如何在Fire Store中查询集合的所有文档 [英] How do query all documents of a collection in Fire Store

问题描述

我正在尝试在Google地图上显示Cloud Firestore的信息.我可以使用以下代码在文档中应用标记，但是我需要显示多个文档.

I am trying to display information from Cloud Firestore on Google maps. I am able to apply a marker from a document using the below code, however I have multiple documents that I need to display the data from.

下面是当前代码，正如我所说的，它成功显示了一个文档中带有信息的标记，但是每个文档都包含一个需要在地图上显示的不同位置.

Below is the current code and as I said it successfully displays a marker with info from one document, however every document contains a different location that needs to be displayed on the map.

    private void addMapMarkers(){

    FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
    CollectionReference pointsRef = rootRef.collection("notes");
    DocumentReference docRef = pointsRef.document("u20UmWSrlP0EiZH9CNP3");
    docRef.get().addOnCompleteListener(new 
    OnCompleteListener<DocumentSnapshot>() {
        @Override
        public void onComplete(@NonNull Task<DocumentSnapshot> task) {
            if (task.isSuccessful()) {
                DocumentSnapshot document = task.getResult();
                if (document.exists()) {
                    String latitude = document.getString("Latitude");
                    String longitude = document.getString("Longitude");
                    String name = document.getString("Attraction Name");

                    float lat = Float.parseFloat(latitude);
                    float lng = Float.parseFloat(longitude);

                    LatLng latLng = new LatLng(lat, lng);
                    mMaps.addMarker(new 
                    MarkerOptions().position(latLng).title(name));
                }
            }
        }
    });
}

数据库结构如下:

推荐答案

要获取所有文档的纬度和经度属性的值，只需使用以下几行代码:

To get the values of your latitude and longitude properties of all documents, simply use the following lines of code:

FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
CollectionReference notesRef = rootRef.collection("notes");
notesRef.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
    @Override
    public void onComplete(@NonNull Task<QuerySnapshot> task) {
        if (task.isSuccessful()) {
            for (QueryDocumentSnapshot document : task.getResult()) {
                float lat = Float.parseFloat(document.getString("Latitude"));
                float lng = Float.parseFloat(document.getString("Longitude"));
                String name = document.getString("Attraction Name");
                LatLng latLng = new LatLng(lat, lng);
                mMaps.addMarker(new MarkerOptions().position(latLng).title(name));
            }
        }
    }
});

因此解决此问题的关键是使用 task.getResult()，它可以帮助您遍历 QueryDocumentSnapshot 对象.

So the key for solving this problem is the use of task.getResult() that can help you iterate through the QueryDocumentSnapshot object.

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