Question

我试图显示在线商店和离线商店，但问题是它完美地显示了商店，但是当我单击“开/关”开关按钮时，标记将同时显示绿色和红色两种颜色

    public void onMapReady(GoogleMap googleMap) {
   map=googleMap;
    if (ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(getActivity(),new String[]{Manifest.permission.ACCESS_FINE_LOCATION},1);
    }
    map.setMyLocationEnabled(true);
    databaseReference.orderByChild("action").equalTo("open").addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
       for(DataSnapshot shops:dataSnapshot.getChildren() )
       {
           shoplocation shop=shops.getValue(shoplocation.class);
           LatLng sydney = new LatLng(Double.parseDouble(shop.getLat()),Double.parseDouble(shop.getLon()));
           map.addMarker(new MarkerOptions().position(sydney).title(shop.getShopname()).icon(BitmapDescriptorFactory.defaultMarker(
                   BitmapDescriptorFactory.HUE_GREEN
           )));
           map.moveCamera(CameraUpdateFactory.newLatLng(sydney));


       }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

    databaseReference.orderByChild("action").equalTo("close").addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for(DataSnapshot shops:dataSnapshot.getChildren() )
            {
                shoplocation shop=shops.getValue(shoplocation.class);
                LatLng sydney = new LatLng(Double.parseDouble(shop.getLat()),Double.parseDouble(shop.getLon()));
                map.addMarker(new MarkerOptions().position(sydney).title(shop.getShopname()).icon(BitmapDescriptorFactory.defaultMarker(
                        BitmapDescriptorFactory.HUE_RED
                )));
                map.moveCamera(CameraUpdateFactory.newLatLng(sydney));


            }

这是开/关商店的一面 The part where shops are on/off

Answer 1

在您的ValueEventListener中，您总是添加新标记。但是切勿删除已添加的内容。
因此，当数据更改时，您可以在已添加的标记上方添加新的标记。

在添加红色和绿色标记之前，请先删除所有标记，然后才能开始制作ValueEventListener。

类似（未经测试）的东西

@Override
public void onDataChange(DataSnapshot dataSnapshot) {
  googleMap.clear()
  for(DataSnapshot shops:dataSnapshot.getChildren() )
  {
    shoplocation shop=shops.getValue(shoplocation.class);
    LatLng sydney = new LatLng(...);
    map.addMarker(...);
    map.moveCamera(CameraUpdateFactory.newLatLng(sydney));
  }
}

无法在地图上显示在线和离线用户

1 个答案: