对于下面给出的代码，字符串 receivedResponse 从接口函数调用时不会立即指定。我发现，分配字符串 response 在 receivedResponse ，我必须调用函数 onCurrentResponse() 再一次。我将非常感激知道背后的原因。如果有可能以某种方式解决这个问题，那就更好了。以下代码足以再现错误。请看一下：

public class MainActivity extends AppCompatActivity {
private NetworkManager networkManager;
String receivedResponse;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    networkManager = new NetworkManager(this);
}

public void handleClick(View view){
    networkManager.getResponseFromNetwork(callback);
    System.out.println("Response in 'receivedResponse' is: " + receivedResponse); // I am getting 
//null value when called for the first time

}
private final NetworkManager.ServiceCallback callback = new NetworkManager.ServiceCallback() {

    @Override
    public void onCurrentResponse(@NonNull String response) {
        receivedResponse = response; // I have to call this function again to assign the response 
 string
        System.out.println("Response in 'response' is: " + response);
    }
};
}

class NetworkManager {
private final RequestQueue queue;
public NetworkManager(@NonNull final Activity activity) {
    queue = Volley.newRequestQueue(activity.getApplicationContext());
}
public interface ServiceCallback {
    @MainThread
    void onCurrentResponse(@NonNull final String response);
}
public void getResponseFromNetwork(final ServiceCallback callback) {
            final String url = "https://www.themealdb.com/api/json/v1/1/random.php";
    StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
            callback::onCurrentResponse, error -> System.out.println("Some error")
    );
    queue.add(stringRequest);
}
}