
LocationManager locationManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FirebaseApp.initializeApp(this);
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
mo = new MarkerOptions().position(new LatLng(0, 0)).title("I am here!");
if (Build.VERSION.SDK_INT >= 23 && !isPermissionGranted()) {
requestPermissions(PERMISSIONS, PERMISSION_ALL);
} else requestLocation();
if (!isLocationEnabled())
showAlert(1);
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
marker = mMap.addMarker(mo);
ref.child("uploads").addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
Iterator<DataSnapshot> dataSnapshotsChat = dataSnapshot.getChildren().iterator();
while (dataSnapshotsChat.hasNext()) {
DataSnapshot dataSnapshotChild = dataSnapshotsChat.next();
String latitude = dataSnapshotChild.child("latitude").getValue().toString();
String longitude = dataSnapshotChild.child("longitude").getValue().toString();
double latitude1 = Double.parseDouble(latitude);
double longitude1 = Double.parseDouble(longitude);
LatLng local = new LatLng(latitude1, longitude1);
@Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
});
}
private LatLngBounds maplocal = new LatLngBounds(
new LatLng(-16.5191275, -49.7484793), new LatLng(-16.5191275, -49.7484793));
@Override
public void onLocationChanged(Location location) {
LatLng myCoordinates = new LatLng(location.getLatitude(), location.getLongitude());
marker.setPosition(myCoordinates);
mMap.moveCamera(CameraUpdateFactory.newLatLng(myCoordinates));
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(maplocal.getCenter(), 12));
}
@Override
public void onStatusChanged(String s, int i, Bundle bundle) {
}
@Override
public void onProviderEnabled(String s) {
}
@Override
public void onProviderDisabled(String s) {
}
private void requestLocation() {
Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_FINE);
criteria.setPowerRequirement(Criteria.POWER_HIGH);
String provider = locationManager.getBestProvider(criteria, true);
locationManager.requestLocationUpdates(provider, 10000, 10, this);
}
private boolean isLocationEnabled() {
return locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER) ||
locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
}
private boolean isPermissionGranted() {
if (checkSelfPermission(android.Manifest.permission.ACCESS_COARSE_LOCATION)
== PackageManager.PERMISSION_GRANTED || checkSelfPermission(android.Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
Log.v("mylog", "Permission is granted");
return true;
} else {
Log.v("mylog", "Permission not granted");
return false;
}
}
private void showAlert(final int status) {
String message, title, btnText;
if (status == 1) {
message = "Your Locations Settings is set to 'Off'.\nPlease Enable Location to " +
"use this app";
title = "Enable Location";
btnText = "Location Settings";
} else {
message = "Please allow this app to access location!";
title = "Permission access";
btnText = "Grant";
}
final AlertDialog.Builder dialog = new AlertDialog.Builder(this);
dialog.setCancelable(false);
dialog.setTitle(title)
.setMessage(message)
.setPositiveButton(btnText, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface paramDialogInterface, int paramInt) {
if (status == 1) {
Intent myIntent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(myIntent);
} else
requestPermissions(PERMISSIONS, PERMISSION_ALL);
}
})
.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface paramDialogInterface, int paramInt) {
finish();
}
});
dialog.show();
}
}
logcat的：
08-06 20:32:59.201 31120-31120/com.chico.testemarker V/log: lat/lng: (-16.160159,-37.160730)
08-06 20:32:59.201 31120-31120/com.chico.testemarker V/log: lat/lng: (-14.692552,-37.399593)
08-06 20:32:59.201 31120-31120/com.chico.testemarker D/AndroidRuntime: Shutting down VM
08-06 20:32:59.201 31120-31120/com.chico.testemarker E/UncaughtException: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at com.chico.testemarker.MainActivity$1.onDataChange(MainActivity.java:136)
at com.google.android.gms.internal.zzbpx.zza(Unknown Source)
at com.google.android.gms.internal.zzbqx.zzZS(Unknown Source)
at com.google.android.gms.internal.zzbra$1.run(Unknown Source)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7230)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
08-06 20:32:59.241 31120-31435/com.chico.testemarker I/DynamiteModule: Considering local module com.google.android.gms.tagmanager:9 and remote module com.google.android.gms.tagmanager:12
08-06 20:32:59.241 31120-31435/com.chico.testemarker I/DynamiteModule: Selected remote version of com.google.android.gms.tagmanager, version >= 12
08-06 20:32:59.251 31120-31509/com.chico.testemarker I/System.out: (HTTPLog)-Static: isSBSettingEnabled false
08-06 20:32:59.251 31120-31509/com.chico.testemarker I/System.out: (HTTPLog)-Static: isSBSettingEnabled false
