如何从firebase数据库添加谷歌地图标记

本文介绍了如何从firebase数据库添加谷歌地图标记的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 我想从Firebase数据库检索位置标记，但运行此代码后看不到任何标记。我试图制作 EventListener ，但是地图运行时没有任何标记。这是我的代码： $ p $ public class MapsActivity扩展FragmentActivity实现OnMapReadyCallback { 私有GoogleMap mMap; @Override protected void onCreate（Bundle savedInstanceState）{ super.onCreate（savedInstanceState）; setContentView（R.layout.activity_maps）; //获取SupportMapFragment并在地图准备好使用时得到通知。 SupportMapFragment mapFragment =（SupportMapFragment）getSupportFragmentManager（） .findFragmentById（R.id.map）; mapFragment.getMapAsync（this）; } / ** *操作一次可用的地图。 *当地图准备好被使用时，这个回调被触发。 *这是我们可以添加标记或线条，添加听众或移动相机的地方。在这种情况下， *我们只在澳大利亚悉尼附近添加一个标记。 *如果设备上没有安装Google Play服务，系统会提示用户在SupportMapFragment中安装 * it。只有当用户安装了 * Google Play服务并返回到应用后，此方法才会被触发。 * / @Override public void onMapReady（GoogleMap googleMap）{ mMap = googleMap; DatabaseReference ref = FirebaseDatabase.getInstance（）。getReference（）; 字符串rightLocation = ref.child（location_right）。toString（）; 字符串leftLocation = ref.child（location_left）。toString（）; double location_left = Double.valueOf（leftLocation）; double location_right = Double.valueOf（rightLocation）; LatLng sydney = new LatLng（location_left，location_right）; mMap.addMarker（new MarkerOptions（）。position（sydney）.title（Marker in Sydney））; mMap.moveCamera（CameraUpdateFactory.newLatLngZoom（sydney，18））; // b在悉尼添加一个标记并移动相机 $ b code $ b 解决方案您需要使用 ValueEventListener 从Firebase数据库获取数据。这在文档中进行了解释。 @Override public void onMapReady（GoogleMap googleMap）{ mMap = googleMap; DatabaseReference ref = FirebaseDatabase.getInstance（）。getReference（）; ref.addListenerForSingleValueEvent（new ValueEventListener（）{ @Override $ b $ public void onDataChange（DataSnapshot dataSnapshot）{$ b $ if（dataSnapshot.exists（））{ double location_left = dataSnapshot.child（location_left）。getValue（Double.class）; double location_right = dataSnapshot.child（location_right）。getValue（Double.class）; LatLng sydney = new LatLng（location_left，location_right）; mMap.addMarker（new MarkerOptions（）。position（sydney）.title（Marker in Sydney））; mMap.moveCamera（CameraUpdateFactory.newLatLngZoom（sydney ，18））; } else { Log.e（TAG，onDataChange：No data）; } } @Override public void onCancelled（DatabaseError databaseError）{ throw databaseError.toException（）; } }）; I want to retrieve location markers from firebase database but I can't see any markers after running this code. I tried to make EventListener but the map runs without any markers. This my code:public class MapsActivity extends FragmentActivity implements OnMapReadyCallback { private GoogleMap mMap; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_maps); // Obtain the SupportMapFragment and get notified when the map is ready to be used. SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager() .findFragmentById(R.id.map); mapFragment.getMapAsync(this); } /** * Manipulates the map once available. * This callback is triggered when the map is ready to be used. * This is where we can add markers or lines, add listeners or move the camera. In this case, * we just add a marker near Sydney, Australia. * If Google Play services is not installed on the device, the user will be prompted to install * it inside the SupportMapFragment. This method will only be triggered once the user has * installed Google Play services and returned to the app. */ @Override public void onMapReady(GoogleMap googleMap) { mMap = googleMap; DatabaseReference ref = FirebaseDatabase.getInstance().getReference(); String rightLocation = ref.child("location_right").toString(); String leftLocation = ref.child("location_left").toString(); double location_left = Double.valueOf(leftLocation); double location_right = Double.valueOf(rightLocation); LatLng sydney = new LatLng(location_left, location_right); mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney")); mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(sydney,18)); // Add a marker in Sydney and move the camera }}What might be wrong here? 解决方案 You need to use a ValueEventListener to obtain data from the Firebase database. This is explained in the documentation.@Overridepublic void onMapReady(GoogleMap googleMap) { mMap = googleMap; DatabaseReference ref = FirebaseDatabase.getInstance().getReference(); ref.addListenerForSingleValueEvent(new ValueEventListener() { @Override public void onDataChange(DataSnapshot dataSnapshot) { if (dataSnapshot.exists()) { double location_left = dataSnapshot.child("location_left").getValue(Double.class); double location_right = dataSnapshot.child("location_right").getValue(Double.class); LatLng sydney = new LatLng(location_left, location_right); mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney")); mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(sydney,18)); } else { Log.e(TAG, "onDataChange: No data"); } } @Override public void onCancelled(DatabaseError databaseError) { throw databaseError.toException(); } }); 这篇关于如何从firebase数据库添加谷歌地图标记的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！