Android 如何在代码中等待所需数据从firestore下载？

我可以从firestore数据库读取数据，但我不能在代码中等待整个数据加载。所以现在发生的是，我的代码甚至在实际加载所需数据之前就向前执行。我想知道如何在从firestore读取数据时等待，一旦数据被提取，那么只执行其他代码。我的代码片段

public void getFoodMenu(String clientID){
    clientFullMenu.clear();
        DocumentReference docRef = mDatabase.collection("MenuDetails").document(clientID);
        docRef.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
            @Override
            public void onSuccess(DocumentSnapshot documentSnapshot) {
                if(documentSnapshot.exists()){
                    String sMenuCurrency  = documentSnapshot.getString("menu_currency");
                    colRefMenuType = docRef.collection("MenuType");
                    colRefMenuType.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
                        @Override
                        public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
                         List<DocumentSnapshot> menuTypeDocuments =  queryDocumentSnapshots.getDocuments();
                         for(int i=0; i<menuTypeDocuments.size();i++){
                             DocumentSnapshot menuTypeDoc = menuTypeDocuments.get(i);
                             String sMenuType = menuTypeDoc.getId();
                             String sSubMenuPriority  = menuTypeDoc.getString("priority");
                             Log.i("XXXX","document::"+menuTypeDoc.getId()+", priority::"+sSubMenuPriority);
                             colRefMenuItems = colRefMenuType.document(sMenuType).collection("MenuItems");
                             colRefMenuItems.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
                                 @Override
                                 public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
                                    List<DocumentSnapshot> menuItemDocuments = queryDocumentSnapshots.getDocuments();
                                    for(int  j=0;j<menuItemDocuments.size();j++){
                                        DocumentSnapshot menuItemDoc = menuItemDocuments.get(j);
                                        String sFoodItemID = menuItemDoc.getId();
                                        String sFoodItemPriority = menuItemDoc.getString("food_item_priority");
                                        String sFoodItem  = menuItemDoc.getString("food_item");
                                        String sFoodItemDesc = menuItemDoc.getString("food_item_description");
                                        String sImageUrl  = menuItemDoc.getString("food_item_image_location");
                                        String sFoodItemPrice = menuItemDoc.getString("food_item_price");
                                        Log.i("XXXX","FoodItem::"+menuItemDoc.getId()+", priority::"+sFoodItemPriority);
                                        boolean  bMenuType = false;


                                        FoodMenu menu = new FoodMenu();
                                        menu.sFoodItemID = sFoodItemID;
                                        menu.sFoodItem = sFoodItem;
                                        menu.sFoodItemDesc  = sFoodItemDesc;
                                        menu.sFoodMenuCurrency = sMenuCurrency;
                                        menu.iFoodItemPrice = Integer.parseInt(sFoodItemPrice);
                                        menu.sImageUrl = sImageUrl;
                                        menu.sMenuItemPriority = sFoodItemPriority;

                                        //code to add the item under its corresponding food menu type (viz BREAKFAST, LUNCH, DINNER) in case it already exists
                                        for (int i = 0; i < clientFullMenu.size(); i++) {
                                            Log.i("MainActivity","clientFullMenu.get(i).sMenuType:" + clientFullMenu.get(i).sMenuType+" ,sMenuType:"+sMenuType);
                                            if (clientFullMenu.get(i).sMenuType.equalsIgnoreCase(sMenuType)) {
                                                clientFullMenu.get(i).subFoodMenu.add(menu);
                                                bMenuType = true;
                                            }
                                        }
                                        //code to add a new arraylist of food menu type (viz BREAKFAST, LUNCH, DINNER) in case it doesn't exist already
                                        if (!bMenuType) {
                                            ClientFullMenu clientSubMenu = new ClientFullMenu();
                                            clientSubMenu.sMenuType = sMenuType;
                                            clientSubMenu.sMenuPriority = sSubMenuPriority;
                                            ArrayList<FoodMenu> subFoodMenu = new ArrayList<FoodMenu>();
                                            subFoodMenu.add(menu);
                                            clientSubMenu.subFoodMenu = subFoodMenu;
                                            clientFullMenu.add(clientSubMenu);
                                            Log.i("XXXX","Final clientFullMenu.size()1:" + clientFullMenu.size()); //it prints the correct size
                                        }

                                    }
                                 }
                             });

                         }
                        }
                    });
                }
            }
        });
    Log.i("XXXX","Final clientFullMenu.size()2:" + clientFullMenu.size()); //It prints size as 0
}

public void getFoodMenu（字符串clientID）{
clientFullMenu.clear（）；
DocumentReference docRef=mDatabase.collection（“菜单细节”）.document（clientID）；
docRef.get（）.addOnSuccessListener（新的OnSuccessListener（））{
@凌驾
成功时公共无效（文档快照文档快照）{
if（documentSnapshot.exists（））{
String sMenuCurrency=documentSnapshot.getString（“菜单\货币”）；
colRefMenuType=docRef.collection（“MenuType”）；
colRefMenuType.get（）.addOnSuccessListener（新OnSuccessListener（））{
@凌驾
成功时公共无效（QuerySnapshot QueryDocumentSnapshot）{
列表菜单TypeDocuments=queryDocumentSnapshots.getDocuments（）；
对于（int i=0；我将
Log.i（）
行移动到
onSuccess（）
中。