java - Firebase Cloud Firestore - 将文档获取到自定义对象并将其传递给另一个 Activity

Question

我正在尝试将存储在 Firebase Cloud Firestore 中的文档保存到我的自定义对象(动物)中。我需要将此对象传递给另一个 Activity 。我使用了 intent.putextra("class name", obj) 函数，但我无法访问我创建的用于获取文档的对象。这是我的代码:

public void start(View view){

String id;
EditText animalIdEditText = findViewById(R.id.animalIDsearch);
String animalId = animalIdEditText.getText().toString();
FirebaseFirestore db = FirebaseFirestore.getInstance();
DocumentReference docRef = db.collection("Animals").document(animalId);
docRef.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
    @Override
    public void onSuccess(DocumentSnapshot documentSnapshot) {
        Animal animal = documentSnapshot.toObject(Animal.class); // this is where I create animal object. It doesn't let me declare it above either.
    }
});

    Intent intent = new Intent(this, searchActivity.class);
    intent.putExtra("Animal",animal); // error in this line : animal  can't be resolved
    startActivity(intent);
}

Answer 1

要解决这个问题，您需要等待数据，为此，您需要像这样创建一个自定义回调:

public interface MyCallback {
    void onCallback(Animal animal);
}

然后您需要创建如下所示的方法:

public void readData(MyCallback myCallback) {
    String id;
    EditText animalIdEditText = findViewById(R.id.animalIDsearch);
    String animalId = animalIdEditText.getText().toString();
    FirebaseFirestore db = FirebaseFirestore.getInstance();
    DocumentReference docRef = db.collection("Animals").document(animalId);
    docRef.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
        @Override
        public void onSuccess(DocumentSnapshot documentSnapshot) {
            Animal animal = documentSnapshot.toObject(Animal.class);
            myCallback.onCallback(animal);
        }
    });
}

最后，只需简单地调用 readData() 方法并将 MyCallback 接口(interface)的实例作为参数传递给您在 Activity 中需要的任何地方，如下所示:

readData(new MyCallback() {
    @Override
    public void onCallback(Animal animal) {
        Intent intent = new Intent(this, searchActivity.class);
        intent.putExtra("Animal", animal);
        startActivity(intent);
    }
});

更多信息可以看我在this post的回答 以及此 video .