java - 使用 Android Studio 和 Firebase 在 Spinner 中获取其选定子值的键

Question

我试图通过允许用户从 Spinner 中进行选择来获取某个子值的键。

微调器有“Product_Name”值作为其选择。通过选择其中一个，程序应该获取其 key 并使用它来获取另一个子值以供其他用途。

示例:

产品-> -LoUXnfUCEj4k4A3dkte-> 产品名称:“牛排”

通过在微调器中选择“Steak”，我必须获得“-LoUXnfUCEj4k4A3dkte”

    databaseRefSelectItem = FirebaseDatabase.getInstance().getReference("PRODUCTS");

    final DatabaseReference mDatabase = databaseRefSelectItem;
    mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull final DataSnapshot dataSnapshot) {
            //We create an array list to hold the values brought from the database and show them in the spinner
            final List<String> titleList = new ArrayList<String>();

            for(final DataSnapshot snapshot : dataSnapshot.getChildren()) {

                titleProduct = snapshot.child("Product_Name").getValue(String.class);

                //populate the spinner with that array list
                ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(AddTransactionActivity.this, android.R.layout.simple_spinner_item, titleList);
                arrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                selectProduct.setAdapter(arrayAdapter);

                titleList.add(titleProduct);

                //Click event for each spinner element
                selectProduct.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                    @Override
                    public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                        //pass the reference from that value into another snapshot in order to query those values, here you need to get your node id and inside just get your number , name and so on
                        selectItem = titleList.get(i);

                        mDatabase.child(selectItem).addValueEventListener(new ValueEventListener() {
                            @Override
                            public void onDataChange(final DataSnapshot dataSnapshot2) {

                                key = dataSnapshot2.getKey();

                                currentItemStock = dataSnapshot2.child(key).child("Current_Stock").getValue(String.class);
                                currentStk.setText(key);

                            }

                            @Override
                            public void onCancelled(@NonNull DatabaseError databaseError) {
                            }
                        });
                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> parent) {
                    }
                });
            }
        }
        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
        }
    });

如何获得“-LoUXnfUCEj4k4A3dkte”？

注释:-LoUXnfUCEj4k4A3dkte是随机生成的。

Answer 1

使用.getKey()获取快照的 key ，例如:

for(final DataSnapshot snapshot : dataSnapshot.getChildren()) {
    if (snapshot.child("Product_Name").getValue(String.class).equals("Steak")){
        String theKey = snapshot.getKey(); //This will return -LoUXnfUCEj4k4A3dkte
    }
}

将返回该引用处快照的键。