java - 如何避免两个类之间的循环依赖？

Question

我有两个类 - 一个定义 BaseActivity (应用程序中所有 Activity 的全局父级)，另一个是 AsyncTask 类，我在其中定义了常见的网络操作。但我有下一个问题。 onPostExecute() 方法中名为 RestfulNetworkTasks 的 AsyncTask 类必须调用 UpdateCurrentActivityAfterNetworkOperation() (在 中定义) BaseActivity 类，但 BaseActivity 类还必须创建 RestfulNetworkTasks 的实例。下面的代码清楚地说明了这个问题。

class RestfulNetworkTasks extends AsyncTask<Pair<String, LinkedHashMap<String, Object>>, Void, LinkedHashMap<String, Object>> {
    private ImmutableMap<String, Object> serverData_;
    NetworkOperation LowLevelRestOperations_ = new NetworkOperation();

    @Override
    protected LinkedHashMap<String, Object> doInBackground(Pair<String, LinkedHashMap<String, Object>>... params) {
        return LowLevelRestOperations_.executeServerCommand(params[0].getValue0(), params[0].getValue1());
    }

    protected void onPostExecute(LinkedHashMap<String, Object> result) {
        serverData_ = copyOf(result);
        BaseActivity instance_Activity = new BaseActivity(); 
        //BaseActivity injection (It is too bad to create Activity in such a way - I know!) So I need some piece of advice
        instance_Activity.UpdateCurrentActivityAfterNetworkOperation(serverData_);
        //Here I must call method for updating GUI after operation
    }

    public ImmutableMap<String, Object> GetDataFromServer() {
        return serverData_;
    }
}

public class BaseActivity extends Activity {

    RestfulNetworkTasks serverOperation_ = new RestfulNetworkTasks(); //RestfulNetworkTasks injection

    public void UpdateCurrentActivityAfterNetworkOperation(
        ImmutableMap<String, Object> server_data) {
    }// Here is this method which I will override in my child activities

    @SuppressWarnings("unchecked")
    public ImmutableMap<String, Object> Login(LinkedHashMap<String, Object> parameters) {
        Pair<String, LinkedHashMap<String, Object>> params_ = new Pair<String, LinkedHashMap<String, Object>>(LOGIN_COMMAND, parameters);
        serverOperation_.execute(params_);
        return serverOperation_.GetDataFromServer();
    }
}

如您所见，我在 RestfulNetworkTasks 和 BaseActivity 类之间存在循环依赖关系，这可能会导致构造函数的无限链调用。

问题是如何重构这个设计来避免这种情况？

Answer 1

AsyncTask 几乎总是从 Activity 中调用，那么为什么不将其作为构造函数参数传递呢？

RestfulNetworkTasks.java:

private BaseActivity activity;

public RestfulNetworkTasks(BaseActivity activity){
    this.activity = activity;
}

BaseActivity.java:

new RestfulNetworkTasks(this).execute();