08-06 20:32:59.251 31120-31512/com.chico.testemarker I/System.out: (HTTPLog)-Static: isSBSettingEnabled false
08-06 20:32:59.251 31120-31509/com.chico.testemarker I/qtaguid: Tagging socket 35 with tag 3000110100000000{805310721,0} uid -1, pid: 31120, getuid(): 10228
08-06 20:32:59.251 31120-31512/com.chico.testemarker I/System.out: (HTTPLog)-Static: isSBSettingEnabled false
08-06 20:32:59.251 31120-31511/com.chico.testemarker I/System.out: (HTTPLog)-Static: isSBSettingEnabled false
08-06 20:32:59.251 31120-31511/com.chico.testemarker I/System.out: (HTTPLog)-Static: isSBSettingEnabled false
08-06 20:32:59.251 31120-31511/com.chico.testemarker I/qtaguid: Tagging socket 97 with tag 3000110100000000{805310721,0} uid -1, pid: 31120, getuid(): 10228
08-06 20:32:59.251 31120-31512/com.chico.testemarker I/qtaguid: Tagging socket 83 with tag 3000110100000000{805310721,0} uid -1, pid: 31120, getuid(): 10228
08-06 20:32:59.261 31120-31510/com.chico.testemarker I/System.out: (HTTPLog)-Static: isSBSettingEnabled false
08-06 20:32:59.261 31120-31510/com.chico.testemarker I/System.out: (HTTPLog)-Static: isSBSettingEnabled false
08-06 20:32:59.261 31120-31510/com.chico.testemarker I/qtaguid: Tagging socket 98 with tag 3000110100000000{805310721,0} uid -1, pid: 31120, getuid(): 10228
08-06 20:32:59.421 31120-31435/com.chico.testemarker W/GoogleTagManager: No container asset found in /assets/containers. Checking top level /assets directory for container assets.
08-06 20:32:59.461 31120-31120/com.chico.testemarker E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.chico.testemarker, PID: 31120
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at com.chico.testemarker.MainActivity$1.onDataChange(MainActivity.java:136)
at com.google.android.gms.internal.zzbpx.zza(Unknown Source)
at com.google.android.gms.internal.zzbqx.zzZS(Unknown Source)
at com.google.android.gms.internal.zzbra$1.run(Unknown Source)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7230)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
08-06 20:32:59.471 31120-31435/com.chico.testemarker W/GoogleTagManager: Tag Manager's event handler WILL NOT be installed (no container loaded)
08-06 20:32:59.471 31120-31435/com.chico.testemarker I/GoogleTagManager: Tag Manager initilization took 206ms
08-06 20:32:59.481 31120-31824/com.chico.testemarker I/FirebaseCrash: Sending crashes
答案 0 :(得分：0)
尝试使用简单的东西，比如for循环而不是迭代器，我认为这就是导致你在null对象上调用toString（）的原因。
答案 1 :(得分：0)
已解决，我认为它与＆＃34; public void onLocationChanged＆＃34;相冲突。我刚刚删除了那部分代码。有效！！！
private LatLngBounds maplocal = new LatLngBounds(
new LatLng(-16.5191275, -49.7484793), new LatLng(-16.5191275, -49.7484793));
@Override
public void onLocationChanged(Location location) {
LatLng myCoordinates = new LatLng(location.getLatitude(), location.getLongitude());
marker.setPosition(myCoordinates);
mMap.moveCamera(CameraUpdateFactory.newLatLng(myCoordinates));
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(maplocal.getCenter(), 12));
}
@Override
public void onStatusChanged(String s, int i, Bundle bundle) {
}
@Override
public void onProviderEnabled(String s) {
}
@Override
public void onProviderDisabled(String s) {
}
private void requestLocation() {
Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_FINE);
criteria.setPowerRequirement(Criteria.POWER_HIGH);
String provider = locationManager.getBestProvider(criteria, true);
locationManager.requestLocationUpdates(provider, 10000, 10, this);
}
private boolean isLocationEnabled() {
return locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER) ||
locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
}
private boolean isPermissionGranted() {
if (checkSelfPermission(android.Manifest.permission.ACCESS_COARSE_LOCATION)
== PackageManager.PERMISSION_GRANTED || checkSelfPermission(android.Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
Log.v("mylog", "Permission is granted");
return true;
} else {
Log.v("mylog", "Permission not granted");
return false;
}
}
private void showAlert(final int status) {
String message, title, btnText;
if (status == 1) {
message = "Your Locations Settings is set to 'Off'.\nPlease Enable Location to " +
"use this app";
title = "Enable Location";
btnText = "Location Settings";
} else {
message = "Please allow this app to access location!";
title = "Permission access";
btnText = "Grant";
}
final AlertDialog.Builder dialog = new AlertDialog.Builder(this);
dialog.setCancelable(false);
dialog.setTitle(title)
.setMessage(message)
.setPositiveButton(btnText, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface paramDialogInterface, int paramInt) {
if (status == 1) {
Intent myIntent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(myIntent);
} else
requestPermissions(PERMISSIONS, PERMISSION_ALL);
}
})
.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface paramDialogInterface, int paramInt) {
finish();
}
});
dialog.show();
}