Question

我必须将响应从firebase返回到另一个函数，该函数将使用该数据进行进一步处理。

public ArrayList<String> getDatas(String number) {
    final ArrayList<String> requestList = new ArrayList<>();

    final FirebaseDatabase database = FirebaseDatabase.getInstance();
    final DatabaseReference reference = database.getReference("Users").child(number).child("request_list");

    final DatabaseReference requestReference = database.getReference("Request");

        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                Log.i(TAG, "onDataChange: ");
                for (final DataSnapshot data : dataSnapshot.getChildren()) {
                    Log.i(TAG, "onDataChange: data: " + data.getValue());
                    requestList.add(data.getValue().toString());
                }
                Log.i(TAG, "onDataChange: for ended");
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
    return requestList;
}

由于firebase操作是异步的，我无法等待数据返回。有人可以帮我解决这个问题吗？

Answer 1

您可以使用回调方法

http://developer.android.com/reference/java/util/concurrent/Callable.html

通过使用Callable接口，您可以将参数作为函数传递，我添加了一个简单的代码片段以便理解。

public class MainActivity<V> extends Activity {


    Callable<String> doLogin=null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        doLogin=new Callable<String>() {  //created but not called now.

            @Override
            public String call() throws Exception {

                //make some piece of code
                return "something"; //or false
            }
        };

        CheckSession checkSession=new CheckSession("sessionName");
        String sessionKey="";


        try {  //we are sending callable to the DAO or any class we want 
             sessionKey=checkSession.getSessionKey(doLogin);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}



public class CheckSession{


    String sessionName="";
    Callable<String> func=null;

    public CheckSession(String sessionName) {
        super();
        this.sessionName = sessionName;

    }

    public String getSessionKey(Callable<String> doLogin) throws Exception{

        func=doLogin;

        return (String) func.call();

    }

}

如何处理firebase中的异步调用

1 个答案: