在Android应用的Firebase数据库中检索子arraylist

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值强制转换为ArrayList：

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