android - 在 Android 应用程序的 firebase 数据库中检索子数组列表

Question

我想知道如何检索数据请帮忙!谢谢。

这是我在文件库中的数据库结构。

 mDatabase = FirebaseDatabase.getInstance().getReference().child("chinese");
    mDatabase.keepSynced(true);

    mDatabase.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot childDataSnapshot : dataSnapshot.getChildren()) {
                Log.v(TAG,""+ childDataSnapshot.getKey()); //displays the key for the node
                Log.v(TAG,""+ childDataSnapshot.child("ingredient").getValue());   //gives the value for given keyname
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

Answer 1

mDatabase = FirebaseDatabase.getInstance().getReference().child("chinese");
mDatabase.keepSynced(true);

mDatabase.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot childDataSnapshot : dataSnapshot.getChildren()) {
                if (childDataSnapshot.child("ingredient").getValue() != null) {
                    ArrayList<String> ingredients = new ArrayList<>();
                    for (DataSnapshot ing : childDataSnapshot.child("ingredient").getChildren()) {
                        ingredients.add(ing.child("ingredient").getValue(String.class));
                    }
                    System.out.println("Gained data: " + ingredients.toString());
                }
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});

另一种方法是将 DataSnapshot 值转换为 ArrayList:

GenericTypeIndicator<ArrayList<String>> t = new GenericTypeIndicator<ArrayList<String>>() {};
ArrayList<String> ingredients = childDataSnapshot.child("ingredient").getValue(t);